DAYLIGHT FLUORESCENT PIGMENTS

IN WORKS OF ART

Properties, History, and Fading

by

AKEMI YOSHIZAWA

A thesis submitted to the Department of Art

in conformity with the requirements for

the degree of Master of An Conservation

Queen's University

Kingston, Ontario, Canada

October, 3000

Copyright O AKEMI YOSHIZAWA, 2000

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Abstract

Understanding daylight fluorescent pigments is the objective of this research; however, the thesis includes

[heortftical study on colour science. fluorescence and instrumental analysis o f colours a s background

knoivledge. The historical background o f fluorescent pigments is also studied. Modern colour specification

systems are rrviewed.

The ssperiments were focused to collect data o n the optical properties of daylight fluorescent pigments. In

the first experirnent. daylight fluorescent pigments were subjected to acceierated deterioration under intense

illumination. and the deterioration characteristics of those pigments were monitored with the changes on

their reflectancs spectra. In rhe second experiment. the reaction of daylight fluorescent pigments to

monochromatic light was investigated at each waveiength of excitation radiation by means of

spectrophotornetry. In both the firsr and the second experiments. the results were compared between the

uncsposed and exposed samples, and among differenr coIours. In the third experiment, the daylight

tluorescent pigments were observed under a UV lamp to tùnher characrerise their oprical properties.

This study was also concerned with t h e conservation methods for materials char consist o f dayiight

fluorescent pigments. On the o n e hand. it is difficult CO predict hotv daylight fluorescent pigments will

deteriorate in the future. and o n the other hand. appropriare materials are not always found CO match the

colours of daylight fluorescent pigments during conservation ueatment o f deteriorated objects-

Attempts were made to collect information directly from an conservation professionals and colorant

manufacturers. The experience of art conservators in the treatment o f works with dayiight fluorescent

pigments and some technical information from manufacturers were compiled 3s case studies and

suggestions.

I t was proven thrit colour deterioration of daylight fluorescent pigments proceeds quickly at the early stage

of light exposure but the deterioration rate slows down afrer the initial progression. and the application of

UV filtors is effective for prevsnting light damrise on daylight tluorescent pigments. Thus data obtriined in

this study helps conservation professionais in predicting the frite o f objects made with daylipht fluorescent

pigments and in mriking decisions about the rnsthods o f preventive conservation a d o r conservation

treatment that they will choose.

Acknowledgements

Upon cornplrtion of this thesis, 1 uish ro express gratitude to people and organizations that have supponed

this study dirrctly and indirectly. This project procceded undrr co-supervision between the Master of An

Conservation Prosram at Quecn's University (Kingston, Canada) and the Canadian Conservation Instituts

( Orttl\vri. Canada).

Barbara Ksyser. late Professor of Paintins Conservation for the Master of Art Conservation Program at

Queen's University. suggested the topic of this thcsis and supponed this study as the first supsrvisor. This

thesis hurnbly cornmernorates her dedication ro art conservation.

Oram at Krysiri Spirydowicz. Professor of Artihcts Crmservation for the Master of Art Conservation Pro,

Quscn's University. has guided and edited this thcsis as the îinal supsrvisor of the entire project.

Stefan h.1ichalski. Senior Conservation Scientist at the Canadian Conservation Institute, supervised al1

expsriments for rhis study. He arranged the facilities and personne1 to accornmodatr these experiments. and

hc has given ridvised on the scientific content of this thesis.

oram There \vas continuous heIp from the faculty msmbsrs of Queen's University Art Conservation Proe

while many scientists. consenvators, librarians, technical, non-technical and administrative staff at the

Crinadian Conservation Institute were involved in this project and offered unwavering suppoit:

Queen's Universitv

Dorothea Burns

Alison Murray

Ian I-iodkinson

Chriscine Adams

Canadian Conservation lnsritute

Srason Tse

Maurcen MacDonald. Nancy Binnie. Leslie Carlyle

Jane D o w , Lyndsic Sels.)-n

Bob Arnold, Debra Daly Hanin. Helzn McKay

:\manda Gray

Insrid O'shca

Sonya MiIly. Charlie Costriin. David Grattan

XIiciri Prata. l'icki Davis. Lucie Forgucs. Sumi Grover

..\II my clrtss marcs at Qucen's University and che interns at the Canadian Conservation Institute also

supported this study and providsd information. Elizabeth Jablonski. Flora Davidson and Karen Osborne

contrihuted 3 pea t dcal to this study.

Thanks ro the Department of Art a t Quren's University for genrrril support and to the School of Graduatc

Studies and Reserirch for financial suppon. Susan Anderson and other staff of the international Centre at

Quern's University supponed my life as a siudrnt at Queen's University. The staff of the Writing Centre

edited this thesis.

Chris Bozstadt of Tri Art blanufacturing Incorporated (Kingston. Canada) contributed some of the sarnples

uscd in this study. He also providsd information on pipwnrs. A lot o f technicd information was offsred

Ïrom Golden Arrist Colors. Inc. (U.S.A.).

Finally. many people kindly provided infornxiion for this nudy:

E- J. Baxtcr (Carnegie Museum of Art & The Andy Warhol Museum. USA.)

M. N. Challan Belval ( M d e d'art contemporain de Montréal. Canada.)

hl. Fi. Ellis (Ne-.Y York University. USA.)

R. Ganier (National Gallery o f Canada, Canada.)

M. Goldmann (New York University. USA.)

This thcsis is ont: academic study. No person or body shall be disadvantaged in any way based on

information contained in this thesis.

This thesis was written for a master's dcgrec in art conservation science: at the same time. it is a report to

the Canndinn Conscrvrttion institute on the experimcnts to investigate the properties of daylight tluorescrnt

pigments. The cxpcriments for this thesis \vere conducted as the Institutc's intsrnship projecr. therefore. the

results of the expcrimcnts had to be presentrd in a uay thar rnriblcs a further data analysis by the Insritute.

For this rerison, the part o f "r.~periments" and p p h s in this thesis contain information that is not critical

for gcncrd reriders but is necsssat-y for the Crinadian Conservarion Institute to ticccss the data.

In the field of a n conservation. sorne everyday words have specitic rneanings. The use of the technicd

ttrrns appear in this thesis sire defined in the "Glossary" to heIp the readers who might not be familirir with

art conservation and colour science. 1 hope this thesis is read by mriny people inciuding studsnts. tsachers

and profcssionrils who work in the fields of art. humanity and science.

Preface

Barbara Keyser, adviser for this project. told me that the c a t s p r y of daylight fluorescent pisments hrid nor

bccn studisd enough in the fisid o f an conservation. Sht. thought that i f 1 would study about t h o x

pigments. any discovery 1 make would contriburr: to the knowkdge of art conservation. Sht: also said thrit

the proccss of rnp reserirch itsrlf \vould be \\orth reporting ro hslp Iater studics. 'To know uhrit is daylight

tluorescent pigment from consrrvation perspective" was the starting point and the goal of my srudy on

daylight fluorescent pi, ~rnents.

Table of Contents

Abstrsict .................... .. ... ... 1. ............................................................................

... .......................................................................................... tlcknowlcdgemcnts I I r .

Prefacc ......................................................................................................... vi .

Table of Contents ........................................................................................... ~ i i .

List of Tables ............................................................................................... s i i .

... List of Figures .............................................................................................. ult .

1 . Introduction .............................................................................................

2 . Theory and History of Daylight Fluorcsccnt Pigments ......................................... 3 .

........................................................... 2 . 1 . T h s o r). of Daylight Fluorescent Pigments

......................................................................... 2 . 1 . 1 . Word Definitions in Brirf

................................................... 2 . 1 . 2 . Driylight Fluorescent P i ~ r n e n t s ris a h. laterial

............................ Daylight Fluorescent Pigments . Over Vit.\ v . Glow Without Battery

......................................................................................... Visuil Propenirs

Spectrophotornetric Signiticrince ......................................................................

...................................................... Applications of Daylight Fluorescenr Pigments

....................................... Causes of Deterioration in Driylight Fluorescent Colorants

Mrtnufcicturc of Daylisht Fluorescent Pigments ....................................................

Causes o f Fluorescence ..................... .... .....................................................

Mechrinism of Fluorcsccnce ..........................................................................

......................................... Quenchiny . Sensitising, and Enhancinp of Fluorescence

.............................................. 2 . 1 . 3 . Fiuorcscent Brishtencrs ...................... ....

..................................................... ....................... Basic Chcirxteristics ....

.................................................. hldrcular Structures of Fluorescent Brishteners 20 .

................................................... Application of Fluorescent Brightcners to P a p a 21 .

2 . 1 . 4 . Health Issues o f Driylight Fluorescent XIriteririls ............................................... --. 7-1

2 . I . 5 . Uses o f Daylight Fluorescent Colours ......................................................... 23.

A n and Design .......................................................................................... 23.

............................... Tcxrile D'es .................................................. . 21-

Science and Technology .............................................................................. 21 .

2 . 3 . History .................................................................................................. 25 .

............................................................. 2 . 2 . 1 . History of Luminescent Substances 25 .

............................................................................... The Days of Alchernisis 25 .

The Days of Industrial and Scirnrific Revolutions ................................................ 25.

....................................................................... The Days of High Trchnology 27 .

................................ 2 . 2 . 2 . History of Driylight Fluorescent Pigments ... . . . . . . . . . . . 29 .

............................................................................... 2 . 2 . 3 . History of Day-Glo 31 .

3 . Colour Science ............................................................................ . . . . . . . 36-

3 . 1 Colour Theory ..........................................................................................

3 . 1 . 1 . History of Cotour Theory ........................................................................

3 . 1 . 2 . Colour Systems .................................... .... ............................................

h.funsell's Colour Theory

From Maxwell's Triangle

..............................................................................

.................................... to the CIE Chrornaticity Dirigram

CIE (L*u*v*) and CIE (L*a*bc) .....................................................................

............................................................ Calcula~ion fbr the CIE Colour Systrms

3 . Important Concepts in Colour Theory

Huc . Value . and Chroma ...................

Mising Colours ........................................................................................ 55 .

.................................................................. Colour Circle and Primriry Colours 57 .

............................................................ \Ifhrit =lffects the Appearrince o f Colour 5s .

............................................................................................. blerrirnerism 5 s .

........................................................... Lighr ris an Electrornagnrtic Phenornenon 61 .

................... ................. Transmission . Absorption . Retlection . and Fluorescence .. 63 .

................................................................................. . . . 3 3 Colour Merisurement 68

................................................................................. 3.1. Bluc-Wool Standards 75 .

1 . Esperimcnts ................................ ... ...................................................... 80-

.................................................................................... 4 . 1 . Accelerrited Fading

4 . 1 . I . Introduction ......................... .... ..........................................................

4 . 1 . 2 . Objective o f This Experirnent .................................. ... ......................

4 . 1 . 3 . Experirnental Set Up ..............................................................................

...................................................................... ................. Outline .........

.................................................................................... Sample Preparation

Sunlisht Exposure .....................................................................................

Alternative Settings Exposure ........................................................................

Measurement ................... .... .. .......................................................... .....

.......................................................... Facility and Location ...................... ..

4 . 1 . 4 . Results ............................. ..... ............................................................

4 . 1- 5 Discussion ..........................................................................................

4 . 1 . 6 . Conclusion ........................................................................................ 95 .

............................... 4 . 1 . 7 . Supplemrntril Information About ihs Experimcntal Settings 96 .

4 . 2 . Andysis of Optical Propenies: measurcment of the excitation wavelengths and the fluorescensc

.......................................................................................... ~vrivslengths

.................................................................. 4 . 2 . 1 . Objective o f This Expc'rimcnt

4 . 2 . 2 . Enperimental Set U p ............................................................................

................................................................................................. Outline

................................................................................... Sample Preparation

.................................................................................. Retlsctance Spectra

........................................................................ Excitation-Ernission Spectra

................................................................ blonochromaric Excitation Spectra

................................................................................. Fricility and Location

4 . 3 . 3 . Rrsults .............................................................................................

4 . 3 . 1 . Discussion .........................................................................................

4 . 3 . 5 . Conclusion ........................................................................................

....................................................... 4 . 3 . Identifying Daylight Fluorescent Materials

.................................................................. 4 . 3 . 1 . Objective o f This Experirnent

............................................................................ 4 . 3 . 2 . Experimental Set Up

................................................................................................. Outline

Saniple Prepriration ...................................................................................

Facility and Location .................................................................................

4 . 3 . 3 . Results ................... .... .... .. ............................................................

4 . 3 . 3 . Discussion ........................................................................................

4 . 3 . 5 . Conclusion ....................... ......... ........................................................

................................................... 5 . Case Studies and Conservation Suggestions 1 14 .

... . 5 . 1 . Culour Deterioration of Daylight Fluorsssrnt I'igrnrnts . Other Enperirnrnts Rrported 1 14

-................. . 5 . 2 . Cases of Conservation Treritment and Prevsntive Conservation Measures 118

............................................................................................. 5 . 3 . Discussion 122 .

................................................................. 6 . Conclusion ................... .... 125 .

....................................................................................... 6 . 1 . Final Summary 125-

6 . 2 . Sug_aestions for Later Studirs ................... .. ................................................ 128 .

........................................... ............................................ Bibliography ..... 129 .

......................................................... Books and Articles ................... ... 129 .

............................................................ Dictionaries . Hrindbooks and Indices 133 .

............................................................... Standards and Product Litcrriturr 134-

Informa1 Sources of Information on Conservation Treatment and Preventive Conservation of

.................................................................. Daylight Fluort=scent Matcriais 136 .

.................................................................................................. Appendices 138 .

1 . Applications of Fluorescent Colours in Science and Tcchnologg .......................... 139 .

............................................................................. I I . Natural Colour System 143-

.............................. . I I 1 . Suggestions for Handling of Daylight Fluorescent hfaterials 138

................................................................. ....................... IV . Tables ..... 151 .

..................................................................... ......................... V . Figures .. 173 .

List of Tables

Gensral Solubility Characteristics of Standard Organic Flucircscent Pigments: Table 1 ..........

chicle les Suitablc for Pigmentation \vith Orgrinic fluorescent Pigments: Table 2 .................

Dyes 3s Cornponents of Driyliglit Fluorescent Pigments: Table 3 ...................................

Xlanufactursrs of Daylight Fluorescent Pisments: Table 4 ...........................................

Colour Spectrurn: Table 5 ..................................................................................

Colour hlixture: Table 6 ...................................................................................

Fi ftcen Causes of Colour: Table 7 ........................................................................

Instrument List for Experimenrs: Table S ...............................................................

Samplr List - Sunlisht Esposure: Table 9 ..............................................................

Sarnpls List - Alternative Scttings exposure: Table 10 ................................... .. ..........

Sample List - Excitation/Fluoresccnce Wavelength Measurtsment: TribIe 1 1 .....................

SampI t. List - Identifyins Daylight Fluorescent Materials: Tsble 12 ...............................

Bluc.\+.ooI Standards Fading Monitor for Sunlight Exposure: Table 13 ............................

Factors for Interference Filters: Table 14 ...............................................................

Monochromatic Excitation of Fluorescent Paints: Table 15 ............................. .... .......

Et'fccriveness of UV Filtcr Against Paint Colour Friding: Table 16 .................................

. xii .

List of Figures

hIac:\ciarn Lirnits: Figures 1 . 3 ...........................................................................

........................................ Fl~imsc'c'nt Mat~rials: Figures 4 - 6 ... .......

..................................... ..................... Fluorescent Brightencrs: Figure 7 (a ) - ( i ) ...

..................................... Fluorcsccnt Dye's Excitation-Emission 3D Spectrum: Figure S

...................... ............................................ CoIuur Dirigrams (a) - (d): Figure 9 ...

..................................... ...................... Natural Colour System: Figures 10 - 13 ...

Ost\vrild Colour Systern: Figures 14 - 18 ................................................................

..................................... ...................... blunscll Color System: Figures 19 - 2 1 ....

............................................. Colour Specification with Tristirnulus Values: Figure 22

................... ........................................ Chromaricity Diagrarns: Figures 33 - 3 1 ....

......................................................... Pouer Spsctra of Illurninrints: Figures 32 - 36

.................... ........ CIE Colour Sprice - CIE L*u*v3 and CIE L*a*b*: Figures 37 - 30 ..

XIsrrimt.rism. Figure 4 1 ........................... .. ... ... ................................................

....................... .. ISTM form 3B: Figure 42 .... ..............................

Introduction

I>:i>-lighi r l i i i ~ r c ~ ~ c n t pigments tluuresce in r eqmnsc tc) both visible and ultra\.iolrt radiation. T h e lisht

C ~ I I I I I L ' ~ h>, the pilmt'nt. o r t1ui)rt'sccnc.c. combines tvith the light retlected o n the surtiice ot'tfic pigment

partic.1~. Ctmscqliently, a n extraordinarily intense lisht is obssrved o n the pigment surface. and the pigment

gIon5 in da'-Iighr. T h e use u f t h é brisht (saturated) coliwrs c)iciayIight tluurescenr pisment5 starroi in

uci~crtising. but the applications soon expanded into rnriny other fiefds and matrrials. Daylight tluorescent

i o l ~ ) u r b rire tuund in everyday items. safety equiprnsnt and sarments. a s uz l l a s u o r k s o f art

( \ ' cuk-h .K. \V. Pi.qnimr Hcrncfbook \m. 1. 1973 1.

Dayligfit tluorescent pigments have bcrn on the market for mtiny decades and many everyday item5 rire

iolc)urc.d with daylighr t luwcscent pigments. Evans. colour scicntist. tvrote in 1072 that the phenornenon of

t1uorc.x-cncc hrid ' -gro~ving industrial and artistic importance" (Evans.R.iM. 1972). In the field of modern

art. Jriylight tluorescent pigment'; have played a signi ticrint role by rittracring v ieuers ' attenrion ivith t h a r

dazzlins optical proptxrics. these xt is t ic products o f daylight fluorescence aged. they srcirted to attrrtct

lhc attention o f conservators.

D~iylight tluorc.scent pigments a r e relativdy ne\v materirils: thercfcm. thry are potentirilly usetÜl for man?

applications. but at the srirnc time. \ve are not sure a s to how these marerials u i l i age a n d deterionite. This is

cspccirtlly truc in the conservation ofdaylight tluorescent items. whrther o r not t h q arc: intsndsd to be

rirtistic, \vhen the co lour is a n important aspect o f the objsct.

This rcscrircli i s dcdtcritcd to the basic study and the basic behaviour charric~erisaticin of driylight tluorescent

pigmcnts. In order tr) understand daylisht fluorescent pigments scientifically. it is nccessary to reviar. the

Irrcrriture in rclated f ields. First o f a l l . colour has to bi' understood scientifically. Second. the rnechrinism of

[tic phcnomcnon tlucirescençe has to be claritled. Third. the scientitic methods r o dcscribe and detect

colours and il uorcsccncc are invcstiyred. Finally. cxprrirnctnts hrivt: been conducted on dtiylight

t luorc~cei~t pigments usin2 the knowledgc acquirsd rhrougli rhc study mentiuned abovc.

Through csperirnentati~)n. i t \\.ris t;)und that spècrrophorc,rrictiry is ri ver? ctÏtxtive merhod to characrerise

and rccurcl the colours ~ Ï d r i y l i g h t tluorescenr pismcnts. T h e ctsperiments also provzd ihc effectt\.enr.~s of'

CI' t?lici-5 i n prcienring the detcriorstron of'ii)ic)urs in dri'light tlur)resct.nt pigments. .Mm. i t wris re~.zalr.d

rhiir ihc ct)lour changc rare oidaylight rluorrsient pigmenrs Ji t'fcrs depènding o n the srape of derr r i~~ra t ion

and on the thiskness ot' the pi2menrt.d I q e r . Above all, the data of the expzriments cleariy indicated the

markctdly poor l i~htflrstness of driylight fluorescent pigments cornpared to non-fluorescent rinist p i s p e n u .

Finrilly. i t \vas discovered chat the optical propenirs of d q l i g h t fluorescent pigments can b r tvell-

charactcriscd by analysing the rssults obtrii ned rhrough t\vo Ji f i r e n t types of spectrophotomerry and by

obscrving under UV light.

2. Tlieory and History of Dayliglit Fluorescent Pigments

2. 1. Theory of Daylight Fluorescent Pigments

2, 1. 1. \\lord Definitions in Bricf

'I'hc rcader 01' this thcsis rnay not bc farnilirir \vith ~vcmis used hsrt.. Some rrrrns have unique delinitions

rirnong conservarion profcssionals. Also, thcrr rire sumt: *or& that are interchangeable o r confusing

depcnding on the context. In order to a w i d rnisundcrstrinding. srme words rire defined spt.cificall>, for this

thchis. Thc rcadrrs a re encourrtged to r e k r to this section and tc) [fit. "Glossriry."

B~I?-!I ,~J/II is a type o f illum~nrition source thrit rcscrnbIcs indirect sunlight on ri bunny day. T h c componcnrs

ot'dii! Iight disrribute rarher cvcnly. ripprosirncitely bcti~,cen 3SO nm and 700 nm. crmsisting of ultraviolet

Iigh! and 1 tsiblc 11ght. F i t t o r c s ~ . ~ t ~ r mt'ans bcing cripribic ot'cmitting tluorcsccncs. Fltiorcscrticc~ is a kind o f

radiation ( o r light) emittcd when ri substrincs i'; cj.rcircd (stirnulated) by rin excitation radiation (o r light).

C'onvrntionally. bath daylisht tluorescent materiil and $on-in-the-dark types of rnriterial are called

tluoresscnt matcrials. but the Iritrer is phosphorcsc~'nt in ri bcientifjc detinirion. The tcrms lurnincscent.

phosphcircsccnt and tluorcscent are oftcn confused. .A Luminescent pigrneni crin be t luorrsïrnt o r

pht)qhorcsccnt. .A p/tospltorc.rce~ii pigment emits ~ v e a k light over a long period of timè afirr being sxposed

to the escitation radiation. and i t m a i glow in the dark. The prolonged light ernission from a

phosphorescent substance is crillsd cr/rergloii., .Aflrrorc.scCtrf pigment emits light as Ions as it is esposrd to

cscirrttion rridist ion. Dayli.qlit f l r ~ o r c s ~ ~ ~ ~ i pigr~rerirs. ri caregory o f tluorzscenr pigment. cire extraordinriril~,

brishr and arc intcnscly coloured under daylight. .A pigrrt~~lrr is used in the forrn ot' solid particles to ridd ri

colour t o ti mriteriril. A is uscd in the form of a solution to cidd colour to a material. Coiottr

Irl~w\lcr-c, t trerir I> ;in mcilyical mcrhod to specit). and dcscrrbc. colour scicntitkritly. In colour merisurement.

colcwr 15 defincd c i thr r by thc rctlcctrince curve ris a tuncriori oI'\r.rivt.lengrh in the visible resion o r by

tri~tirnulus values. Tr is t~mulus values arc the ratio among threc primciry colours. It is assumcd thar the

-, - 3 -

2. 1. 3. Daylight Fluorescent Pigments ris a hlaterial

Dziyligtit Fluorcscent Pigments. Overview: Clow Mïtliout Natter!

Dciylishr tluorescsnt p ipnents cire distinguishrd t iom other types of pigments by their outstanding

brighrncss. their e x t r e r n e l intense wlour . the hue of th& tluurescence. their ribility tu t luorescr under a

ccrtriin type of illumination I but not in the drirkl. and thzir trrinsprirency. Thesr: characreristics o f driylight

t1uc)rcscent pirrnents art. observcd in ci brighr place such ris by thr: tvinduw during driytimr o r under a

tluc-rrcscènt Icirnp thrit is comrnonly used in ri household. T h e s s pigments can be distinguishsti by msans of

coliirirneir> cbr spectrophorometry. especirill>, \ \ h m the pigments hrit-e no[ yet been exposed to

cnvironmentri1 stress and rhsy cire still Ïrcsh.

Firsi of ail. the colours of driylight tluorrscent pigments rire very sriturritcd. Saturarrd means vivid. bright ur

strong whèn i t d s x r i b c s colour. .A daylight tluorescent pigment has its o\vn colour. In o the r words. a

dliylight tluorescrnt pigment rstlscts light rit certain wavslrngths seleçtivdy. S o it has a colour even when

i t 1s nor crnirting tluorsscencc. r.-\~oston.G..A. 1987. pp.37-40) (Voedisch.R.W. Pigtttertr Hcrrd&ooX- r.. 1.

1973).

Second. daylight l l u ~ r c s c e n t pigments rippsar to be unusurilly bright in daylight o r under houschold

tluoresccnt tixrurcs cornpareci tc, non-tluorrscent pigments, Some driylight tluorcsccnt pigments _clou. under

\f'ti;it ol'rt.11 h;lppcnh to dri>,liglir tlur~rcscc.nt pigrlient is rhat the pigmrnt's o\vn colour (ret l rctsd colour) and

tfw colt 111r 01' tht: p i ~ m c n i ' s tlu~irr.sc.cnce are sirnilar. On thc retlcctrincc spectrum. the maximum reflzctancr

and rlic doniinrint perik ot' the tliicircxcncc appcar in the samc u*avelrngth region. Thus. rht: light rctlected

o n thc surface of the pisment rinJ the Iight eniitred (ib t1uc)rescencc combine to ïorm ri highsr perik on rht:

rctlcctanie curve. A s a result. an extremely inrensr colour is perceived. (Agoston,G.A. 1957. pp .3740)

f \'ot.disch.K.W. Piqnietzr Hn~r t fhook i.. 1. 1973 ).

. - 1 hird. anothcr unique propert! d driylight fluc~rc'scenr pigment is trrtnsprirency. Thcy Iack opricity; in othsr

\\or&. they h:ivc Icbs hiding p o u c r c..umpart.d t o mobr non-tluorescent pigments d u s ro the clear materials

th:it art. uwd a s the sotid carrier o f thest: tlucmscent pigmentb. (E1lis.XI.H.. e t al. ( 1) 1999)

( ~IrirrinJi1I.SI.G. L9SS) i \'oedixh.R.\i'. Pigirrcvir Hii~icfbook i . 1. 1973).

ii't1t.n a drtylight fluorescent pigment o n a painting is illuminrited. a ponion o f the l i ~ h t prisses through the

pi2rnc.ntr.d layer. is retlected by rhc substrritr. and cornes brick through the priint Iayer and unites with the

lighr thri1 comes fiom rhc paint surfrice. ThcrerOrr. the unusually bright appearance of ti daylight fluorescent

pigment is due 1 0 the combined et'fect o f the light rstlscted o n the pigment surface. its tluorescence and rhe

light rrtlected by the substrrtte. ri\ d q l i g h t tluorescenr pigmenr appears purer and brighter ~ v h e n it is priinted

o n a uhitr surface rathsr chan o n a dark coloured surface. Ir is true. thoush. that non-fluorescent pigments.

espccially Iake pisrncnts ' prscipirared o n barium sulphtite tBsS04). also transmit light to some extent.

cEllih.Ll.1-1.. et al. ( 1 ) 1999) tGerrcns.R.J.. e t al. 1966. p.96) (l'oc.disch.R.iV. P i p t e r u f/mdbook 1.. 1. 1973).

' 1-rikc pisment is ri ca tqc i ry d non-fluorescent pigment. It is made by dyeing incrt white particlcs. Arnong tlic tvhitl: matcririls li)r dyc crirriers. rherc arc barium sulphatt. and rilumina. Bririum sulphate is also called pcrrnancnt \thire. blanc tixc o r barites cGettens.R.J.. et al. 1966. p.96) (Colorer Irrde-r 3rd ed. 1982. pp.6-9).

T h e maximum spectral ret1ectanc.e o f daylighr tluorrscent pigment c a n be as high ris 300 %. (Drsig~iirr.p

i i . ~ r l l Dl~j-Glo Color. 199s. p. I 1 J. if the dyes in the pigment are selected appropriritely ! (Streite1.S.G. 1995.

pp.602-603 J. This esplains ~ v h y ciri) light tlu~wcscent pigments rippear s o bright thrit they arc: said ro yloiv:

t l i c ' ~ rire riirually emittinz light. The ret1ec.tanc.e o f an idcal \\'hite surface is 100 !'; through the ivrii.elengths

in the visible range (Agoston.G..C\. 19S7. pp.79. 211). and the reril materials ussd ris white refsrence t'or

~pcctn)photornt ' try have 7 s - 9 9 << spectral retlècttincs depcnding on the substance (\!'yszecki,G.. et al.

1967. pp. 1SO-186). Non-tluoresccfnr. coloured materials are nor able to ach i sv s ri retlscrance that is highrr

than the idcal \vhite surface becriuse. by drtlnition. the idsal \vhits surface retlects al1 light chat it receivss.

Ir is possible for ri non-tluorrscznt. colourr'd surface to retlect alrnost all l i rh t rit certain \vrivelr=ngths. thus

richieving ncarly 100 CG rztlectancr' a1 its dominant \vrivelengh \vhilt= ribsorbins at othrr \\.aveIength

r eyons . but thc surfricc cannot rrtlscr mure fight than i t receivcs to have retlectrincc above 100 5. Any

matcriri1 that hris r~.tlc.crance above LOO % rctlectrince in sprctrophotornerry musc bt: emiiring light (Graph

66 in Appendix V I ) .

' Chalk. CaCO; (Gettsns.R.J.. et al. 1966). > - r i o 2 (Geitcns.R.J.. et al. 1966). ' Chinescivhite, Z n 0 (Gettrns.R.J.. er al. 1966). ' Permancnr white. BriSO, (Gettens.R.J.. e t al. 1966). O - I'itrin,,.~~ white l i v e s ri violet colour tluorcscence and zinc white g ives ri yt.llo\v Iluurescrnce under ultrri\iolei illuminatiun (I)ifr~rrCrl & UlrrniGder Phorogrcipliy. 1972. p.26). . - ïtiis is cxplained in the section "Quenchins. Scnsitisins. and Enhancing of Fluorcsccnce."

In ~peitr i~photomctry. the brightncss c)f'daylight tluorrsccnt pigments docs ncit nccsssarily exceed 100 5

c w n it ' t l ic: rc:tlcctancç is highcr [ h m 100 5 ar the dominant pcak. This is bccriusc rhc luminancc ior

Iigfitncss of thc spscimsn i b n~ ) t :il\vayb mc;Lsured at rhr: &)riiiriant perik u ~ a v e l e n ~ t h . Thc brtshtness. o r rhc

nictric Ii~litncss in tcrms r ) i the CIE 1976 (L'ii'b") coluur ~~r:ci t icri t ic>n.~ is calculritcd using ihr luminance

i'aitor \' / \', (Agostun.G..-\. I9S7. pp.240-2-14]. Onc \vay to obtain the luminance factor (Y / Y,) i s tu

cornparc the rctlecr<ince of the spccimrn and the rcferrncr t i r LI wavelcngth o f 457 nm (blue) thar is used tLr

p p s r uliitcncss measurcrnent (Spccrroqtird I I . .\kuuccrl. p.70) (T453c>m-S7- T.APP[ 19S7j. Siill. 3 daylight

tluc~rrhccnt pigment tcnds to havc much highrr brighrness thrin a non-tluorescent pigment with a s imi lx

hue and similar degresa of saturation ( Voedisch.R.W. Pignrcvir Hrmdbook il. 1 . 1973 3 .

The dominant pcak retlsctrince ncit only exceeds 100 5 but i r aise) tends to be sharp in the reflecranse

spectruni o f a dql ight tluorcscent pigment- indicatin2 the hish excitation purity of ' the coiour. This rnsclns

thitt the pcak stands on a narrow \va~.e lengh band. and thereiore. the colour is compvssd of a small \.ririet>

oi hues. Thus the colours o f da>-liglit tluorsszent pigments are pt'rcri vcd a s \ery saturated colours

c.-lgosion.G..-1. 19S7. pp.5S-61 ). .As rinc)thcr uay to visualizc the high sricurririon of driylight t luorsxsnt

cc~lours. une srudy rrverilcd that rhcse solours tend to be Iocated ncrir the spectrum locus on the CIE

chrimatisity diagrrim. escept for purple. pink and blue (\'cxdisch.R.W. Pigrrirrir Hc~~idbook i.. 1. 1973).

( Figurc 1 ).

Dityli~ht tlucirltscent colours gsnerally have high saturation and high metric lightness (briehtnsss) at the

same tinie. As ri result. these tluorrscent colours exist outside of the Mcrcrldmn litrrirs that d e t h e the rireri

\~ .herc non-tluorrscent colours distribute in a C-oioitr spcrce. Xot al1 cotours in a colour sprice crin bs

psrceived by the human cyc. and rhc perceptible samut is Iimited by the type of illuminant. thus crearing

the Macilciam Limits tbr the non-luminous objm coloitrs that are non-fluorescent colours. Due to lisht

absorption by the pigment and the colour spccrrum of the illuminant. must colour solids cannot include the

' Scs the ~ ~ d o n "Calculation for the CIE colour ~>stems."

.-\pplications of Daylight Fluurcscent Pigments

Dciylight tlu~wcscent pigments ;ire usrd for acivertisinz mediri including outdoor bannrrs. billboards.

pohrcrh. ;inci tliers. Thcy cire rilso uscd ti)r s a t t y rnrirkings on rrircrati and instruments. trat'tis s ism. o u t t i t ~

L)r conhrruction work. huntins and sports. The attraçtivr colours of daylight tluoresccnt pigments rire

fcivoured for containers of detergent. cosmetics and commodities. Therc are manu other kinds of

applicaticms that use driylight tluorcscent colwrs: for example. t q s . grscting cards. book çovers. sports

cquipmcrit. slorhing. trishiunclhlc xccssorics. and art mcdiri. < Dc*si.q~lit~,tj irirli Dar410 Color. 1998. pp. 1 1 -

1 S ) ( El l~~ .> l . l - i - . et al. ( 1 ) 1999) Malloy- 1997) (\'wdixh.R.LV. P i.qrrwir Hmdbouk \.- 1 - 1973).

in terrnh r)f rnrirerials. rhere arc m3ny that take advanrrigc c i i daylight tluorescrnt pisments to add ri spcciril

iolc~ur c1'12c.t ro the tïnril produits: moulded plcistics. fribriss made of polycthylrne or vinyl plriscic';. and

paper. In tcrms of media kir coliiration. driylight fluoresceni pigments rire applied ris ricrylic priints. tempera

priints, \\atcrculours. riirbrush liquids. spray paints. crayons. and marking pens. Daylizht tluorsscenr

printing inks rire rivailable for silkscrcen, lithography offset, letterpress. f l e s o p p h y and = vat'ure.

( Dcpsi,qtii~i.q irirlr D 0 ~ 4 l o Colot-. 199s. pp. 14- 1 S ) (Pinsrics Giyiriccr-irig. Sep 109 1. p. 19) (\loedisch.R.lf'.

Pr,qtrtcwr Hïu~rll>ook 1.. 1 . 1973 ).

Driylight tluoressent pigments rerriin high visibility in twilight when the colours of non-tluorsscent

pigments bccome tcio faint 11, bc \ istblc crisil!. For this rrcihon. dq l ighr Ruorcscent producrs rire

particuiririy useh l as salèty signs and mrirkings used t'or trrit'tic. transportarion and other outdoor operaiions

ihrit arc ccinductrd ar drium. at dusk. and in brid weather. For the srimr recison. drtyIifht fluorescent colours

;LW et'f;Lct~~.r t i ~ r c>utdoi)r ~idvcrtisements. (Co\vlinpsJ.S.. et al. 1959) (Dcsigt~i~ig iiirli Duy-Gio Color-. 199s.

pp. 15. 54) ( Voedisch.R.W. Pigrrictrr Hrrridbook 1.. 1 . 1973).

Causcs of Deterioration in Daylight Fluorescent Colorririts

Ulrrtivic?lc: lisht degradcs daylight fluorescent pigments and causes these pigments to fade. A thick tilrn

rippiicririm (75- 150 {Lm) with hish pigment volume concentration ( W C ) retards the detericiratiun o f

dciyli2ht tluoresccnt pigmsnrs. Treatmrlnts such as addition of U V absorbing agent to the medium (or

vt.hiclc. o f paint o r ink) and thick top-coaring ivirh UV absorbing agent o v r r the pigment layer also slow

cio\vn tilt. fading o f the pisment c o l w r e t f c r i v d y . (Srreite1.S.G. 1995. p.603) (Voedisch.R.\fr. Pi.glnerit

1 1c;tt i ' i rinorhcr hrizrird t o causc culour c h a n ~ c oi daylizht rluorcsctnt pigments. Thesc pigments arc

sc\c.rc.ly &-reriorrttrd if rhey rire cipplicd on ci surfacc that is constantly heatcd. T h e dyss in the daylight

tluoresc.t.nt pigments ma! xithstrind 176'C (350°F) for 5 to 30 minutes only ~ i t h a slipht colour

dt.tcriorririon. if they u e r e manufactured during the third q u m e r of the 20" century. The colour of the

dciylight tluorcscent pigments availabls rit the end of the 20lh century mriy withstrind heat up to 200°C

i 39?zFi. The resins in thc pigment soften o r mrlt at vriryiny temperatures bct\veen 70CC ( 15SCF) and 170'C

c33ScFj. dcpending o n the type o f the resin. The resins in the pigments. ci ther thermoplristic o r

thermosetring. may decompose below 200°C (392°F). but some resins in the pigments used as colorants for

plli.\ric products a rc d c s i p d t o \cithstand heat up to 3005C (57ZCF). (Ellis.kI.I-i., e t al. ( 1 ) 1999)

Daylizht fluorescent pigments have littlcl tendency to coalssct. o r agglomsr i te in the media, unless solvents

in the media attack the rcsin of the pigment. [ f i t is nectrssxy to mis dwl igh t t'luorescent pigments with

w o n 2 (ox~gena red ) so l~xnth . such as tolucne. ta f ~ r m an ;1erosol. o r \cith nitrocellufosc Iacquer. solvent

rcsistiint grrtdc pisments ma' bt. used. Daylight fluorescent pigmcnts rnay contain residual forrnaldchyde

f'ixirri tic nirinut:icturins procrss. \\'ben thcse pisments are ripplied in casr in coriting. the hrrnrildehydt:

r i i l i l irilihc: scprirririon in rht. casein medium. rtierdore. i t is nccessary to add a formaldrhyde scavenser such

as dicyandiamidr. f \roedisch.R.\\'. P<ytriertr fcrrlcfiook L.. 1. 1973).

3Iünufacture of Düylight Fluorescent Pigments

31ost driylight tluurcsctinr pigments rire dilute solutions of dyes in transparent resins thi t become hard

solids at roorn tcrnperiture. Dyes used for mriny daylight fluorescent pigments rire either xanthene type o r

riminonrtphrhalimide type d'es. Esrimples of tliese dyes are iisred in Table 3. T h e resin can be either

rhcrrnoplristic or tlicrmosettin_«. Thtxmoptastic resins gsnsrrilly produce brightcr coiours but thcrmosetting

rcsinb rcnd to bc more resistant to he31 and chernicals. Pigments based on thermosctting resins crin bc

nilscd ~vith a widc range of solvents owing to the stability of th<: resin. Colorants made of this type of

pigmcni tcnd 1 0 bc. more rcsistant t u Iriyring in srorage. The highcsi quality fluorescent pigments in artist

Thci-niopIristic rcsins u x d t i ~ r mobt driylight tluorescent pignients art: tririzinr-moditied su1phonamidt.s.

Thchc rcsins arc tormcd by coccmdcnsing ri tolucnc sulphonamide-formaldehydc wirh ri tririzinc such as

rnclmiinc o r benzogurinaminc. Rcsins in this sritegor) rire so hard and friable rit room temperature thrir thcl

arc criIlcd -'organic giass." (Vc)cdisch.R.W. Pignwir t l tr~iclbook iV. 1. 1973. p.S94) but t h e sotien rit highctr

renipccirurris. Somc driyiight tluc~rescent pigments are briseci on solutions of dyes in rnodified giyceryl

phth:ilarc or t-inyl rcsins. The optimum dye zoncrntrdrion is usurilly below 5 52. and the brightness of the

pigrncnr diminishcs ribove this concentration becriuse of qusnching. Quenchins is explained in anothsr

scstirin o i this thclsi';. (Ellis.%l.tI., ct al. ( 1 ) 1999) (Vocdisch.R.W. Piyutetlr I i ~ m d b o o k 1.. 1 . 1973).

Somt: >ellow and orringr organic substances crin be ussd ris pignents without bcing dissolved in resins

bcsriux rfic>, hart. little quenching. Escirnplrs of rhis catrgor?. arc. 2-hydrosy- 1 -naphthrildehyde ;ind somc

orher a1d;izincs of riromritic rildchydcs. (Voedisch.R.\V. P i s m w r FIcuid6ook 1,. 1 . 1973).

Onc rncthd ot'producing tluorescent orange pigment is r o mis tht.rmoplastic rcsins rit an elevated

tcmpcrrirurt. unri[ the scilution becomes clear. then severai coluurs uf dyes art. added. Iieating is conrinurd

up ~o 1 7 S T t 352 'F). the solution is cooled to form ri solid. and finrilly the solid resin is ground using ri

micropulveriztlr or wet mill. The product is ri finely divided pigment powder. (Voedisch,R.W. Pig~rienr

Ilnridbook 1.. 1. 1973).

Anothcr mrthod of manufricturing daylight tluorescent pigments is to dyc carrier particles. For example. in

Bririhh fhtcnt 770SS9. fluorcsçent d i e s rire addcd to rin aqueous dispersion of polyricrylonitrile resin

acidilicd n.ith slacial rtcetic acid. The mixture is stirrcd for 2 hours r i t rotlm temperature. then filterzd.

uxhcd. and air drisd. Thc average prirticle dirimeter is 0.25 Mm for thc rcsin betortl mixing tvidi dyes and

127 um t;x the pisment a n c r atr Jrying. (\'cwîisch.R.W. Pr~lrictrr Haricibook 1.. 1 . 1973). The major

mrinufxrurcrs o t'dri~,!ight !luurcsccnt ptgrncnrs arc listcd in T d d e 4.

Csiuscs o f Fluorcsccnce

Therc arc nvo factor5 that m a k suhsrtlnces tluorcsce: the rnldccular structure and the spectral composition

ot'ttie illurninatio~. The molecular structure hris a great int1ut.n~-e o n the substancr's ribilitj* to tluoresct..

3Iobt tlucmsccnt dycs contain an anthracene ring system that have ft electron contributins groups in the

places 01.9- and 10- carbons. h l m y driylight fluorescent pigments are bascd on xanthene type o r

aminonaphthalimidr type dyes. thrit conven both ultraviolet light and shon tvavclength visible light (btue

and grcen) into visible tluurescence. The rclationship bet~vren molecular structure and tluorescence is

Ïurthcr discusscd in the section "hlechanisrn of Fluorescence." (Vocdisch.R.lV. Pigrricrrr I-lcir~riiwoA- 1.. 1 .

1973).

The c o l w r spcctrum of the illumination 1s another factor tc, cimtributt. to tluorescence. A non-tluorescent

c)rmge pigment and a daylighr t l uo rwxnt orange pigment m;iy have similar hues in daylighr. except that

rhc t1ur)rescmr une is brighrsr. Undcr bluc- or green-coloured illuminrition. however. the non-fluorescent

orringc \ciIl appcrir unsaturateci ') \vhile the tluurescent pigment \vil/ glow wirh an orange hue. This is

bccausc rhe non-tluorescent orange pisment does not retlecr orange light under blue or green illumination

u.hcrcas the fluorescent orangc pigment convens blue and green light into orange light. By the same

principle. the _slo\r. of dayli_rht tluorescent pigments are especicilly pronounçed in the twilight of d a m and

dubl;, Lvhrn thc colours of the surroundin? environment nrr nor so srrturated as they arc durin2 daytime.

( l'oc.disch,R.W. P i g ~ t ~ m r HCIII~LUOX. 1.. 1. 1973).

" \'t>edish dcscr~bcs r his colour as black (Vucdisch.R. W. Pig~rwrir l I ( ~ ~ i < I D o o k 1.. 1. 1973).

[IsyIigIit tluorcsccnt pigment3 lack opricity due to the trcinspclrcncy of resins used ris the carrier of dyes.

c ~~l ; i r t indi l l .~I .G. 19SS) therclixe. thesr pigments Irick the clliility to obscure the substrrites. This means thrit

the rippc.;ir;incr: ot 'a daylight f l u~ rcscen t coritlng is greritlj. ~ i f c c t e d by its substraw. The primary purpose of

ciriylight tiu~ircsccnt pigment is h r decorrition r)r for identific'cltion, and this is sicctimplished by the bright

ripperirrtnct. ut' the pigment. For this rerison. a Jaylight tluorescent pisment must bc applied o \ x r ri \vhite

urt'ricc. .-\ n hitc surt'rise retlccts \vhitr lizht to add t o the brigh1nes3 of the daylight tluorescent pigment

n.irhour tnrcriering \virh the hue of the pigment. In ccintrrisr. (I dark substrriie does nat reflrct lighr ris much

but wÏll ribsorb the l i ~ h t thrit is transmirted through the pigmentrd layrr, and the unique brightness of the

drij~lighr rluurescent pigment will be losr. If the srime subsrrate is used. the brightness of ri cosiring ~ t i t h

cfrrylight t1uc)resccnt pismenrs 1s proportional both to the t h i i h e s s of the tjlrn and to the pizmenr volume

c.onc.enrr;iri~)n (PL'C) of thc film. (Vc>sdisch.R. W. Pi.yr~lerir H~11ici6ook i v . 3 . 1973).

-. 1 he lighr rccrived o n a coloured surface is partiallx retlected and panially absorbed. Fluorescent pigments

rire caprihlc o t ' a b s o r b i n ~ lighr at prirticulrir wrivelen~ths (or frrquencies) and re-emitting the energy of

ahsorhed l i ~ h t at longer \i .~t\.elenghs (lo\ver frsquencics). ';rirural producrs such a s quinine and vririous

mincrrils tluc)rescr in response to u1tr;lviolet radiation. hlrinj synrhstic compounds. both i no ryn ic and

ursrinic, exhibit vivid colours under intense ultraviolet lisht. The saturri~cd colours of these materials occur

ris ri conhequrnce o f the phenomenon. tluorescence. (Voedisih.R.W. Pi~n ienr Hrrridhook 1.. 1 . 1973).

1-icrc. rhc rcadcrs rire reminded thrit rhr \vavelength and the r i e q u e n q of light rire reciprocril. a s this is

cxplriincd in the section "Light is rin Electromriyxric Phenornena" \\pith the equrition C = if2 . C is a

constant number, i~rcprescnts the frcquency of lighr. and 2 rtpresents the wavelength of light.

(hI;irtindi!l.3l.G. 198s ) (Skimg.D.A.. et al. 1995. pp. 1 1s. 130) (Voedisch,R.W. Pigrricrir H~ctrcluook i-. I .

1973).

13rior to thc cnergy absorption. alrnost al1 molecuiss exist in their lowest e n e r g clcctroriic sture thrit is

c ~ l l c d thc ,yt .o~mf SICIIL'. The absorption of radiation is a ver? quick process ( within 10-l5 seconds or less, in

the ultra^ 1olc.r and \.ibible rcgion r ~ f t h c clcctromrigneti specfrum. When a rnuleculr ribsorbs radiation

cnerry. elcctnms are promotcd tu higher e n e r g orbitrils. thus bringins up the rnolrcule ro an excitecl

r c~lc~~rt-oriir-) sturcD. A moleculc: crin have many dit'l'c.rsnt c.lcc.~t-o~iic-clll~ c - r c i rd r ta t rs (or electronic srrites).

2nd rsifi rlcctronically cscitcd ';frite ha5 ri nurnher of differcnt i.ibrcrriot~cdl~ crcired srores (iibrcrrioricrl

r ~ i o d ~ , s ~ . The lo\vt.sr e x c ~ t e d ~ ' I c c ~ r ~ n i c statt: is crilled th t f i r s r c ~ c t r ~ d s t c ~ r ~ . (Sriunders.D. 1995) (Skoog.D.A..

ct al. 1 W S . p.350-360) ( \'o<sdisch.R.\\'. PipnlL.rit Hmidlmoh 1.. 1. 1973).

Orlie ri rtioleculs is r.sciteii. the vibrational enrrgy is soon lost as heat by collision with neishbouring

niolcculcs and the molecule gocs do\vn to a 1otr.t.r vibrational l a r d u-ithin the stirnt. excited electronic srare.

This ib a nonradiritive process cailed iqibt-arioticri relr~vruiotr. The lifetime o f vibrationally excited states is

IOO short t;)r photocmission to occur. After rcaching the lon.c:st vibracionri1 lrvel in the first (the lowest)

~ \ i i ~ c d r.lc.c.tronic stritc. that is more stable thrin vibrritionally sxcited states, the molrculs loses the rest o f

irs energy eirhcr throush radiative o r nonradiati\.s procssscs. and returns to the ground energy state.

r Skoog.D.:I.. et 31. 199s. p.358) ( Vordisch.R.\V. P ~ S I J I ~ I Hind6ook 1.. 1. 1973).

~ 1 ~ ~ l c . c u l c s ut'sornr. subs tanc t .~ It,c;c rhelr enerpy by relrrisin_r photons rtfit.r rsrichin;! the lowest vibrational

Ic.\.c.f in the tirst cscitcci stritc'. T h h photon flan. is crilled /wri~texcet lcc . If the s p n o f the rlccrrons is not

chmgcd 'O \vhen the rndt.culc ribsorbs energy. rhr emission tiorn the molecuit. occurs immediritrly a s

/Itr~t.c~.\r.c'/ic.c'. 11. thc spin o i the r.Isctrons is chringrd " duc r i ) energy absorption. the elcctrons m q undergo

ri t'urthcr process to rcturn tc, the ground =tate and rc-rmit energy ove r 311 extendcd period of t ims as

~ > ~ ~ u s ~ I / ~ ~ I - ~ ~ ~ c . c ~ I I c c . (Skoog.D..A.. e t al. 199s. pp.356-300) (Voedisch.R.W. Piglrictir Htitid6ooX- 1.. 1 . 1973).

T h e IiKetime 01' luminescent emission depends o n the process that the electrons g o through. thersfore. the

cmission period of Iuminrscence dt-pcnds o n the type of substance. The emission period o f an organic

pt io~phorcscent material i-; s h o n but thc lifctirne o f tluorescrnce is rvsn shonrr : fluorescence emission

continues for only IO-'' to 10.' scccmds \vherecis orglinic phosphorescent substances have emission lifetirne,

or' IO-' [O several seconds. Phosphorrscent ernission tiom inorgrinic substances crin br longer and

wrnerimes may crmrinue a s Ion2 a s 12 hours. Organic phosphorcscrnt materials rire used for tagging

\.;rrious ircms. for example. in the post office service. Inorganic phosphorescent substances rire sold a s

gloit-in-the-dark pigments. Long phosphorcsccncc emission is richirved by inorglinic polycrystalline

pigmcntb thar arc cc)nipris<--d of the sulphides o r silicritcs of zinc (Zn). cadmium (Cd). bririum (Ba ) o r

I iJ Elcctrons 01- rnost substrinccs art- in the s i ~ r g l ~ r srnre both rit the ground state and in the exciteci state î \'ocJisch.R.\'. Pi.qr~rcrrr H~~trc lbook 1.. 1. 1973). 1 i Elcctro~i spi11 rc.\.crsal from sirzgler sture to rriplrr srtirr. T h e electron must change its spin to singlet s tate asriin t ~ f h c n i t socs back to the ground state (Voedisch.R.W. P i p ~ i m r Hctnd6ook iy. 1 . 1973).

Thc cnrrrgy of an c l c ~ t r o r n a g n c t i ~ radiation including ~ i s i b l e Iight is functional to ils frequency: E = / I t*.

1 ICI-c. E 13 the rimount (quantum) ~ 1 1 ' radr:iiion cncrgy. I I is P l ~ l k ' s corl.mirir and t' is the f r r q u e n q or' rhr

radiaticin. In many cr?ssh. the crnission oi lurnincscence occurs rit longer \s-rivclenghs (lo\ver f iequen~'ies)

tliriri c~citritii)n radiation becauriri the rimount of energy re-emittrd is smrilfer than the amuunt o f znergy

ribsurbcd. This phenornrnon is kno~vn ris the Stokes lait-. o r the Stokes di$ , and this is d u r to the initial

enersy ICM through ncmradiativr rrlcisrition thrit precedes the onset of phocoemission. Although the Stokes

shi t't occurs in mc\st f1uort"jc~'nt mritcrials. thcrc rire substances thrii emit tluoresccncc rit the \vri\.slengths or'

the excitation radiritionh. Fluuresccnce from such rt type o f substance is calleci r e s o ~ ~ c ~ ~ ~ c e ~ ~ ~ o r e s c - t ~ ~ ~ c e or

t-c~~orrritlc-~~ rtrriiclriori. (hIartindill.bI.G. 198s) (Skoos~.D.A.. rit al. 199s. pp.356) (Voedisch.R.W. Pigrrrrr~r

/f(c~itlhooX. i.. 1 . 1973). ( Figure 4 1.

There is ri relationship bt.t\\wn tluorescence cictiviry and mrileculrir structure. Light is absorbsd mrtinIy dur

t o the prexnct . 01' nonbonding rlcctrcins. or non-Iocal~srd mobile electrons. Examples o f nonbonding

elcctrons are tuund in the oxygen arum in aldchydes. Non-1osrilist.d clectrons cire 7: tlectrons that. is-hen

nian. ssist in one rnolscule. rcduccs the r'nergy required t'or excitation of the molrculr. As a rrsulr. Ions

\vrivt.lc.ngth (low frequency and low cnergy) tridirition such as visible light brcomes able to excite the

molccul~.. Anmiritic substances ivith syrnmetriçal conjugated bond systems '' have strong absorption. yield

intense c<ilc~urs. and sometirnes tluoresce. ( Vocdisch.R.W. Pi~rrierir Hurz~luook 1.. 1 . 1973). Most

unsubstituted riromritic hydrocarbons svith fused ring structures. such as quinoline. isoquinoline and indole.

1' Crirotenoids have extensive conjugated bonds that absorb enrrgy to yield sriruratcd non-tluorcscent colours bu[ rhzy d o ncit have riromatic r i n p , therzfore, they do not fluoresce (Voedisch.R.W. Pigtticrir f /<lri</lIcloX- 1.. 1 . 1973).

Suh~ritutiim~ on aromatlc rings riftZct rhe tluorcscence. Ortlio- and para- substitutions tend t o enhance

tluorcsicn~e but meta- mcilccular groups oïten rtiduct: tluarescencc. rc elcctron contributing groups. such ri-,

Cl i. O. S. Sf 1 and S . crtiate the opporrunity for t1uorescenc.c ro occur. but clcctron ;icc'ep[in~ Sroups. buch

1 ; s h l . tend to decrease the 1ikelihr)od of the mc)leculc to fluorescc or rend to \s.eaken the

tlui)rcsc.rnce. 1Streite1.S.G. 1995. pp.593-593 ) i Voedisch.R.\ir. P;,~rrlerlr f /mci /~ook 1.. 1. 1973).

Qucnching. Scnsitising, and Enhuncing of Fluoresccncc

Q 1 1 ~ ~ ~ 1 ~ 1 1 1 ' ts ;1 consumprion o f tluores~encc through intermld~.cuIar processes: for esrimple. tluorcstxnce

mriy bc <ibborbed by c~ther rnolculc~. the energ! 01' the escitcd rnolccule may be lost in molecular

iollision3. or tlic cncfrgy ma? be tr:in&xrt.d ri, ;i molecule ot'mother substrince w~irh a ccmjugrited bond

h!.srcrn. The optrmum cuncentrarim d a tluoressent dye solurion tends w bc lotv becriuse quenching

dcsrc.asc3 rhc efticiency of tluorcsccnce in a rhick solution. 3Ioleculrir collisions and uther nonr3diririvc

Jt.;icriv:irtcws arc' reduccd as the tcmpcr;Iturc is Ioucrrld. and arc' mostly inhibitcd \vhen rhe solurion of-

tli)rt.scenr substance is irozcn ro bccome solid. Thus. ri tluorescent substance caprursd in ri solid marris. as

in ri p ipent . sains rhe ability ro tluorcsct: more inrcnsel)*. This immobilizrition of rnoleculss in a solid

rnatris also cnhrinccs the lightfristness of the dye colour. (Streitel.S.G. 1995. p.596) (,Vocdisch,R.W.

In contrabt to quenching. ri fluurcscent dye molecule can piçk up excitation cncrgy from another substrincc..

2nd h:i\.c c.nh:inccd I'luorescencr. intensity. A substance thrit donates cncrsy 10 ri tluc>rcscenf substance is

ciil lcd ct . s c1 r~s r~r :~~r . (Strc.itc1.S.G. 1995. p.595)).

1: f:luor~ne (F). brominc (Br) . and iodine ( 1 ) (Srrrite1.S.G. 1995. pp.592-593).

Onc t lu ,~rcxxnt d y c can enhancc the coltwr ol 'anothcr tfucmscent dyc. Alberta l'cllc,\v d y r ( a yc.llo\v

t lut)r~>~-r .nt dyc) and Khodaminc f'3B ciyc ( a purplish rcü tlucmsccnt 4 c ) crin bc ricicicd ro Rhodaminc F5G

dyt. ( a pinkish orrings tluc~rcsccnr dj*c). t o Ïtirm a pigmrnt N ith a briglit orange colour and a grcriter

tluc,rcs~cncc pcak hsight.14 In this casc'. thc .-Ilberta Yrllo\v dye ( w l l o w ) absurbs [lie blue-viulct pr~rtion 01'

the cniis5ion ticjrn the Rhodaminc F5G dyc (pinkish orange) ivhilc cxçiting the RticJcirnins FIG d>,e

c piriAish t)rringr) \\rith its yc.llcnv f iit)rcssr.ncc. and thc R h d a m i n r F3B dyc: ( purplish r sd ) displrices thc

peak of. the Rhodaminr F5G dye (pinkish orange) toward rhr longer wrivelength region (red). T h e

r 7 u o r c ~ i t . n ~ ~ o f borh the .Albcrt:i ~ ' c l l i w duc (>ello\v) and the Rhodarnine E3B dye (purpiish r e d ) combine

thc ! 1 ~ 1 ) r ~ ' ~ * c n c t ' of' the Rhodaminr: F5G dyt: ipinkish orange,. producing a higher dominant psrik.

i StrcitcI.S.G. 1995. p.599).

2. 1. 3. Fluorescent Brigliteners

Flucircscent brightcncrs rire not regardcd ris daylight tluorcscr'nt pigments becriusc rhey rire no[ used as

ctilorants in gensrril trrms: ho\vcver. it is imponant tu r r a l i x that tluorcsccnt brightenc-rs function in the

hame \va!. thal daylight tluoresccnr pigments do. On the one hand. scientific information abou t driylisht

tluort.scenr pigments is no1 erisily riviiilriblc.. O n the othsr hand. scientitïc information about Iluc~rescent

briglitzncrs is r ibundmt and is more crisil). availabls. Paying attention to tluorsscsnt brightcnrrs 1s one \vay

rl! undcr'tlind daylighr t1uc)resccnt pigments.

Zolltngcr ~'stirnrired that the total prciduction ot'fiuc)rescenr bristiteners in 198-2 \vas 33 000 tonnes. .About

51YX oi rhcm ivcrt. uscd for dercrpcnts, about 33% for papcr. 15% for textiles and 3% fbr pListics.

( k1urray.S.G. 1996. p. 1 S4 1.

~ ' I~ luor t .~ icn t brightencr" I Coloar- I r i t l c , . ~ 3rd cd. 19S2. pp2-5) is ri pecufirir cI:rss of synthetic dyes thrit are

col t~ur l t .~s o r tverikly col( ~ u r d orgrtnic compounds. and art. tluorescent. (Singh.N. 1999). Thest: dyzs hri\.r

v;iricius names: "upticril brighteners." i Schuun;er.M.J.. et al. 1989) (Singh.N. 1999) (Wintgrn-M. 1987)

" t l ~ o r c ~ ~ r . n t brightcning a i p m ( FB:l>)." i hIurrr1y.S.G. 1996. p. 1 S.)) "optical brightening agents (OBAS)"

i kIurr:i~ .S.(;. 1996. p. 1 S-i ] ancf "t'luore~cent \vhitcning agents (E=N'.L\s)." ( McE1hone.H.J. 1994)

(h1urrriy.S.G. 1996. p. 16 1 ) (Singh.N. 1999). They function by increasing the apparent whiteness in hue and

brighrness ( rnetric luminance ). (Murrriy.S.G. 1996) (Singh.N. 1999).

Upon abscrbing u1trriviolt.t l i ~ h r . a tluorssccnt brightencrr emits visible light ciround the blue-violet region.

1' 16 Thc biuish t1uorescenc.e crinscls the ~e l lowish hue on a tvhitc surface. and makes the appearrincr of the

surfacc tvhitsr thrin it acturilly is. Fluorescent brighteners tluoresce both in daylight and under tluorescent

1:imps: thriretare. the? rire ripplit'd to hidc the comrnsrcicil products' natural. slightly yellowish tint thar

givcs rin old and dirty impression. Priprr and fribrics c m be dyrd u'ith tluorescmt brishteners during the

mrinut;icruring procsss. and laundry is dyed lvith the fluorescent brightenrir in the detergent during the

wcishing proccss. (h.1urray.S.G. 1996. pp. 181- 1S5). Sincr the invisibk portion of the daylight specuurn is

ionverrcd ro visible lighr. the energy o f pctrceived light increases and rhe brightness o f the material is

bigni ticanrly enhancrd. c Singh-N. 1999).

The inherent yellowness o f papcr pulps (even after bleaching) may made invisible by the use of either

tvhitc tillrr pi-rnents " o r ri trace amount '' of a blue-violet dye. but a much brighter white can bc achieved

by t1uorr.scent brightencrs. and this rcsults in a higher contrast for writing and printing on paper.

( iL1urray.S.G. 1996. pp. 1 S4- 185 ).

-

" 100-500 nrn (Murray.S.G. 1996. p.1S-l) (Singh.N. 1999). 1 0 - îliis is an e f i c t o f mising cornplimencary colours. 1 7 7-10:. Sor example (Murrriy,S.G. 1996. pp. 18-1). 1 k Crin bc lcss than 0.005 % t ~Murray.S.G. 1996. pp. 184).

'I'hc. rnc.iti:i~iism of ~~~~~~~~~encc for tluorcsccnr brightcnsr?; is similar to that for coluured tluorescrnt dyes

but ihc r ~ i ~ ~ l c i u l ~ s 01' t1uc)rescent brightcncrs ribsr~rb rhc cnergy of radiation rit shortrr \vrivelengths becriuhtt

the? rcquirc much mort. rncrgy tc) bc. cxcitcd. The tluorcscctn~c emission sprictrum cil\vays rrhidrs on h i ~ h r r

\i ,~iwli.righs than the absorption spectrum. therehre. tluorc-lscmx crin occur in the visible region ris ri result

~i t 'cscirr ir i~~n by iiltrriviolct Light. (Sin2h.N. 1999).

3lolcïular Structures of Fluorcscent Brighteners

Stilbcnc cumpounds (having one o r rwo stilbenr residues) consritute about 80% o f the total usase of

tluorcxcnt brightcncrs and paper brighrcners arc rilmost esilusivcly stilbene brised. This type of

tluorcsient brightcncr is chcmicrilly simitrir to rinionic direct dycs. Both of them have plrinrir o r lincar

molc.cu!c.s tivrh Iargc dc locdised n elecrron systrrns and one o r more sulphonic acid groups (-S03H).

I 31urray.S.G. 1996. pp. 1 S5- 186).

XIosr of brilbene type brightcners are based o n 4.4'-diriminosritbene-3.23-disuihponic acid (Figure 7. a). and

mriy be obrriinrd by ri chernical rraction that involves cyanuric chloride. (Fisure 7. b) follotved by

condcnsririon of the product (Figure 7. c ) tr.ith siiitrible cornpounds to inrroduce groups such ris amino.

alkylriniino. arylamino. hydroxy. alkosy. aryloxy etc. This sirries o f rerictions yiclds a molecult: rhat is

symmctricril. plrinrir. and tluorescenr (Figure 7. d). Asymmetricril moIecular structures bassd on 1.4'-

diarninostifbcne-2.2'-disulhponic acid (Figure 7. a ) crin be ustd as tluorescent brighteners, as well as rhose

brised on ?;!stems \virh tmx~ s t i lbme residucs to givc Irirzer mo!ecules with estcnded çonjugrition bonds

(Figure 7. el. (3lurrriy.S.G. 1996. pp 1 S5- 1 S 6 ) Thsre rire many other chernical types thrit are generritly

ripplicd r ~ ) textiles but not so otien to prtprr. Thcy are mainly coumarin derivritivcs (Figure 7. f ) . 1.2-

cthylenr drrrivatives (Figure 7. g). diarylpyrrizolines (Figure 7. h). and naphthdimides (Figure 7. i ) .

( blurray.S.Ci. 1996. pp. 1 S5- 1S6).

f - - lucw~~cn t brighrcners are also found in the fi,llo\ving crireyories: styryl drri vatives of benzene and

hiphcn! 1. pyrazofincs. bib (benzoslizul-?-y11 derivatives. cournririns, crirbostyrils. n:iphthrilimidcs.

x~l i i r r i ino Jcrivririves. and pyrenc derivutves. (XIcE1hone.H.J. 1994).

f-or tliit~rc.sient brighteners. tlie tluorescence efiiciency. or the q r r t r l i r u n i ?idd ( O, 1. is as important a s the

[ S b . u r I I I l b r i n TIie quantum yicld rs a mcuurt . of the nurnhcr of molecules thrit Ic)sc their

t.ncrs> t'rom thc tscirtxi strirc to the ground state by tluorescrnce and not by other means (vibrarional

rclaxrirr~ins etc) . IfaII sxcitsd rnc)lecules tluorescc. a, = 1.0. If only 50% of excited molecules tluoresce.

then O, = 0.5. Brside the strong influence frorn the substratc, eteçtron tsithdrriwing groups pressnt in the

chromciphore ( e . g -SO;H) mriy decreciss the tluorescence. giving ri s m d l e r 0,. ~vhereas zlectron donaring

groups IL'.^. -OH. -NI-1'. -0CI-I;) mciy insrtxtse 1 1 . .-IIso. elcctron dlinriting groups ma! increcise the

tvcltrt.lcngrhs a i tluorescence and ultraviolet light absorption (bathochromic shifr) and electron n-irhdratving

groups rnay decreastt rhrm (hypsuchrumic shiti). (Murrriy.S.G. 1996. pp. 1 Sb- 187) (Skoog.D.A.. r't al. 199s-

pp.-3GO-;6 1 ).

Applicliiion of Fluorcsccnt Brightencrs to Pliper

Tlic amount of tluorcsccnt brightencr 2nd the ripplicatron merhoci crin vary ris in the crise of dyes. The

arnc)unrs arc 2eneraIly Iow (O.?<;: ur Irss as active matcrial) for sufficient brightening. The \vhitr.nsss

p o s s i b l ~ tncrcrises up to a certain extcnt a s the fluorescenr brightener builds up. but then the whitzness

decrccixs duc ro the inherent colour 'O of the fluorescent b r i ~ h t r n e r . This is crilkd greeninz o r yrllowing.

1') Therc arc other ways to merisure the whiri-ness of pripcr. for example. the 'TAPPI Brightncss rncrisurcrncnt" thar rne;lsures the reflectançe o f priper under a monochromatic illuminririon rit 457 nm. o r \fisiblt: spcctroscopy that puts out the vrtiues ofei thrr the Hunrer Lrib. thc CIE L*a*b*. the Huntcr iihitencss. the Stensby Wtiitencss, o r the Ganz Whitcness (Prirkes.D. 1989). '0 Rcflectcd colour. or the colour that is caused by the visible light retlectrd by the molcculss of the tluorcsccnt brightencr.

2. 1.4. 1.lealth Issues of Daylight Fluorcsccnt hlatcrisls

l lost rnxcririls for the rnrinut'ricturc oi daylight fluorcsccnr pigment5 hri\.r luw or no tiixicity. and dalelight

tluorcscr.nt pigments rire considcred tu bc non-toxic (Strt.ire1.S.G. 1993. pp.603-606) (Voedisch.R.lkr.

I - > i , ~ ~ ! t ~ w r I/cirirll>oc~X- 1.. 1 . 1'173 J. Day 1 ight tluc)rt.sc.rnt pigments thrmselves are not liksly to pose signiticant

lierilth problems ro thcir end-usrrs under regulrir conditions. Still. sorns driylisht fluorescent dyrs and

p ipen t r ; are knotvn to have acute lethal effscts on anirnals used in large-quantity esposure tests of these

pigrncnts therrt'cire. it is \vise to avoid oral cmsumption of. or externa1 contact with. daylight tluorrscent

pigrncnts in a Iarze qurintit!,. Pcoplc \\.ith srnsrtivities rnay hri\x to bc riivarc of the residurtl rnatcririis. such

ris iurmri~dzhyde.~~ from the manufricturine processes. When hrindling dry pigment powder in a frictoty. the

use of ri tcntilation systrrn. rcspirator and ~ t h e r srifery equipmrnt is rscornmendsd. (Streits1.S-G. 1995.

pp.605-606) (Vcrttionr SIR[) (Vocdisch.R.W. Pigttlrttr Hmdbook v.3. 1973).

'1

, * Pulp su.\pcnsirin in \i*ritcr as ri raw material for paper. -- S i x is one of p a p a additives. 2 7 Tirrinium dioxidr: also hris violet tluorescrnce (1rlfrtrrrc-f CC Crlrrirr.iolcr Plioro,qrcr/l/t~.. 1972. p.26). : J Chalk has eirtier violer. yelloir.. rcd or bro\vn fluoresccncc depcnding on tlic product (Itlfr-rtrd CC Lrlrrtr i.iclc~ P /~orq4~nrp l i~~ . 1 972. p.26). 3 Calcium carbonate (CciC03) precoat on papa and linerboard has more optical brightener citiciency than c'la)' prccoar (The ~ y p c of' rhc optical brightrner is not rnentionsd) ( Wintgen,M. 19S7). '" Vocdisch.U.\V. P;+ynrcwr Ilr~ttdbook is.2. 1973- p. 147.

2. 1. 5. u'scs of Daulight Fluorcsccnt Colours

.-\ rt aiid Design

Driylighr tluorescrnt colours arc used not only by artists but also by industrial designers u,ho w w k with

pxkriyr. d e s i y . apprirel design or roy design. jus[ to nrimc (Drsi.q~iin.g ~ i t l r h j - G l u Color. 199s. pp. 14-

i S 1. Therc arc. \vorks of art thrit rire intsndsd IO bc vieued under black light although they have daylight

t1uorescr:ni pisrncnts as cumponcnrs. Black light is a popular illumination apparatus a m o n t bars for its

uniquc \,iolct-bluc-culuured light. Black light rtcturilly cmits ri substantial amount of ultra\.ioIer light d o n g

u.irh visible blur: light. I t may be rcgarded as ri wrong usage oidaylight tlucmsccnt pigments if the piece of

x r is intendcd for ripprecicition unly under ulrrriviolet light in a dark place. bui actually. it is not wrong at

d i . Th13 1s a parridox caused by the term ri~~~~li~ltrfluor~lsc~tlr. Usually. people rire only rtware of the visible

part ot'ciriylight. Hcnvever. ultrrivicilct lighr is also an important comportent o f daylizht. and many driylighi

t luorc~cent pigmcnts do tluorrscc. under ultraviolet light. (E1lis.M.H.. e t al. ( 1 ) 1999) (iMrirtindill.M.G.

I9SS ,.

Wallcrt (Wa1lert.A. 1986) rrportsd that many naturril red dyss tfuoresce in concenurited sulphuric acid by

rrcciving excitation radiarions ni th \vavelenghs rit o r above 100 nm. For this study. a specrropl~oronierel,~~-,

Kontron :\naIytical SFM 25 \\.ris used. This instrument had ri mobile excitation monochromator and ri

mtrbilc. ernission monochroniriror to scan bc~tli the excitation riidiation and tluorescsncr through the

n.;ivclcngth rrinpc o f 200-S00 nrn (Figure S ) . This study \vas nat about pure dyestuffs nor dyed textiles in

dr). conditions. thrrefim. thc w t t w r s o f [extilcs ui th thest. dysh crinnot be inferwd from the rrsults of

\i'rillcrr's study. Somc d>.c.s rire knou.n tc) change colour depending 1x1 pH o f the solution ~\ValIcrt.A. 19S6)

(Zol1inger.H. 1957). Nonstheless. i t is \vorth\vhilr to br a n a r c uf the dyss that are found to be daylight

Iluorcscent in acidic solutions. These dyes rire listed hzre ivirh rhe esperimentril excitation \vavelengths in

9 - pmmhrs i s . - ' Ked~vood dyes (escited rit 430 nm): brazilu.ood. sumac bvirh basic copper acetate (rnainly

uscd as ri yellow dyr:). and r rd sandril\vood. Madder-type rinthraquinones (415 nm): cornmon rnaddrr

(Kubia tinctcirurn). ~vi ld madder (Rubici peregrina), asperula odorata. and gaIium crucirita. Scale inssct dyes

(120 nm): kerrnes (Rooscn-Runge). kermes (Fliedsr) and Polish cochineal. (Wril1en.A. 19SG).

Scicncc and Tcchnology

Fluorcsccnt substances arc. \videly used in 3 vririety o f fields outsidc o f the fields o f art conservation and

tinc a m . Thr ripplicriticins o f tluoresccn[ pigmcnts in scicncr: and rechnolosy rire introduced in Appendis 1.

. - - ' The cscitiition \wvt.lengths ot 'a tluorescent dut: exist over ri broad rringe ot'continuous wvelengths rrithcr than a specitic wri\dength. (Wa1lert.A. 19S6).

7 9 . . History

2. 2. 1. tlistury of Lurninc~;ccnt Substances

'flic dtiys of Alchcmists

.-\n)unJ 1603, rilchcmist C'. Cascariolo c>bher\cJ phobphoresccnce i afterglwv) h m Lin inc>rganic matririal.

. - 1 he m;ttrrriril \vas nut natural but was niade in CLiscariolo's Idx~rritory by heriting ri Stone thrit contriin

bririuni sulpliatr (Ba.50: ) 8.vith coal. thus producin? bririum sulphidr (Bas ) . This is the tïrst recorded

17uorcscent material ubherved by man. This finding encourqed Cascririoio in his quest for a mcthod to

b>,nthesiw suld tiom baser materials that &nt- cifier exposure to the sun (Sol. gold).'"hc tsrm pliosplior

( light-bc1rr.r) wris crerired d t r r C:iscariolo's glowing siont.. crilIed Bolognri Stone. and this did not take long

because the stonc gensrarcd considtxrible interest rirnong people. Barium sulphide is clrissitied arnong the

alkaline erirth sulphide phosphim. some of which playcd important roles during World Wrir II. (By1er.W.H.

P i y t ~ ~ . r ~ r Hi~ndboak 1,. 1 . 1973 1.

The I>ay of Industrial and Scicntific Revolutions

I n the 1 sth and 1 91h ceniuries. sver;11 discoveries \c.ere made aboui lurninescsnce of inorganic cornpounds.

I n 176s. J . Cantcin made an improvrd phosphor b~ heritinf ground oystcr shells with sulphur." In 1852. G.

Stokes discovercd rhrit the minrrril tluorsprir converts short \\aveIengrh radiation to longer waveleneth

rridirition. The trrm/Trtorcsce~i~-c. \va'; proposcd by Stokes. In 1866. T. Sidot made the first stable sulphide

phosphtir by heriting zinc o'ridt. (%no) \rith h l d r o ~ e n sulphide (H2S) . The product wris zinc sulphide (ZnS)

2s It is intcresting 10 note thrit. in rrcent years. many luminescent materials have been made by adding gold

ris an activaior. .Alsu some rrirth elernenrs uscd ris components o f phosphors arc more costIy than gold- Europium. for example. containcd ris rictivator in the red phosphor for color television sets. has besn trtided rit a highcr price than gold. (By1er.W.H. Pigrtietir Hmicfbook iv. 1. 1973). ' 4 8 - Produccd calcium su1 phide (Cas ). ( B ylcr.\i'.H. Pigtrictlr Hctridmok i?. 1. 1973).

w thiit .ictii:illy containcd a t race o f c o p p e r (Cu) . In IS66. A. l?erneuil provcd thrit pure calcium sulphide

(CAS) \ \A non-luminescent. and in 1870. the tirst ciimmcrcial phosphor CriS:Bi t Balmain's paint) appcarcd

cm thc rt1.irkr.t. (Bylcr.\f'.tI. Pl,ytlrmr f lmir l l~ool; 1.. 1. 197-3 1.

Durin: rhc firbt qurirtcr of the 20''' ccntury. pliosphors u z r r nu[ used in large quantitics but somc sipi t icr int

~ ippl ica i i~ms \\r.rc d ~ v e l ~ p c d . Eciiiicin ti>und an ripplicrition ot'crilcium tungstatr. " for S-rriy intensit).ing

>irccnh (Bylcr.\\'.I.i. P;,SIIILVII Ht~trr l fmok \.. 1 . 1973). Thi s application still ccminucs today. An N-ray

intensii!inp screen enables high contrast X-rriy photography [O take place using ri l o ~ v energ:, X-ray source

r ;Ve.Dlerrc> 's Hcc~rclbook. 1977) (Mrtrttctrl o f Piroroyrtrpily S" sd . 198s ). Barium platinocyrinide j' wris used in

. . S- ray tlu~,roscopic: (vir.\ving) scrccns." Radium (Ra ) combined with ZnS:Cu \vas d e ~ e l u p r d a s a self-

-. Iimiinous p i p e n t fi)r \{.ritch and clock dirils. This Icd tci the notorious radium poisoning '' crises of dia1

paintcr.s \\.ho pointed their p i n t brushes \vith t k i r lips. ( B ~ d e r . W . 1 ~ . Pigtlrenr H m c i b o u k i.. 1. 1973).

During ilic second quar t s r o f the 70'\cnturY and around the period of' WorId Ifrar I I ( 1939-1943).

t l uo rc~ icn t rnatt.ririls f i u n d rnriny rnilitary and industrial applications. The developmcnt of inorgrinic

Iluoresccnt materials kcpt pacc \vith the advancement of luminescence processes theory. and prirticulrirly

- - \\ ith thc advrincrmcnt o f t'nergy band ~heo ry " for soiid scats t e c h n o ~ o ~ ~ . ' ~ Oxysen-dominared-type

phosphors \vcrr dcvcloprd in ri variety of types and in large quantities tbr fluorescent Iarnps. (By1rr.W.H.

P~grricvrr f - l anc ihuk 1: 1 . 1973).

:1)

ZnS:Cu hcis green t luoresccncr t B y1er.W.H. Pi,qnrcrir Hrittc/book 1.. 1. 1973). : I CaIcium tungstate (\ 'I) . Ca04 iV . (Merc-k /trdc.r 1 0 ' ~ cd. I9S3. m o n o p p h no. 169 1 ). :: - * , - Barium platinous cprinidc. CJBriN4Pt. (Merc-k !tirle-r 10" cd. 19S3. monogrriph no. 99 1 ).

Koenr~en . ( r t f~v-ck /~,ric\- 1 0"' rd . 1 9S3. monogrriph no. 99 1 ). ii Radium is no longer used fc3r this purpose and srifer isotopes of radium rire ripplied. mostiy by machine. ( i3yler.\f1.1-1. Piglrrcnr HrittciDook 1.. 1 . 1973). : i Thc encrgy levcl variation ofe lec t rons in ri substrincc rire limitcd to ri certain range thrit is determincd by ttic crystcillinc structure o f the substance. (Elecrriccil E ~ r g i ~ w e r i r i g f i u ~ i d h o k 2"! ed. 1997. pp.5 10-503). t(, - Thc tcrrn "solid strite" perrains ri, the consrrucrion of elcctrrmic and optical circuits witli only solid rnritcririls. such as u i rc . g l u s and semiconductors. As rinr~thsr detlnition, i t mrrins a circuit that does not insludc vacuum nor gris-tillcd tubes. such a s rad111 tubes and cathode-ray tubes (CRT). (Elecrric-cd FI.Îcyrrlccr.irry I / ~ r r u / / ~ o n k 3'IJ cd. 1997. p. 1097) (Wcik.iM.H. 1997).

.-\lk;ilinc. carth sultidcs, particul:irly thc' phosphorrsccnt and IR srimulablc types. \vere used for military

purposc.h ri large s c d c durirtg if'orld N'ar I I . and wcrc signiticrint1). improvcd during the second quarter

01' the 20"' ccntur?. T h c w phohphors hclpcd military operations in limitcd lightinz ciwdirionh during air raid

b l a c l o u t ~ and callcd upon the s;imc catc'gory ot' phosphors. Xcw Jersey Zinc Coinpany \\lis the princtpaI

supplier ot'alkaline carth sultidcs during this pcriod and up thruugh the carly 1950s. (Byler,\V.H. Piptircrlr

lftrridl)ooX- 1.. 1 . 1973 1.

Dif'tcrent varieties o f ZnS and ZnSCdS phosphors were deveIopèd. Their applications ranged tiom

instrument rnonitor scrrens to pigments: for oscilloscopss. for rridar. teIevision tubes. for X-ray intensifying

tluoroscopic scrcens. for self-lumrnous instrument markings. for paints. for plastics. and s o on. (Byler.\V.l-i.

Pl yt~icvri Hmirl/>uoX. 1.. 1 . 1973 1.

During the third qurirter ot'thc 20"' crntury. the rilreridy k n o ~ n categories of i n o r ~ a n i c tluorescent rnritcrials

cunrinued to improve uh i l r new c a t e p r i r s \vers added. The .-R & D j' effort" (By1rr.W.H. Pi.qtrietir

Firrrrrl/)ook 1.. 1. 1973. p.907) in the tidd was intensitled by the rapid increase in economic imponance. b),

tlw rcco@tion 01- intrrcsting potcntial new applications and by the continuzd rrlationship of lurninèsccnce

theory to solid state theory. (By1er.W.H. Pignierir Hari~lhook 1.. 1. 1973).

The long atierzlow ZnS:Cu type 3s well as alkaline eanh sulphide type phosphors found many civilian

applications aficr World Wrir I I (By1rr.W.H. P,,qriie~tr ffmrll>ook 1.. 1 . 1973 j. ~ c d . " y e c n " and blue

phosphors wcrc Jcvelc)pcd steadily as the deniand for irnproved prirnriry colour phosphors neas created bg

rhc ridvtnt o f color tdevision (Byler.\V.H. P&nicut ffr~ttdbook i.. 1 . 1973) (Martindi1l.M.G. 19S8). ZnS:Cu

' Rcsr;~rch and dc\.clopmcnt. ( Lo~i~ytirrat Ct,~lrsl i Dicrioticlt~. 199 1 ). :., Yttrium ( Y ) oxy~ulphidc dopcd ivirh terbium (Tb) and a rrtre carth elernent. europium (Eu). < X1artindiIl.M.G. 19SS. p. ISS).

. Linc cadmium sulphide (ZnCJSj doped with copper (Cu). (MrirtindiIl.M.G. 19SS. p. ISS). :O Zinc sulphidc (ZnS) dopcd uith siivcr (Ag). (Martindill.M.G. 19SS. p. ISS).

I-Ùncticmril inorsanic Iurnint.sc.ent pigment5 w r z cilsu de\.cl~)pccl in the third qulirter ot'thr 20"' century.

Thesr: phobphors \vert. tound to hiive unique excitation-rcspc~nsc characteristics thât tvere s u i t ~ ~ b l e for

specitlc applications. ( Byler.Ur.H. Pigrnt.rir H ~ i ~ i r l u o o k 1,. 1. 1973 1.

Thcrmographic (heat-sensitive) type phosphors rire used a s ciirnznsional thermometers. Thesr types

ha \c bcen d e v e l q x d for highcr srnsiti\,ity and \ x i e d cornbinritions o f propenics for use over different

ranges of temperature since 1956. They srin detect. visualize. o r merisure temperature diffrrentials over

surface areris. Thcir uses includc nondestrucrivt. tssting of items such a s semiconductors \\.hue abnormal

hest patterns x e detecttiblc'. tesring of bondeci parts ivhers abnormal herit conductivity patterns crin be

t.isualized rit the surfrice. and rnrdicril ~ i p p l i ~ a t i o i i ~ \vhers d i s r ~ s e o r injury causes abnormal skin

rcmpcrature partcrns. ( Bylt.r.if'.H. Pigrrrcrir Htrtuil~rïok i.. 1. 1973 ).

1nircirt.d quenching ( IR-quenchinsf type phosphors are used in an autornaric dodging photographic primer

rhat kas dc.velopcd by ifratson Electronics and Ensincerins Co- in the Irite 1950s and patented later.

Infrared qucnching pigment is incorporrited in rhe screen used a s an illumination source for photographic

prinring. The scrsen is escited by a uniform ultrriviolct light rind is quenched by infmed radiation

srrnultaneously. A s ;i result. the printrd image is llattsned (dodgeci) \vhile the contrast edges are enhanced.

thus prcserving vital information which otherwisr: \vouId be rnisscd in th<: overly light or dark portions o f

ordinary prints. Thrs type of printsr is uscd tor xririI photography. including the space program and

niiliiary rèconnaissrincc. (Byler.\V.l-i. Pignrcirr Hrr~lrllmok r.. 1 . 19733.

!.uriiiric~~c.rit pigmcnth thrtt r q x m d onl> t o ulrrriviolct Itghr ncre clcvcloped t h irrtcing atmosphcric airtlotv

ai StrinÏcxJ Vni\.crbity in the c.arl'* lC15r)h. S m n standmi ZnS:Cu and ZnCdS:Cu pigments wcrc applied to

air p~~lliiriiin studies and u.txc alsct uhcd in thc studies. .-1notht.r use o f this critegory is automatic mail

h~indling ?;>.?;rt.rns. Lurninciiccnt pigments. ris nxll as high tiequency fields and magnetic inks. arc: hvoured

6)r their hiniplicity. relative1 Ion. cr)st. and rclritivc invisibiliry. ZnS:Cu and ZnS:Mn pigments have been

u x d in sonw counrrics. The Unitcd States Posr Oiticr ha5 usrd zinc silicate '" and calcium sili~ritc.~'

< U~.lt.r.i\'.H. Pi.qvrrrrtr //trmlbonX i: 1 . 1973 1.

3. 2 . 1 . tlistory of Daylight Fluorescent Pigments

"Probribl'. rhc. firhr person rt) discover the commercial possibilitics ofdaylisht tluorescent pigments \vas

A c ) rhc tirbt onc to clip ri piecc ot-silk inro a dilutc rhodrirnint. dye-bath." as Voedisch speculritrs, drhough

n o onr: ih surc whcn this h3ppcnc.d. (\'oedisch.R.W. Pi~trietu H<tncfbook 1.. 1. 1973. p.896).

In 192s Kummrrcr nateci chat many d y e w i i s in aqucous solution showcd tluorescrnce in fui1 daylight. In

1932 Sisley found that sornr dyes. such ris rbodxnine on silk. made the fabric tluvrescent in h1l driylight.

\i'ith c w r i n ~ s , trriftic signs u w r made to fluoresce undsr mercury vapor Iarnps at night. and those

t1uorr:sccnr watings ~ v r r e rnanufrictured by dissolving small rimounts of rhodamine in glyceryl phthrilate

lxqucrs. Prior ro World War I I (1939-1945). the so-callcd dnylight rfuorescsnt rnriterials were used mostly

ti)r rrstilt.~ and traffic signs. During Worid War II. both sides used ground-to-air signal panels that were

fabricatrd by dyeing or coriring acetate fabric with tluorescent dyes. In those days. driyIight fluorescent

colours \vue rivailable only as liquid dyss. thersfore. their applications were limited to fribrics or resins that

r n i s d with the dyes wiihout quenching the dye's fluorescence. Those dyes were extrcmsly fugitive to

sunl i~ht . I Vocdisch.R.W. PÏgurcrrr I-l~~ridbook 1.. 1. 1973).

" OSiZn, ( i t l ~ n r - c X - 1tide.i- 10'" cd. 19S3. monogrriph no. 99641. J' CriS10~. Cri-SiO,. or Cri;Si05. ln&\- IO"' cd. 19S3. monogrriph no. 1680).

The lir'r ct~rnniercially avriilahlc d q l i f h t tlirorescent rnatcrial was tluorrsccnt brightznzrs (optical

brigt11c'nr.r~) for ~vashing po~vdrrs . This hsppcncd in thc 1930s b e l i n driylight fluorescent pigments u-ith

rcsin cLirricr5 Lverc invcnted. i M;irtindill.M.G. IOSS).

.-lrcwnd 1930. G. Widmer '' \vas tvorking to tÏnd a tvay of making soIid pigments frorn daylight tluorescenr

d ~ c s . 1 Ic rried t o makc pigment', by mixing \farious dyrstuffs. including rhodrirnine. into aminc rcsins. In

th13 czprrrimcnr. rhcdxnine did not exhibit suitisient f1uorcs~t.nc.r in the rrsins although the concentration

\r 2s ripprt)priatr t'or rhudrirnint. IO tluoresce in conventional dye solurions. Tannic acid and tartar emrric

uscd as ~Ïsatives or prrcipiration risenu criuscd most of the tluorescence to disapperir. (Voedisch.R.W.

PI : .mv i r Nmtibook 1.. 1 . 1973).

In thc 1930s. J. L. S\vitzer a t m sc~ught a mcthod to mrinufricturs tluorescrnt paints rhar glow undrr

ultrli\.iolet lizht. By 19-40. 3. L. S\virzer and hls brother started to producr dayliehr fluorescenr pigments. By

1947 the SLvitzers' daylight tluorcscent pigments became suprrior to the dyed Iacqur=rs of the earlier days

ri3 imprn\.cd light srability and tveathsr resistancr \ t u e irnparted. The , established ri Company ro

m:inufacture dq l igh r t l u ~ ~ r r s c e n t pigments and the company svrntually beczirnç Day-Glo Color Corp. The

S\i,itzer brothrrs wçrs succrssful because r h q did not use precipitation agents and bccause the

conct.ntration of 'dycs \vas Iwv. The? rnanaged to makr pigments sulid usin: mriteririls brised on infusible

urca and melamine resins. T h e Snitzer formula {vas innovcit i \~ in chose dayb. hotvrver. their products were

siill so unsrriblc that the products fadrd outdoors in a pcriod as s h o n a s 30 days. Also. i r was difticulr to

proces5 those pismcnts IO a reasonably small particle s i x by grinding. (Desiglifilg tr-irlr Duy-Glo C o l o r .

199s. pp.52-56) IE1lis.M.H.. et al. ( 1) 1999) (Voedisch.R.Nr. Pi.gttietrr Hnncilrook iv. 1 . 1973). Probably. the

rimount Sri.itzsr brorhcrs had produced by 1917 was siill 100 small to have an econornical impact. Voedisch

stcttrs. "Driylight tluorescenr pigments were nc)t produccd in the United States until around 191S."

(\'ocdisch.R.W. Pi.pnterir Hmidlrook 1. 1973. p.S95).

-1 : Vocdisch considers Widmer as the tirsr person who conczivrd of the idea o f a resinous rnolecule ris a w b ~ t r a k for ri dye (Voedisch.R.W. Pignienr I /~~cir iuook v. 1 . 1973. p.S96).

In tlic I96O';. ;t nc\r tht.rmopl:ihtic resin. b r i d on a mditieci sulphonriniidc. w.;is intrc~duct.d ri> tlir. body of

d;i>~li~tir tluoresccnt pigrncnts. This type 01' resin, o rgan~c glass, 1s tririble 2nd cm bc ground to \ery smriII

pxticlc ~ z c . l ' h ~ o r g n l c glass 1) pc rt.51n carricrs d s o subs~clncially impro\.rd thc Iightt'cistness ot'daylight

tluorcsc'cnt pisments; cornparrd r i > the oldcr types of'rcbin. the new type resins hriic ri highrr qucnchinz

ttirchhold in d y c~rnccnrration. "' N s o . the ncw resins are t lu imscrnt rhr.rnsclves; the resins absorb

uItrclvio1r.t Iight J' and rc-cmit the ribmrbsd snergy rit thc region ivhcrrr: the tluorescent dyes rtbsorb

intcnsciy. The high dye concentrririon and the additional excitation radiation from the resin increrised the

intensity o f the tluorescence trom fhe pigments. This type of rssin becrime the most important c a t e p r y of

pigment carrier in the t1uc)rcscent colour industry. (Vocdisch,R.\ir. Pigt~irrtr Hcrticibuok il. 1. 1973).

D'r~.-Glo ih acturiliy the namc 01' ri priint mrinutacturin~ cornpan).. but thc nrirne tends to be used as if it ivere

;i grrnrrril adjr.ctivr' t t ) rcplricr: the sumbersomr. ivordjlitorcrscwtr. For commercial purposcs. mrinufricturers

01- t luurr~scnt items rnighr ivish tc) usc colour names that rire similrir to day-glow. .A product nams "Day

Glow I'rbt" (Grand Pris Equestririn Products) irnmediatrly indicrttcrs thrit the vrsr is made o f driylight

1luorcsct.nr rnriteririls. In an iniormal conversation. an espression such a s '-Day-Glu paint" is used [O mean

"daylight tluorcscsnt paint in gcnerril terms" evsn arnong professional conservators. .As ihcw examples

indicrite. Day-Gto, bnth the Company and its products. have had ri signiticant influence urhere driylight

tluurescmt pigments rire concerned. T h e dcvstopment and the social impact o f driylight fluorescmt

pignients crin bc traced through the history of Day-Glo. (EI1is.M.H.. e t al. ( 1 1 1999) (EIlis.h.1.H.. et al. ( 2 )

1999 j .

** - I'hc m i m I I I ~ dyc 13 c imccn t r ; t t d thc more lightiast the pigment is. (Sni1ch.T. 19S2). L > . I'he r c sn ribsorbs ultravioict light at wavclengths shortcr than tht. dyes' c.scitation \ï;ivelengths. This rncans rtiat ille dycs art. prorccted l lnm ultraviolet light at shortcr wrti~rlcngths thrit are dcrrimcntril to dyss. ~Ellis.M.li.. ct al. ( 1 ) 1999).

In 1934. Jor Sui tzer and his bn,rhcr. Bob. s t m c d their hsr~w!. "The S\s.itzcr Brothers Ultra \ ' i dc t

1-rtborriic,ries" (I)csigriiti,r; ir-irli Drr-Glu Color-. 199s. p.52 1. Thci r tluorescrnt products wers sold for

hpcciat ef'l'ects in rnagic and stage shwt.s. rhcatrir dc.cr)raticms 2nd costumes. department store displays. and

in mo\-ic posrers: hcnrever. their production tvss. ris ri rnrittcr ~ ~ f t r i c t . running rn their frtmily kitchen with a

ubstantilil support tiom their mother. In 1936. the brothers becarne riasocirited isith a tïrm in Cleizlrind.

Ohro, C. S. A.. lvhich produccd and printcd mavie posters f;v Hc~11~x.ood. During the 1940s. the S\vitztx

hrorhers werc rclerised t i om the contrricr ivirh the poster prinrjng cornpriny upon the printer's conclusion

thrit tluc~rescent colours \couid not brin2 any more protits. T h e S~\vitzcrs retainsd al1 rights to their

I luorcsxnt t c chno lo~y . Th i s scrback rnotivritcd the S\vitzer brothers further. ( 0 r . s i ~ t i i t l g ir'irit DUJ-GIO

COlOf. 199s. pp.52-33 ) (Ell i~.bI . t l . . et ril. ( 1 ) 1999).

l ' h c instrtbility ot'dayLight tluorescent pigmsnts tc, hrat and Iight \vas ci serious technical problem for the

m;inutrtcturers. The industry \vas also challengeci by the hi$ ra\v rnrtterid c w . small barch s i x . hish

proceshing c~st . ; and the cost fur rtdvsrtisrmcnt tc, crerite dernrind h r its products. In one estirnate. ri

pigment rnanuhcturrlr had to spend 6-S 54 7rf the compriny's yoss re\.enue for rtdvenisernent. and about 10

'.ï fC)r rcscrirch and drveloprnent. In rerility. the sriles ofdaylight tluoresccnt pigments in the United States

\vcrc very Io\\ until sr)mc.timz in the 1950s. (\'cxdisch.R.\i'. Pi.yttrctir H<r~rtibooX: Y. 1. 1973).

.-II thc beynning o f the venture. the S~vitzcr brorhers expcrirnmtcd \vith diifereni meihods of combining

d y c ~ and rcsins rii producè a ne\\. type c ~ f colorant thrit glo\vb under ultrriviolct lirht. Soon they made ri more

Lluririg \\.orlcf \Var I I . the S\\-itzer brothcrh' ct)nipany conccntrritcd c m manut'ticturing bright visual

'iigri;lling pinels. This appl~crit im not only brcught the tirsr niajur succcss 10 the compriny. but also srived

niLin! yc.opIc"; lives during the \var. Th<: S\vitzcrs dcmunstrrircd thar tluorescent pigments could bc

dt~tingui~heii \\.;th hich colour saturation as long as they uere visible. uhsreris coniw-itionril non-

fluure?;it.nt signal coIr)urs rippeared gray or blrick rit distances. The Suitzrrs ' products \vers ustid for the

ci)mrnunicriricm bei\vecn ?round forces and aircraft to prcvent the inadvertent bornbing of allied rroops.

i 1)c, .si .y1tt11y \ r . i f I~ Da!-Gln Color-. 1998. p.53 1.

Ligtitfristnc.~~ hrid bccn a mqor tcchnical problcm nith driylight tluorescent pisments. but i t \vas ovsrcomc

tu somc csrent shorrly riitrr World \Var 11 tvhen the cornrnsrcial interest h r thoss pigments u a s shrinking.

In 1946. rhe Swi tzer brothcrs' businrss tvris incorporated as Sn.irzt.r Bros. Inc.. and formally founded 3s a

cimprin>,. The company \\.ris srived by their on-n techncilogy for signriling panels used during the \var. The

briithctrb used the sclrne recfinolwy tu create colorants for ourdoor billboards so thar the messages would

- j ump oti the board." ( Dcsigtiaig w i i l ~ Dtv-Glu Color. 199s. p.5-l). T h e debur of daylight tluorescent

col~)rb c m ri billborird \\(a'; in Canada in 1947. Thc advertising industry was stimulrited immediately and

subrnittcd ri barrage of orders h r "the siIkscrcen colors that could be seen at a distance. glowing brishtiy rtt

J:itvn or ciusk. Ions rifter other hues hded to grriys." (Dcsic~tiilig br-irlr Da!-Glo Calot-. 199s. pp.53-51).

The Su.irzers' business begrin to grow in 1950s. 4t the tirne, printers and ink makers !vers still in doubt

about the printability ot'thc S\vitzers' new lithogrriphic inks and bases. In order ro prnctrritt. into the

indiffcrcnt printing market. il \vas nrcessary to convincc desirners and manuhciurers to use daylight

tlur>rc.sccnt cdours t i ~ r prickriging. The Switzrrs' catchphrase was "Fluorescent colorus could virtually

wirli niir;lcles for thcir prcidusrs." ( Dcsi,ytiirig it'irll Da--Glu Color. 1998. p.54).

I I I 1991. Pi-osicir ,!! G;imbIc t lnr i l l~ pt.rsu;icicd t o a iccp t tluorrsccnt coluurs for packages o f its productb

:i?~ ;i rrrd. The r e d t \ras rcmark;ible. T idc dctergent c anons o f Proctor Sr Garnblr stc~od out on supermarket

d ~ c l i c s . Thc. iiinirncrciril p o ~ c r r)l'd+,light tluorescent packrigss suddcniy became w iden t and orher

niliniilliirurcrs wcrc drivcn r o use tluortisient colours so thrtt they N W I I ~ not be left with their dull-tooking

rradition;il p ~ c k r i g c ~ hchind thcir compcritars. The rnanufacturing t e c h n o l o g o f driylight tluorçscent

p ~ y m c r i t ~ ~ ~ n p r o w d . and rhcir applicaricinb txprinded bcyond printing. into advertising. into sritkty. into

prurnuti t~ri~l materilils and cigain. into milirary uses. "The cunipany dzveloped tluorescrnt pciints for [ the]

L!. S. Air Forcc and [ the U. S. Nrivy militrtry riircraft. T h e priint was ripplied in bands to the fuselage. \vins';

and tail t o prevent midair collisions. O n e year after the implementation o f the tluorrsccnt paint pro, "rrirn.

miJ;iir ciillision dropptid t o zero in .Air Trainin2 Commrind tlights." (Dexi,qtiiti.q it-irh Dny-Glo Color. 199s.

p 35 i . Ttic i.cirnp:in> rhcn cicveloped pigments for plahtics in tirne to y v c ri f lou1 to Hula Hoops. Frisbecs.

B ig \\'iicclh mci inany o ther ti i!~. i DL'SI ytlÏt1.y I ~ Y C I I Du>.-Giu Coiur. 199s. pp.54-55).

.The niimc Day-Glo \vas rrridernrirked in ref trrnce to the cohr's daylight tluorescrnt propenies. The nrime

cciughr on. and in the iatc 1960s. t!is cornpriny forrnally chringcd irs nrime to Day-Glo Color Corp.-*

I Bc.sl,qlrrli y ~i.lr11 Dtzj.-GIo Color. 199s. p.55). In the 1960s. thc company kept o n incrrasing their lines

c r i j o~ ing ncw dernands: Blaze Orange \vas adoptrd a s a colour for traffic conrs . srtfrty vesrs and othçr

ha1'cty cqulpmcnt. Fashion and prickaging were intluenced the contemporriry anists. such as Pr te r Max and

And' [Varhot. \\.ho uscd driylight tluorescent colours extcnsivdy and ushercd youths into the epochal

~'psyclieddiç" trend. In the 1970s. the cornpan? discovercd a liehtfrist yellow d y e " and the dye wris used

tr produition ofco lour fu l soif balls and tennis ba11s.~' In 19s 1. the Drty-Glo company introducsd specialty

irik vchiclcs. additives. c)\.erprint varnishes and riqueous coatings. During i_hc 1980s. tluorescent colours

bccrirnt. t'ashionablt. in clothing. and rittracted continuous demrinds for daylight tluorescent pigments. Sports

tiutt?ts bcirime fashionable items. and the combinarion o f srifety awrireness and frtshion consciousnrss

:O - . - Thc source does not inciicats ihis as ! l u ~ r e s ~ e n t ytfllow. ( D c s i p i n g with Drry-GI» Color. 1998. p.55).

The standard çolour tiir tennis b d l s \vas chringed from white ro yellow. (Dcsigning wirh Day-Glo Color. 199s. p.55).

3. Colour Science

Colour Theory

3- 1. 1. ilistory of Colour Tlicory

.I'hec)rrcs about thc rclritiunbhip rimong colours have bsrn intluencsd by relisions and philowphy. Many

ycoplc hrive esplriined the rr=lritic)nship rimong colours ris it'colour cmbrriccd the sntire universe. and the?

prtsrnird thrir solour theor? ris colour dirigrmis rhrit Lvere the rnrips of their colour \vorlds. Some of thoss

~incicnt wlour thcories uerc rtithtlr creativr but others wrrs scientific. These creritive and scirntitic solour

thcorics h ; ~ v ~ . ;tttmcted the rittenticm of scholars cwer m3ny centuries. and eventurilly. todriy's colour theory

ilri:, c \ u l \ d tiom their predecessors' ivork. For esrirnple. the cotuur scientist Gerritsen shou.s ho\$, the

concept of colour hris changrd in \Vrstern cutrure. usin? ;i collection ofcolour dirigrrims (Gerritst.n.F. 19S3.

pp.2 1-34). (Figure 9 (a)-(dl )-

Cicrritacn secs the inlluence of the old Greek philosophy on some colour dirigrtms drrinm in rincirnt tirnes.'"

Tticsr dirigranis hri\.c white ! Albus) on one end of the dirigrrim. blrick (Niger) on the othcr end, rcd

(Rubrus) and green (Viridis) around the middle bèt\cecn tvhitts and blrick. ):cllc)\\~ (Firivus) nrrir white and

bluc tC;\cruleus) nrrir black. White represents the Iight of the da?. blrick represents the drirkness of the

Ah Gerritscn ducs not spccil-. which diagrims werr influençed by Grcek idcris but thc diagrims drawn by :Igutlunius (AD. 1613) and by Kirchrr ( A.D. 1646) ripprrir to have an influence f i r m Greeks.

Inicre~tingly. thc colours in rhc dixgram rncnrimed above arc a l~gncd in the o rd r r 01' the brightncbs 01. the

nio\r situratcd coI~)ur~> in rhc 3 l u n ~ c l l Colm- Solid (Figure 9 ( c ) ). In XIunseII's theor). the brishtnebs o i the

moht ssturritcd rcd ;tnd rhc most saturatrd g rwn cimespond r i ) greys ~ ' i t h intermediate brighrness on the

grey sc'alc. thc mosr saturated yrllow corresponds to a brishr grcy, and the mosr saturatcd blus corresponds

t o ri du!, grey.

On the onc hand. \Vitdo (born in .-1.D. 12-40) sri11 believcd rhrit red \$.as made o f thc misture of \\,hite and

hlack. and on the other hrind. .+lristotle ( born in B.C. 360) ha3 already disco\*ered chat yellow resulrs tiom

thc "nrf;lrness" (Gr.rritsen.F. 19S3. p. 15) of red (Rufus) and green (I'iridis). Aristoile's theor! rigrecs wirh

the systcm in the human visual q a n . Dei13 Porta. in AD. 1593. discovrrt.d and recordcd the colour

scquenct. of the rainbow in the lighr refracted by a prism. and also creatcd ri colour dirigrrim. (Gerritsen-F.

19S3. pp. 13-25).

Xwtcin'h colr)ur diagram dra~km in AD. 1660 (Gerritsen.F. 19S3. p.2 1 ) kritures the sequrnsr of the seven

rriinbow colours in ri circlc and tvhitr: in the centre. This dirigrim appcars similar tu ivhat we todtig cal1 rhs

colour tvheel with thrce primary colours and three cornplementriry colours o f the primary coIours

(:\gohton.G.i\. I9S7,. The CIE '" 193 1 ( ~ y ) chromaticity diasram is evzn closer to r\ieu.ton's diagram in

rc:arJ 10 the p<)sition u i tvhite. Xavton drcw this dirigram only fburteen yerirs ritter Kirchsr sspressed his

Grcck-intluenccd point of' vieu. in colour ihrory. This revrrilb how revolutionriry Newron as for people in

those days. This rilso rèveals that academic advancernent did not proceed uniformly clsewhcre in the world.

<'J - rhc Commission Intrrnationale dqEclairage.

ïu Kelly's rnap for dcterrnining the colour namzs o f light (Xgosron.G..A. 1987. p. 67) would be the best

refsrcnce (Figure 23 1.

Ttic ni:ijtv cliitkrcncc bct\vct.n Nc~vton':, colour thcory and modern c o l m r throry is that Newtr~n did no[

i i ) i i i t ~ lii11-plc. or n1;Igent:i. in his diagram. i-Icrc.. purplt. ii; diiierent licim \.iolet. Violet. in modern colour

rhcory. 14 the colour 01'munochromat1c light that ~icçupies the shortest \~.avelensth range of the visible

region. betneen bluc and ultrriviolet. Purplc: is perceivrd uhen ri-d light ( long \vavelengths in the visible

region, :mi bluc Iizht (short uavclsngths in thr visible region 1 are cornbined. but purple cannot be

pc r~e~ \eCI nithin a hingle wavclcngth range of lipht. Purple dors not exist o n the rriinbow." Purpie is a riori-

. s p ~ . r r d L - ~ l ~ l i r (Xgoston.G..-\. 19S7. pp.56-60). In the practicr o f paint rnixing. however. drtrk blue rni.usd

tviih a lirrlr red is called violet and if more rcd is ridded to violet. the coiour becomrs purple. thrrefore. the

coIc>ur n;lmes of' vidt.t and purple map not be rilways distinyished frorn each other (Gerritsen.F. 1983.

p.20.l.

People sicirrsd to consrruct thc concept of a threr: dimensional colour world bsfore the Iast qurirter of the

1 s'!' ccntur'.. but the old ripprorich to colour \vas still alive and two dimensioncil colour diagrams krpt

appertring. .&fier Kcn,ton's culour diagrarn 16601. \f'rtller ( 16S6). Goethe ( 1793). Herschel ( lS17) .

Schrcibcr ( 1 S-40). hlaswell ( 1 S57). Rood ( 1579, pressntrd a rhree dimensional colour diagram later) and

Klee f 1934) al1 devrloped nvo dimensional colour throries. Finally. the CIE 193 1 (K. y) colour triangle \vas

r i l m two dimensionril. The fi>Ilo\vin~ names nith dates are the scholars who prssented three dimensional

colour systrrns: Lambert ( 1772). Runge ( 1 S 10). Chevreul ( 1 S39). Wundt ( lS74). Von Bezold ( 1876).

[Iiitlcr ( 1 SS3). Titchencr (1887). Wundt ( IS93) . Ebbinshrius (1902). Munsc11 (1905). Rood (1910). Munsell

(again. 19 15 ), Ostwald ( 19 17). Boring ( 1929). Pope ( 1929). Johansson ( 1939). Hesselgren ( 1955). and

1-i5rd ( 196s). Mort. three dimensional colour sustems, or colour spaces. have been created based on the CIE

i93 1 (s. y) c o l w r tricingle: Mac Adam ( 1935). Hicksthisr ( 1940). Rosch ( 1953). Luther-Nyberg (ca. 1955).

Küppcrs ( 1972). and Gerritsen ( 1975). The CIE also presented ri threr: dimensional colour spacc riround

1953 (Gcrritsen-F. 19S3. pp. 13-25 ).

\ l . I'riblc 5 shwrs the colour order in the rainbow and the hue wavelengths ot ' these çolours.

"Scicrititi~ riqxxrs of the phrnt)menon of co l r~ r perception have capturrd the intcresi o f rirtists. musicians.

:tnd \\i.irerb during thc priht t\r,o ccn~urizs." as colour scirntist Agoston states (t1goston.G ..A. p. 1 ). .c\goston

Iisrs Il\-r. pwplc \vho contributcd r i ) the dcvclupmrnt i)f colour science ris tidlows.

. . Gocihc. ' rt Gcrmrin p ~ w . publishcd ri book entitled "FUI-Dc.!ilcltr (Thcory of Colc~rs)" ( IS 10). This book

c.onr:iin'; hi5 man? dctriiled obwrvatic)ns about colour perception. This book "may corne to be recognized

35 fiiresh;lcfwing. howxver dimly. the ncst important advance in the throry of color." (r\pst~)n.G..A. 19S7.

pl I ~iccording to 3 prominent colour authority Drine B. Judd ( 1900- 1972) (Agoston,G.A. 19S7. pp. 1-4).

J.11.ii '. Turner produccd sorne wrnpositlons nith knowledgt: lerirncd from Goethe's book on colour. H e

n.15 ;ilho inrt.rt.std in the \iork ot'thc scirntist-mathemarician Issac Ne\vron on light and colour. as rcad

i r ~ m i hi5 iecturr: note:, at the Royal Acadcmy. (.Agoston.G.X. 19S7. pp. 1-4).

~Iichel-Eug?ne Chevreul \vas a chernisr and director of the dye housés of the Gobslin Tapestry Works.

ourside ( non. i n~ d e ) Paris. and \r.rott. ri book rnrirlsd "De lu loi A r corlrrcrsre ri~mtirmr' des couierirs (The

Principlcs ot' Hrirmony and Contrust o f Colours)" ( 1839). Eugène Delacroix ripplied principles thrit he hrid

Itirirned (rom this book. Latrr. Josef Albers ( ISSS-1976). an rirtist rit Yale Uni\.ersity. brou@ people's

- * rittt.nrion to Chevrrul's culour thcory again. The O p artists -'" cldded to this trend bp seeking the rschniqurs

ti)r enhrincing the brill iant tippsarrinces of colours (Agosron.G..A. 1987. pp. 1-4).

Osden Xicholris Rood \vas an Arnerican artist-physicist. Influenced strongly by his book "rl.loriert~

C'1:rorri~~rics" ( 1 S79) \vert: neo-irnpressionists Georges Seurat and Paul Signac. who appIied rheir

knotvltidgt. in their divisionistic paintings (Agoston.G.A. 19S7. pp. 1-4).

5' Cricthc's colour dirigram (Gcnitsen.F. 1983) is similar ro modern colour \vhecl (Agoston.G.A. 19S7) i f

Gi)t.thr's r d (Rot) is rep1rict.d with purple rhar is called magenra. and if bluc (Blau) is regardrd ris greenish blue thrit is callrd cyan. Somctimcs violet-blue (ultramarine) is a lso called "bluc." -1

Op :irr is :i genre of modern art thrit plays visual tricks (Longman Dictionary. 1991).

A I 1. X1unsc.ll ( 185s- 19 1 S ). artiht. \vas trustratcd with the SI»\\ advancement o f colour theory. While

tc ;~ch~ny 31 the kIassichust.tts Normal Art School (nom the Slassachusetts Col lcge of Art. Boston}. Munwll

&\clopeci his colour thcor', \vith LI ne\\ colour rnapping systcm. Initially, The Munsell Color Systern \ix,

intendcd 11, bc ri s x m t i t i c teaching aid. but i t has earned unirersal recognition ti-om the coiour industry and

the xricicmic cornmunit>. ( .-\go>ton.G..-1. 19S7. pp. 1-4 ).

At ~ i h ~ ) c ) l s . i t took dccades for cc)lr)ur scicnce tc) establish itss!i in fine art education. Colour scicnce

cduciirion \vas started in the early 1900s by terichers such a s Drnman Ross ( 1853-1977). teacher of art and

design at Harvard University (Cambridge. Massachusetts) and Byron Culver ( 1894- 197 1). the Depanment

of Xpplied Art at the Rochester Atheneurn and Mschanics Institute (now the Rochester Instituts o f

Tcchnolwy. Rochester. Xew j'urk). Many of their co l l rqpx ho~vever. did not feel cornforrctble ~ i t h

colour science nor were thry intcrested in it. Sporadic teachinp of colour science was stilI ri problem in

19-12 tvhen R.B. Flirnum (Rhode Island School of Design) conducted a survey on colour theory education.

Today. colour science is u.rll-rtxognised and is ragerly taught at art schools. Studies a n colour science

hri\.e bcen published by artists and te ri cher^.'^ The n e u d e ~ d o p n i e n t s in science and technology have had a

higniticrinr impact on today's rnoremcnt that faveurs science in art education. !Agoston.G.A. 19S7. p.?}.

In commerce and industry. colour ther~ry has been needed to spcciïy colour as a fcature o f materials and

producrs. Therr arc variuus colour sarnplr systems. including The Munsell Color System . ~v i th difkrcnt

tCarurcs for diverse applications. but these standardized systrms cornmonly have hundreds o f samples and

codes assigned to the colours. Thus. once a colour is matched to zi standard sample, the coiour is identitkd

and reprcsented by the corresponding code without bzing accompanied by the actual sample materiai. This

system is uselùl 10 specif'. colours in modern business communication where both precisrness and

cl't?cicricy are rcquired. but eschanging colour srimples fa ci lit art.^ ncithcr of'thcm. (Agoston.G.A. 19S7.

pp.3-4).

<4 Agoston cites the intci-national art journal L.eonarïfu as a source of articles on the subject of colour. thst c w r r s ropics rringing fiom contemporary visual art to science and technolwy (rZgoston.G..4. 1987. p.?).

Tiic C~irnniihhic)n Intrrnarioncilc d'Eclriirrigt' (CIE) rilso dcvcloped mcsthods for specibing colour thrit rire

~ntcrn:iticinrilly ; ~ c ~ ~ p t e d and widciy used. I'hc CIE'S colour systems idrntit'y and sl>cscib colourb urili~ing

rhc ~ ~ I ; I [ I \ . c am~)unts of thrre standard prirniiry colours for colour rnatching. The systcnis arc: bahcd o n rhr

tcict th;it thrcr primary colours crin be rnixcd io crcrite a coluur that matches the colour undsr examinrition.

! .-1gostc)n.G.A. l9S7. p.3). Furthermore. ris :lg~_oston notes. 'The CIE method has bren applird in subsidirtry

\\ri'.'; ;i5 \teII. sumc ;)f uhich are o f particular interest tu rirtists and designers. .... the CIE scheme is a

htcpping htont. to other schsrnes thrit providc for prrcise dercrrnination of colur dif'krrnces." i .-\go~[on.G..A.

1987. p.3,.

3. 1 . 2. Colour Systerns

i f 'hcn c~)lour is >tudicd scicnti ticrilly. colour rnusr bs understood and expressrd objrctivel>* so that the

rcbults tiom the biudy cire c~rrect ly undrrstood by othrrs. Vririous colour systrms have been devetopsd to

I'ricllitiit~. ri scirlntific and universril understanding of colour. Sorne important colour sysrsrns rire discussed

in this section. Also. the naturril colour systrrn is introduced to the readrr in Appendix II. sincr this colour

bysrern hris a unique approach to colour specification.

3lunscll's Colour Theory

"3Iunsrll irnplernc.nted his color systrm tvith ri l aye set of vcry ~ ~ r 1 ù I l y prrpared color sarnplrs. The

srimples tr.c.re rclared to one another through progressive changes of approximately equal steps of Hus.

\'cilue. and Chroma." This ts the essence of the Munsell Color System as surnmariscd by A= ooston.

( :\g~-"~ttm.G..-l. 1987. p.2). (Figurcs 19-2 1 ) .

A. t I . ?vlunsell ( 1 S5S- 19 1 S) was an anist and teachcr. In 1905 Munsell cornplriined of "the incongruence and

bizrirre naturc of our prcscnt color names" (t1goston.G.A. 19S7. p. 1 ). He rcasoned that color should "be

5upplicd wrth an appropriate systern bascd on rhc hue. value. and chroma ot'our sensations . . .

(:Igostcm.Ci.,-\. p. 1 ) , jus[ ris "niusic is equippcd with ri systrrn by lvhich it detines cach sound in terrns of i t ,

pitch. tnicnsity. and durrition." (:I~~)stun.G..-\. 1957. p. 1) .

>lunx l l devised a practicril color-notation systern to teach ccilwr sc ient i t ica l l to children: houw.sr . tvithin

sciu-ril CL-sdcs. his sustem bcctirnc. one of t h ~ moht recognisc.d mçans to spccify colours in colour science

2nd coloiir tcchnc)l~)gy. As Munscll h i r n d f proposeci. Thc .\lunseIl Colur Sysrrm crin be used for choosing

hiirrnt)niiw'; colours. Cotor harrricmy \cris also discusscd by Goethe. Chevreul. Rocid. Ostuald. Judd.

Ii'>.szt.chi, Burnhrim. I.4anes and Bartleson. (.Aposton.G..\. 1957. pp. 1-2).

The k!unseII Cotor System is the rnost important colour srirnple system currently used in the United Stateb.

Thc ~Iunst .I l Notation has besn incurporated in the Standards of the American National Standards Institutr

and thc .-1merican Society tvr Trsring and h4atcrials. A s 1vcI1. both thc Japanese colour standards and the

stmdard colour designarion of the British Standards Institute for paints rire based o n the ~MunselI Notation.

i Agoston.G..-1. 1937. p. 1 14)-

The .\lirr~scll Book of Color (tv..o volumes) is a collection of colour chips produced a s srirnples of the

hIunsc.ll Standard Colours. The samplrs are also rivailable as cards in t?Ie boxes. a s loose shests. o r as

stucient 'iris th31 consist 01' incxpensi\.c srnrill srimplcs of !es5 than standard quality (rnatt-tinibh onIy). There

arc two cc)Ilections of standard ptiinred sarnplcs for the ~Munssll Color System: a ma t t -h i sh collection

icibciut 1325 colour chips) and a glossy-finish collection (about 1600 colour chips). Both collections are

increascd whcnever more saturatrd pigments of acceptable permanence becorne nvailable. (Ag0ston.G.A.

1987. p.1 14).

In h4unsell's systsrn. as Xguston expIaincs. "surfrice colors rire identitled by three quantities: MuriseIl Hm.

ill~rr~.wll Cirrortru. and Murlsell \'dire. They permit quantitative specification of surfacc colors undrr

spcciticd condiiions of ' \ f iewins: average daylight (CIE ILL CI. 45' illumination. and vicuing d o n g a sight

Iinc pcrl~c.ndicul:ir r o the surt'rtcc. A neutral grri" backgrounJ 1s usually used when the color ot'a sample is

~Jcn~iliccl h l cornpriring i t s r rh hlunscll culor chips." (Agosti)n.G.r-1. 19S7. p. 1 I I ) .

1 Iucb Arc iiligned in a circlc in the Munsc.ll C t h r Systtm. Tlie Iiirc cil-cle contains ten liue rnrrxes and is

5ubdit.iJcJ by ti hundrcd equally s p x e d hrc mriii. The hue ranges are encoded with letters o f the alphabet

and o r d e r d sl~)ck\vise: rcd (R). yellow rcd (YR). yellau. O-). green yellow (GY). green (G). blue green

c DG). bluc (13). purplt: blue (PB). purple (Pj. and red purpls (RP). One hue rangs stans with its hue radius O

n.ht:re ancrthcr hue rrinse ends \spith irs huc radius 10. Erich hue is assigned ri liite rutfius rirutiber that is

folIoutxi by the alphabetka! code of the hue range. for example. 2B (the hue on the hue radius number 2 in

the hue rringc ot'blue) and 6j.R (the hue on the hue radius number 6 in the hue range of yellow red). in the

middlt: oi :i hue range. r, ttmjot- Iirtr is located rilong the hue rridius 5. (Agoston.G.A. 1957. pp. 114-123).

Froni 3Izis\vell Triangle to the CIE Chrornaticity Diagrrini

The CIE 193 1 (s. y J Colour Dirigram \\.ris rilretidy mentioned in the section "History of Colour Theory."

This type of diagrrim. or colour mapping. is called the clrror~itrrici~ tlic~grnrrr. The chromaticity diagram is

"in universal usc in commcrce. industry. and science and nosv appsaring in liierature intrnded for artists

and designers" (.Agoston.G..r\. 19S7. p.4S) as a rnethod for dsscribing colour by an objective and universal

rneasure. The basic Iosic to compose ri chromaticity d iq ra rn is that a perceived colour of li$r c m be

bynthcsisrd \r.ith three pr i rmn colo~trs (or jus[ yrittlnries). blue. green and red. Here. blue is a violer-blue

(or ultrarnririnc blue) as opposed to a greenish bluc. cyan. Colour is specified by the ratio of the prirnaty

colours rhat make up the colour. and the position of the colour in the diagram indicates the ratio of the

primary colours. (Agoston.G.A. 1987. p.47-5s) (Gerritsen-F. 1983. pp.65-67). (Figure 22) .

CoIour that is presented on the CIE 193 1 (x. y ) Chrornaticity Diagram is a combination of hue and chroma

in Munsell's w m s . Thc rrcr~tcil coloirrs are encloscd in the tongue shripcd border of the diapram. The

colt)urs that exist outside of this bordcr are d l e d ir~lcrgiimr\- coloctrs and are disregarded. Inside the border.

the c I ~ ) w r 10 thc bordcr the c d o ~ ~ r is I!W mort saturdtsd the d o u r is. T h e zero saturation point. o r the eclilal

p o ~ . c t - p ~ ~ r t r . I:, f c ~ ~ ~ d netir the centre of the x t u a l colour area. Hues a re aligned rilmg the tongue shaped

bc)rdcr. S~WL*IIUI CC,~OIII . .~- (c~)Ioiirs ot' lisht e x h of'ivhich c ~ n s i s t ~ o f a sinsle uaveIsngth ot' light as is

tijunci in thc rriinboiv) arc o n the arc of the diagram in the ordcr o f the ivavelength. strining ivith blue

(violci-blur o r ultramarine bIuc) rit the bottcm Irft. passing thruugh green at the summir and ending Lvirh

red rit the luiver right. The straight part or'thc border hosrs non-specrrczi colours such as purples and

purplish pinlis. Non-spectral colours are enc!cwd in a triangle that is enclosed by the straight part of the

bt)rdt.r and rhc t\\*o lines that ccmnect borh cnds ot' the straight line t o the zero saturation point. The arc is

called the spccrnwl Iocirr and the straight part of the border is called theprtrple litie. (Agoston.G.A. 1957.

pp.47-5s). (Figures 23-24).

T!ie amount of rcd. green and blue prirnary colours that make up the specirnen light must be driterrnined in

urder to locrite the specimen colour in the chrornaticity diagrrim. For this purpose. red. green and blue lights

rire projectrd and superimpossd on a ivhite surfrice to synthesisr the colour that is under examination. T h e

amdunt of light in three prirnary colours are changed until the synthesised colour matches the specimen

co1c)ur thrtt is projected beside the synthesised colour. Whrn the colour of the tivo light beams match. the

ratio o i r d . g c e n and blue prirnary colours in the synthesised colour is recorded: thus. the specimen colour

1 3 specitlsd ~vith numerical t i p r e s . and the colour can be expressed a s a plot on the çhromaticiry dirigram.

(.Asoston.G..A- 19S7) (Johnston-R.M. Pignic~rr Hclndbook r..3. 1973) (Judd.D.B., et al. 1963). (Figure 22) .

The prccursor o f the chromaticity diagram \vas the Maxwell TriangIe. an equilateral triangle (equal-sided

~rirtnglc. thrte corners rire rquai l s 60") with a prirnary colour of light o n each corner. The triangle \vas

ncimrld rit'rrr James Clrrk Maxwell. a Scottish physicist who applied a colour mixture diagrrim to his basic

ivork cin colour. O n the Maxwcll Triangle. the edges are used as three axes: the red-green axis. the green-

blue axis and the bluc-red axis. When a colour is on an edpe o f the triangle. the colour consists of two

primaricb. 'I'hc ratio of a primriry in the colour on an edgc is the distance between the plot of the colour and

< Y

Xgoston uses tht: rerms spmrcrl co!olir and spectrintt coiour intcrchangcably (Agoston.G.A. 1987).

- 4 4 -

thc orlia- end c ) f the axib ~vhere the c~ther prirnrtry colour is iucated. When s colour is insidc rhc trianzle. the

rxiici ot'tht. green primriry coit)urs is designateci by the point ~t.here the red-grecn axis mcets the line

cstcnded tiom the colour'b plot p;irallel to the blus-red asis. The amount of the green prirnrtry in the coIour

is the cfi3tanc.c bet~veen the crossing point on thc red-green asis rind the corner wirh the red prirnriry colour.

Tht rarit,s o f the other prirnary colours rire determinrd in the same way. (A=oston.G.X. 1987. pp.47-53).

(Figures 26-3 1 ) .

The former paragraph surnmariscd the accepted explanrition of the Maxwell triangle but it might confuse

rhe reader. It may be easier to understand Max\veIl's triangle if another sct of axes is used instsad of the

three cdges: red axis. green anis and blue axis. The red axis starts at the rniddle of the green-biue edge rind

ends rit the corncr with the red primary culour. The bottom of the triangle (the green-blue edgs) is zero red.

the summit of the triansle (the red corner) is pure red (no other primary colour is contained). and the point

Lvhcrc the line extended frorn the colour plot intsrcepts the red anis ai 90° is the ratio of the red primary in

that colour. A s tvell. the y e e n asis extends from the middls of the blue-red edgç to the green corner and the

blue u i s estends h m the middlr. of the red-grssn edze to the blue corner. AI1 three rixes strirt ~vith zero

and the rtmount of primary colours increase until these axes end rit the corners. A corner represrnts a pure

solour that consists of 100 % of ri sinfle prirnary colour.

The values thrit sxpress the ratio rimons the red. green and blue primary colours are relative rather than

ricrual or absolute figures (t4goston.G.A. 1987. pp.4S-53). There are no units applied to the Maxwell

Triansle (Agoston.G.A. 1987. pp.48-53). therefore. it is important that the ratio arnong the three primary

colours is presented accuratels in the gometry of the triangle. Ail thrse axes must have the same scale and

ri l l thrcs primary colours must have the srirnc maximum value 31 the corner. hrnce an equilrtvrril triangle is

used.

Thc CIE (X. Y. %) system is explaincd iveIl with the Maxwell Triangle. X is rissigncd as the relative

arnounr ot'rhe rcd primary colour. Y is the rclatrve amciunt of thc green primary colour. and Z is the relative

amount iiÏ the blue primary colour. Since thc amount 01-S. 1'. and Z are relative t c ) each othrr, S can br:

0.1. 10 o r 600 as long as Y and % arc rncasurcd \vith the sanie ';cale. I t is customary. hinvever. ro report )'

ri5 I O 0 ;inci report X and Z as the correspondin2 valuc.5. (.-lgi~on.G..4. 1957. pp.47-5s).

Thcrc. arc' 3 Ïe\v unique characteristics nith the CIE (S. )'. 2) systcm that cnablr:s the practicril application

01' thc thciiry. X, Y and Z in CIE'S systcm rire criIlrd the CIE Tt-islitrtfclirs I'crlncs tnstcrtd of the amount of

the prirnrtry colours. 'The primary cl~lours of light ussd by the CIE rire ca1lr.d i t l ~ ~ r g i t t c ~ r j p r i ~ t r a r i c , ~ . The

CIE'S im:iginary primaries can accommodate a11 colours that possibly exist in the wrivelength regios

ber~vèrn 400 nm and 700 nrn. including borh spectrai colours and non-spectmf colours. Agoston srates. " [ t

i b \vsII cstriblished thrit no threc primaries can. by rheir misrure. produce al1 colors" (Agoston.G..-1. 19S7.

p.53 1. This means that a pertecr garnut ivith a11 perceptible siilours cannor be crrated by using any set o f

thrw lisht bsams in prirnary colciurs that actually exist. It is possible to bring a colour of light into the

possible samur of a particular set «f prirnary colours by adding one o f the primary co1c)urs to the specimen

colour thric tsists outside of the grimut. In this case. the ratio of the primary colour added is reportcd as a

ncgarivc nurnber but nrgative numbers rire not practicril for rhe CIE'S colour notation system. I t \vas

nrcessriry tor the CIE to d e \ k the irnriginary primaries so that the negritive numbers do not appear in its

colour notation systèrn. The CIE Tristirnulus \'rilues are c;llc'ulated fiom thrce sets of data jG thaf

correspond to the rimounts of the thrrc. imaginriry primaries ris the cornponents of a colour. The data for the

imaginriry primaries rire callsd the CIE Culor-r~urtcliitlg Fitricriotis. ( .Agoston.G..4. L 987. pp.47-5s ) .

The rnosr significant point with the CIE (X. Y. 2) s y r m is that the luminance j7 is carrird solely by Y. so

S and % havc zero luminancc. This arrangement Ivorks for an sasit3r c;~IcuIation. Although [he values of X.

1'. and Z arc relati\.c. rin absolute valus \r.ith a unit crin be as igned to Y as the luminance of light thrit is

nicasurc'd dircctl). (rom the source. Luminance is quoted seprtrrirely tiom the tristirnulus values.

t :Igostcin.G.rl. 19S7. pp.47-58).

i o Xssumed tu b<i obtained through colorimctry. 5 7 1-uminrincc to light is lightness. value or brighrnrss to retlsctcd colour.

Cli,lours cjt'non-luniinoiis m:itcri:ilb c m bc alsr) specificd n i th the Clff' (X. Y. L) sFstcrn. T h e dit-ferencc of'

ttictrct-rcil r.oloiir from the c o l ~ ) u r o f light ib that in thc rne;lsurcnlcnt of mritcriai colours. mritrririls nccd t o bc

illumiri;itcd by ri light sourcc Lw colour mccisurenient and the l i @ being rncrisured is nc)t reccivcd dircctl)

Iloni the ~Ilumination wurc r . I'hc colour of' an opaque spccirnrn is mt.risurtid ris retlcctance and the colour

01' 3 tr;msp;Lrcnt spccinicn 13 nic;~wrcci ci3 rrmsrnittrincc. Thus the iofour of ri mritc'riril Jepends on rhc cuiour

qcctri im and thc lurninririit ot' the illuminritiim source. as \ v d I ri-; the rctlcction charricterist~cs and the

ribsc~rptiim charrictrristics of rhc material. The luminance of ri rnriterial can bc measurrd only in relation ro

the luminrince of the illumination source. The relative lurninmcr. rhar is, hnirio~is reflccrutzce of opaque

materials and I~urrirroils rrrinsi~iirr~tncr of transparent rnatzrirrls. rire crilled Oinrirrctnceficrors. The lurninaticr

hctor is dso rcprcsented by Y. and the type of illumination source. such as CIE ILL C, must bc mentionrd.

(:\gos;rtm.G..-\. 19S7. pp.47-5s). ( Figurrs 32-36).

Lct US revieiv the Ic~gic of the hlris\vrll Triangle and the CIE t S. Y. Z ) systern using the follo\ving

t;rrmulrie.

Suppose that an actual measurerncnt g i \es tigurss ri. b. c and d as fo1tou.s.

S : t a : Z = c i : b : c :ind luminancc (ur luminance r'rictor) Y = d

Thcn the CIE (S. j ' . Z ) CoIour Sotciticin cor a lurnincws apecirnrn \vil1 be esprcssrd uith a. b. c and d:

( S = 100 ri / b. Y = 100. Z = 100 c / b). luminrince d.

and ri non-luminous spccirnsn that is rneasured with CIE ILL C uil! be denoted in a similar \va'.:

( X = 100 ri / b. Y = 100. Z = 100 c / b). luminance factor d. CIE ILL C .

II'thc portions of X. J' and Z are rt.spcctivrly K. y and L. in the sum of'X i Y + S. thrn

' r : g : z = X : Y : Z and

s = X / ( X + Y + % ) y = Y / O i + l ' + % ) z = Z / ( X + Y + Z ) therefore.

x + y + z = l

:llso. X. Y and % are positive numbcrs. thzrdore.

:l pair oi \~alur.s .u and y introduced in the former paragrriph is calIed cliontc~ricir>+. and i t is expressrd ris (x .

y). (Apsron.G.A. 19S7. pp-49. 56). A chrornriticity notation systems with three parameters in a t\s.o-

dimmsi»nril spscr. such a s an equilatrr;11 triangk and the CIE (X. Y. Z ) is not convenient in practict.. and

tliis type of notation system rarcly uscd. but chromaticity notation systems only with t\vo prirametcrs have

fiiund ri bwad range ut- applicatim. The M r i s ~ ~ c I I Triangle crin be made usetbl by bcing ccunverted to a right

triringk \r ith x risis and y asis crcissing perpendicularly a1 the zero point tvhere blue is locrited (Figure 3 1 )..

This is thc basic frrirnc\vc)rk O!' the CIE chromriticiry diagram that is in frequent use today. (Agoston.G.A.

19S7. p.4S 1.

The CIE ( K . y. Y ) system has threc parameters in three-dimiinsional snace ro specify colours and is widely

xccptcd . Th13 .;jestem incorporates ttvo prirarnetrrs. .u and j.. fc)r chrornaticity (cornbined hue and

su r r i t i on ) nutation and one parameter. Y. for luminance (or value o r brightness) in a set.

As a more descriptive tvay to specit'y colour, the CIE (Ao. p,. Y) system designaies colour with the

do,riiiiciiir \ia\.ele,i,p,li jS (j.»). the e.vcirmio~l priry (or simply puriry. p,) and the I I ~ I I I ~ I ~ C I I I C L ' (or the

lrr~tirrtcittce/i~c-ior. Y ). O n the CIE Chromaticity Diriersm. the dominant wavelength is derermined as the

polni ivherc ri siraight linc from the rderencc point. passinp throuph the chromnticiry point of thc

5 5 In in~rruniental analyses such ris spectrophotornetry. the durninant tvaveIengh r e f rs to the wrivelen~th of

the main pcak. i ' l The plot OS ihc spccimcn on the chromaticity dirigrrim.

U> spcciriicn. hirs the specirum locus. T h e relkrrnce point is around the zero saturation point. either the

chrom:irii~ty point t i r the equril-cncrgy lizht or a chromririsity point for one of the CIE Sirindrird

~llurnin:int."~ The e.ucit;ition purit!! is the distance betivecsn the retkrcncc point and the specimen's

chrornaticity point a s rhc rritir) [ c i the distance betwesn the re fermce point and the bpcstrum locus rtt the

dominant \i,avelsngth. T h e illuminrint h r the rrfçrence point must associate the colour speçitïçation a s in

~ h c !i)llou mg c.urirnplc:

CIE 19-3 1 (i., = 603 nm. p, = 67.3 5 ( o r 0.673). Y = 0.20S). CIE ILL C.

It'thc Iinc rhat is extcndrd h m the r e f r e n c c point. passing beyond the chrornaticiry point. hits the purple

line. ihc cotour is a non-spectral colour. and its conpler r renr r r~ wcwelertgrlt is reportsd with 3 lettsr c

instead 01' the dominant wavelrngth thrit docs not exist in ri non-spectral colour. The cornplrrnentary

u~rivclc.n~rh is determincd ris the point ivhcrc the linè passin2 rhrough the rcfttrcncs poinr and the

chrornatiiiry point interccpts the spectrum locus. rts the line is extended towrird the opposi ts s idr of the

chrornaticiry point:

CIE 193 1 (2, = 496.5~ nrn. p, = 32.9 9 (or 0.329). Y = 0.336). CIE ILL C .

(Ays ton .G.A. 1987. pp.5S-6 1 1.

The CIE (S. Y. ZJ and the CIE (x . y. z ) are c a k d the colorrr ~iorcrrion and the CIE (.Y, y. Y ) is called the

cwlmrr spc.c.ificariori. Since thc CIE announced the recommendations o n its colour measurrrnent schernr in

193 1 rind 1964. the year of the recommcndation on which the schcrne is based is indicated d o n g with the

colour notatron rind the ccilour specitication. The notation and the specification brised o n the 193 1

rrcommendarion are expressed ris CIE 193 1 (X. Y, 2). CIE 193 1 (x, y, z), and CIE 193 1 (K. y. Y). T h e

nrmrion and the specification brised o n the 1963 recornrnrndrition rire expresscd ris CIE 1964 (Xia. Ylo.

CIE 196-1 ( .ulo. ylo. zlo) . and CIE 1963 (xlo. yio. Yi,,). The ycrtr 193 1 is ornitred u-hen there is no doubt

that the scheme is based o n the CIE 1931 recommendation. (Ag0ston.G.A. 1987. p.5S).

GO - The arc of the t o n p z shaped border. "' For exarnplc. the CIE ILL C o r the CIE ILL Dbj.

CIE ( I,*U*V*) and CIE (L*si*b*)

liilour> \ \ . i ih the sm-nc huc ii~und aluns (or riround) ri line rhat connccts the zero srituratir)n point and ri

point cm thc bordcr oK thc CIE 19-3 1 ( x . y ) Chrornaticity Dirigrrtm. Theorcrically. the saturaricm (chroma)

mua incrcrisc in an cqual step tiorn the zero saturation point to~vrird the border rrgrirdless of the hue:

ho\vc\.cr. an equril degrce of saturation dif'fercncs can rake diffcrcnt distances on the CIE 193 1 (s, y ,

Chrc~maticity Diagra~n. This problem is due IL) the non-uniform rissignmcnt of hues \vith relatively large

rireris tbr grrcn and grernish colours. The problem \vas diminished by the introduction of the CIE 1960 (u.

u) Chrc)rnriticity Dirigram and a rrvised version. the CIE 1976 (u'. v') Chromaticiry Diagram-

(.Agoston.G.A. 1987. pp.63-64). (Figure 25 ).

The CIE hris introduccd sevcrril colour specitic;ltion systcms as its c010ur theory hris bccn rcviscd. Agoston

summarises the histor?, of the CIE colour spccification systerns. 'The CIE 1960 (u , v) chromaticity

diriprn. \{.hich pro\.idt.s apprcnimately unitorm spacing in ri plane. presented ri starting point for the

Jcvelopmsnt of ri color sprice callcd CIE 1964 (U*VXW*) unihrm color sprice. The formula for calculating

color differences in this sprice. provisionally recommrndrd by rhe CIE. \vas used widely for over a decadr.

Thcn 3 modification of CIE 1964 (U"V*W*) color space \vas adopted. The modified color space is calicd

C/ELL'\' 1976 color- spclc-c and the formula thrit corresponds to it is rhe CIELUV 1976 color-diferrtzce

jhrwidrr (sornctirnes callcd the CIE 1976 ( ~ * i t * i . * ) fon,iulrr)."' The CIE 1976 (us . v ' ) chromaticity diagrarn.

rissocirited with CIELUV çolor space. was adopted at the same tirne." (Agoston,G.A. 1987. p. 107).

"To understand why a second color space. CIEWB 1976 colorsprrce. was also adopted. ive nerd to note

rlirii the color-diftt'crcncr torrnulri thar corresponds to it is a s~mplitied version of the ANLAB(J0) color-

difkrcnçs equarion that have bern adopted by scveri~l orpnisations and had becn in extensive use.

1,: Sec the section "Calculrition for the CIE Colour Systerns."

:\_iohti)n clplains the n c u CIE ic)lour h y ~ c n ~ s . "The basic 'rtructurcs of thc CIELU\' and CIELXB color

sprices are srmilar. In both. therc is a kxrticril rr~~rric ligl~r~tc*s_i L* (rilso called the CIE r /Y76/ li,plmwss

fhil~rio~i) iixis p r i s~ng ccntcilly rhrough cvcnly spaced horizmtal planes rhat rire subdividcd into square

grid, contriining coordinritcs lu'-. \.") (CIELU\') or ccmdinarçrs (3". b+) (CIEL:IU)." (.-\pston.G..-\. 19Si .

p. f 07).

The nietrrc.-lightness asis LF rcpresents l~rtclcss c-olor<rs. The risis passes through the horizontal plane. ( L I - .

\ . A ) or (a'. b+ ) . perpcndicularly r i i the plrinc rit each stsp of metric lightncss. The mstric lightness increrises

upux-dh trum black (Lm = 0). rlirc)ugh the neurrril greys. tu whitz (L* = 100). The hue rcgiuns o f ci

horizontril plane. (u*. v*) or (ri*, b*). cire sugesred roughly by the directions of the coordilurre cises: t u'

or i a" ibr rcds. i- v" or .t b" tiir y c l l o n ~ . - u" or - a" tor greens. and - v* or - b* for blues. The corrdares

o f perceivcd lightnrss. saruraiion and hue are. respecrively. the ~rirrr-ic l<~/mirss (L*). the rïlcrric clirortlct

t C"} and the nrc*tr-ic lrue arigie (If '). b a h in the CIELUV Colour Space and in the CIELAB Colour Space.

The value o f metrie chrcima (C*) is the radial distance from the metric-li~htness axis [ci the ploc of the

spccimen in the COI OU^ space. Thc metric hue angle (H') is rhc cingle mecisurcd be tnwn the rnetric-chroma

radius of the spccimen and the pc)sitive part of the u" axis (CIELUV Cdour Space) or ri" m i s (CIELAB

C o l w r Spact.). Xlztris hue angle (I-iC) is e~pressed on ri scrile tiom O5 10 360°. measured counterclockwise.

C o l w r ccwrdinrites (u*. v * ) and (a". b r ) are calculrited using the CIE Tristimulus Values (X. Y. z ) . ~

(.-\yston.G..-\. 19S7. pp. 107- 1 121. (Figures 37-10).

For any givzn colour. the numerical values of metric chroma (C*) anci metric hue ansle ( H G ) in the

CIEI-UV CoIour Spact' arc generrilly difkrent (rom the values of tiicir countzrparts in ihc CIELAB Colour

0 I Scc ~ h c scction "C:ilcularion b r the CIE Colour Systems." r r l Scc the scction "Calculrition t;)r rhe CIE Colour Systèrns."

Calcufrition for the CIE Colour Systems

f icre. thc CIELLA: 1976 Ccdour-dif 'frcncc Formula and the CIELAB 1976 Co lwr -d i fk r ence Formula are

presenrcd. ( :!zostc~n.G..A. 19S7. pp.240-243 1.

B y the drt?nitic)n of the CIE Chromricicity (x. y).

s = S / ( X t \ r '+Z) y = Y / ( X t Y +Z) thersfors.

x = x k ' / y Z = ( 1 - x - y ) Y / y <2>

T h e CIE 1960 Chromriticiry (u. v ) and the CIE 1976 Chromaticity (u'. v') ( the latter is the CIELUV

Coordinrirt.j) are calculated eithcr with the CIE Tristimulus Vaiuss (X. Y. Z ) o r wirh the CIE (K. y. Y)

C d o u r Spwi ticrition:

u = u ' = 4 X / i X + l S Y + 3 Z ) = J x / ( 1 2 y - 2 ~ + 3 ) <3>

L = G \ i P / ( S t 15Y + - 3 % ) = 6 ~ / ( 1 3 y - Z ~ + 3 ) c4>

L ' = o \ i ' I ( S + ISY + 3 Z ) = 9 y / ( 1 2 y - 2 ~ + 3 ) <5>

f-ron~ tiirrt~ul;ic. c1> and <2>. thc diflkrcnce hc.t\vcc.n the C I E 1960 Chrnmariciry (u. v) and the CIE 1976

'I'hc. CIEL.-\B Coc)rdinritc.b ( ri", h':) rire calcullitttd \vith the CIE Trisrimulus \'rtlur.s of the specimen t S. j' .

Z I and [hi. C IE Tristimulus \~rtlues of the rel'erence white (.&. Yo. 20):

a" = 300 ( ( X / .&)':j - ( Y / yo)[;; ) <6>

b1 = 300 ( O * / j',,)"' - < Z / z,,"' , c7>

Ft)rrnril:i CO> 15 \.alid onl>. \vht.n S / X,, . Y / j', ;ind Z / -& d l s s cecd 0.01. If Y / Y,, = 0.01, then L* =

S.99 14. :inci hlunselj's Vrilutl \.' = 0.9. ripprinimatzly. Also, the referencr: white is usuaily sonsiderrd [ci be

LI perkct dit'iuscr that rcf lrcts ai1 light recsived at irs surface. therefore. Y. = 100.

In 1959. rhc CIE recommt.ndsd rhat rstlectrtnce measursmttnts should be related to a perfectly rctlecring.

pertectly d i f f u i n g surface. Srncikcd mrignesium os ide (iMgO) has besn used tbr this purposs. T h e spectral

rctlccrrinx of the ~ u r c a i e o f s m c k e d rnrtgnesium oxide can rerich a s high a s 9s CG. Some o th r r highly

retlrctive materials rire also used ris \{.orking standards for nt ' lectance rneasurement: presssd magnesium

c~xide d iA. pain[ o r pressed pcnvder of barium sulphrite (BrtSOJj. mrigncsium carbonate (MgCO;) b lwk .

glrtzed ct--rrtrnic tile, and vitroiitc. glrtss. (Wyszecki.G.. t t f al. 1967. pp. 180- 1 Sb).

The colour differenct. benceen two colours can be calculated with either of the two formulae recomrnended

b> the CIE. utilising either the C I E L U V Coordinates (u*. vz) o r the CIELAB Coordinrires (a*. b*). with the

iIluminant identitled in the record.

Thc CIELUV 1976 Colour-ditfkrcncc Formula is

AE ( L U V ) = ( (AL*)' + (AU*)' + (AV*)' ) I r ,

\\iicrc ALx, AuT and Av" represznt the differcnces of L*. u" and v*, rcspectively. berween thc two colours.

and

3. 1.3. Iniportant Conccpts in Colour Theory

Iluc. l 'duc, and Chroma

H u c mean'; the rictual '*colour'- ;ha[ ~ v c l JCX ( r d . yeIlo\v. C t i . ). c.4goston.G.A. 1987. pp. 12- 13)

(Levko\\~rz.tI. 1997. p .6 ) . For exrimplr. in an eupression "a dark. pinkish red applc.." the phrase "pinkish

r d ' nominrites the hue of the ripple.

'The term value \vas tïrst used by MunseIl in the Muriscl1 Book of Color system. It refers to the relative

drirkness or liphtness of the color. in the MunsslI system" (Levk0witz.H. 1997. p.7). What MunselI calls

\ d u c 15 also cri1lrd intensity. lightncss o r brightness. These trrms r e k r to the amount of achromatic light

emirted or rctlected by the objrçt. Valus is ofien described as how much black is mixed in the c01our.'~

"The rcrrn i l l t c ~ ~ s i e refèrs to achromatic colors. The term liylitriess rct'rrs ro objects. and is associated with

(1 ' hlorc preciscly. "tvfiich drirkness (or brightness) o t y c y corresponds to the d;irkncss (or brightnsss) of the coloi~r."

rctlt.ctd Iighr. \'crbril degrecs li)r I~ghtnsss are very Iight. Iight. medium. dark. ver! dark" t Levkinvitz.H.

1997. p.7 r. The rcrrn Dr~.~l,rnc.s.\ ih uwd t i ~ r l i ~ h t sources. and is associaird with emitrcd light thrit crin be

ver' diin. dini. rncdiurn. btight. o r ver), bright. (Agostcin.G..-1. 19S7. p. 13) (Levkotritz.H. 1997. p.7).

Chromci and ssturrition r e k r IO the purity of the colour ris ri mixture of ri hue and an cichromatic colour

(ii hiic. g r q . o r blrick). In otht'r ~vords. thc Icbs grry the colour has. the more chroma thc colour has. and the

morc h3iur3tcJ ~hc. colt)ur is. "Strrltrcirion is colc~riutness rsl;itiw to the color's lightness while clirorrrcr is

colorfulncss comprired ro tuhite. When lightnrss changes ri change in saturation is perceived. Increrised

1ightnc.s~ causes 3 perceived drcressed saturation. and vice versri" (Levkowirz.H. 1997. p.?). Saturation is

csprcsscd 3s grcyish. moderate. strong. o r vivid. Chrtmta is associated more closrly tvith the .Munsr.ll

s'hrcrn. anci doeb not change tvith lighrncss. ( . - \go~ton.G.~l . 14- 16) (Lrvkmvitz.H. 1997. p.7).

3Iising Colours

XI i s in~ w l ~ ~ u r c x i lights to crcarr. a hue is called c;tidirrt.c rrtrxrrrw and rnixing colorants (coloured substances

such ri3 pigments) is crilled sithrrtrcrii.~ ntirrrtrc. In both cases. the resultrint colour is Iess sriturrited than the

ortsinal colours becriusr the resultant colour sprctrurn is the average betivren the spectra of the orisinril

coic)urs. and ultimritcly. becomss thrit of hueless light sources (o r objecrs) that cmit (o r rrtlecr) lighr through

thc visible range in nearly equal rimounts. (Apston.G.A. 19S7. pp.41-45) !Grrritscn.F. 1983. pp.71-129).

On the clne hrind. it is crilled additive colour mixture when colours are rnixed by superirnposing lisht berims

trith ditfcrent cr>lours. bscause the luminance of light incrcrtses ris ri result of mixing. and the colour

bcc.i)mcs mort. u.hitish. This crin be visurtlised tvhen ttvo spotlights rire suprrimposed on a whire surface.

Thc luminrince increases whcre the two iight beams collidc. because ihe two Light berims' energy per rireri is

xicied tugcthcr. O n the other hand. it is called subtractive mixture whcn colours arc mixed by

superirnposing Iaycrs of transparent mriteririls trith differcnt colours. bccausc the lightness (o r value o r

brighincss) is reduced a s ri resuli of mixing. and the colour approachss black. This crin be visurilisrd tvhcn

\Vhen c ' ~ A x m t s such ris dyes o r pisments are mixed. each co lonn t absorbs the incident light (illurninriition)

indrpcndcntly. but ri portion o f lisht that is trrinsmittsd through a layer of colorant m a i be scatterrd by

rtncither Iriyr'r of colorant. Thercfim. in such rt case. regardle33 of the t'rict thrit rnixins colorants is often

rrrfkrrcd to as a subtractii.r proccss. i t cannot hc rissumeci thrtr misrd colorrints aI\vays produce a c d o u r \rith

rt subtrrtcrrvc mechanism. (Nassau.K. 1993. pS53).

The hue sa inrd (rom additive, subtrrictii.r: or rotary colour rnisturc appears sorncwherc. bet\s.ecn the original

c o l ~ ~ u r s on the rainbow colour spcclrum o r on the colour srrclr (Table 6) . The location of the product colour

t)n thc colour spectrum or on the colour circlr correspond3 tc) the ratio of the original colours. When

iornplc:mr.n~ary colciurs arc mixzd. ri huclcss coluur is pruduced. \irhcthtx rhc resultrint hueless colour is

\\ hite. \.artous shades of g r q . o r black. depends on the ccirrrcr of the colours (lizht or materid) and the

Iightncss ot' thc original colours (Tabfc 6 ) . The colour prociuced by mixing can bc inferred by using the

chromaticity diagram.M Whcn the line thrit connects two orifmal colours is dividcd into the ratio of t h e

misrure in a chromriticity diagram, the location of the dividin: point ripproximritcs the hue and saturation of

thc produit of thc mixture. (Agosron.G.A. 1987) (Gerritsen-F. 19S3. pp.7 1-1 25)) (Judd.D.B.. et aI. 1963.

pp-6 1-7 1 ).

:l coltwr i i r i l ~ . also crillecf ri c o l w r \vhc.rl. ih ri :rimut of ciA)urs arrangeci in a circle accord in2 to certain

rulcs. 1 ' 1 1 ~ genesis of thc dc;i 1;)r c o l ~ ~ u r cir i le> siin br: diitr'd brick to chat o f Xeivton ( 1600). In ri c d o u r

ï~rc l t . . c01~)urs may be alrgnt-cf in the hue ordcr c~t ' the r a i n b w . in ri gradation o f saturation u i t h the sarnr

hue. or IL) sho\v the rtilrition~hip rimong primary 4 o u r s ancl c~~mplemen ta ry colours. it seems to b r ri

niodcrn prrtcticr: ro I ~ r i t e pu rp !~ . ri non-spcïtrril so lour thrir ci~1c.s not ripperir in the rainbou.. bet\vr.cn red

and blur \vhrn colours art- alignsd in the order cif the rriinbcni.. The ordzr hues appear in the rainbow is the

order or rhe dominant ivavslrngrh of light. As ivrll. purplc is located bctween red and blue i n t h e CiE's

chrornaticity dirigram. o r the CIE 193 1 c x. y ) colour dirigram. althoush the chromriticity d iagram is not in a

n ) u n J shript.. (Agoston.G.X. 19S7. pp.45. 56.67) (Gerriuen-F. 19S3. pp.21. S3-93) (Wilcus.M. 1994.

pp.31-1 19).

t'rirnrir? colours. or sirnpl). prirnrirIcs. i?; ii term thrit wnveyo; an image of bright. strong co lours but the i w r d

prirnrtry c~ i lou r s can be d e ~ i n e d more ttxhnicrilly. basic rt-quiremrnt o f r i set of three primaries is thrit no

combination of any t ivo ut' thcrn mritcheb the rhird. To have particulrir utility. the qualifiçrition is usually

ridded thrit the rhree primaries be selected s o rhar the grimut of colors obtained by mixing [hem includrs al1

hues and is ris Iargc as i > practical" (.Agoston.G..-l\. 19S7. pp.44). Primriry colours rire not ri prtrticulrir set o f

colours but can be riny set ot 'colours char sa;istit-s the requirsments of prirnriry colours. T h e r e a r e t\vo types

o f primary colours: ccc/dirli.e prir~inries and sirbrr-trcrii.e pr i t~zt f r i~ '~ . Red, green and blue (violet-blue) function

a s prirnriry colours when coloursd lights a r e mixed (additive mixture), hence they rire called the additive

primaries. Cyan (slightly greenish biue). rnrrgcnra (purplish red) and yellow function a s primary colours

\vhen colorants are mixed csubtrrictive mixture). h rnce the? rire ctilled the subtrricrive primariss. Additive

primarit.'; a re fouiid ivhere s RGB r~iodel colour systrm is employed to produce colours o r t o record colours.

fiir exrimple. un ri te!evi'iic>n rnonitor. Sub t rx t i ve primaries rire found typically in ri colour printing process

~vhc rc ;i C:\I 1' rrrotld colour systrm is u s d to producc colours. Under c u r e n t tcchnology. the RGB models

in practrcril use iire not capable of producin: al1 colours that crin bc perceived by humans. nor a r e capable

\\'ilrit :\ffccts thc Appeürancc of Colour

Ttic coltrtrr..; 01' rhz surn)unding tnvironmenr ;rtbEcr the appearrincc of the colour that is being observrd. This

13 \vhy the specimen must be tsolatcd in ri neutrril srey background or in total darknrss. The type of

illurnrnriticin. 01'cuursc. crin change the colour of a material by intlucncing the colour spectrum of the

rctlectitm rind the t luoresxnce (Figures 32-30) . Human vision sensitivity itsc-If changes depending on the

illumination lype and the condifions of ~ h e light sensors in rhc eyt. that adapt to the illumination conditions.

:! judipnent on colour LI[ t\vilight is espt'cially unreiiable. cX~oston,G.A. 1987. pp. 1 1-12.31-35)

tGerritsen.F. 19S3. pp.2S-35) tJohnstun.R.iC1. Pigruetir HairtilmoX- v. 3. 1973) (Judd.D,B.. st al. 1963. pp.11-

12 ,.

hfctamcrism

\Ictrirncri~rn ih rspc.rienccd in daily liic: tvhen colours rire matchrd (idcntified ris the same colour) rind when

cr~lours arc coordinatcd in hrirmony. hlztrtrnerisrn is ri phenornenon in the science of colorimctry

(lolinston.R.M. Pi.qmcr~r HmuilrooX- v.3. 1973. p.244). The ulrirnare p r o b k m of rnetamerism is that the

colour ot'onr material appears difSerentIy under differrnt conditions. The technical definition of

metamcrism. houvvrr, rilso difîkrs depending on the purpose of the use o f colour.

First ot'afl. a prirticular colour sensation in the humrin vision system can be induced by colours with

dit'lkrcnt spectrril power distribution. For example. several green specimt.ns rnay appcar ta have the same

Srwn colour t o onc perscm but the spccirnens may show different colour retlectrince curves in

\pcctrolihi,iomcir). Excçpt for a nionochrornaiis colour." the perceivsd colour is a result ofavenging in

thc c~,Iour nli*ture ( :~~o?;ron.Cr.:l. l9S7. pp.43-44) iGerrirsen.F. 1953. pp.7 1-82). DitSCrcnt colour mixtures

ï:in ;ippc;~r tu h:t\c the bamc c d o u r bccriuhc the humcin c ~ c icinnot idcntify the wavclength composition of

light u-hcreah the car d o c ~ dc'tcct cach of the musical tonçs in ci chord. .A set of stimuli (causes of colours)

thrit c;:use the same visual senscirion regardless of their di t'ferent colour spectrri is called a nt~rc~ni~ric- sel.

Thc \tirriult in the brime mctameric set arc callcci rrrcrturrcr-s. N'hm colours ot'priint are matchcd visually. the

\.ihion sriniuli rire mritched but ncit necesstirily rhs priints. becciuse the colour spectra o f the pains may be

dit'krcnt. (Xgoston.G.A. 1987. pp.40-4 1 ).

Second. the causes of metrimerism must be considcred. Illwr~irlclnr rrterccrneristn occurs when the srtme

colour 1'; vic\vcd under illurninanrs ~vith diffrrent colour specrra. for rxample in daylight or undcr a

tungswn Irimp. Even ~vhen the property of the c~~lorrint is unchangsd, the colour spectrum of the light

rctlcctcd by the material changes in relation to the incident lisht or illumination. (Figure 41). Another cause

or' illuminrint mctrimrrism involves the tluorescence of the materilil. Sunlight contains a signiticant Ievel of

'~hort ii-rivslcngtli Iighr. in other words. ultravidet ligh[ and blue lighr. thai escires the material to tluuresce.

whcreas an inccindescsnt illumincirion source daes not contriin short wavelength lights rit sufticisnt levcl to

induce ;i strong fluorescence in the material. If a material consists of ri driylight fluorescmt colorant or

tluormxnt brightcner (apical brightcner). the colour of the material \vil1 exhibit an obvious dit'firznce

undcr diiferent illuminations. (Nrissau.K. 1993. pp.854-855 J .

O I ~ C I I - C ~ I ) I C ~ ~ U ~ I P ~ I S I ~ I occurs as 3 rlsult of the different visual sensitivities among psople with "normal"

(Nassriu.K. 1993. pp.854) colour vision. The variation in cons " concentrririon and conr distribution results

in the diftkrcncr. of the visual ficlcf size. and Icads tu the difierence in the eye's scnsiriviry to colours. The

eftkcr of the field size on colour sensitivity is retlecied in the differencr brisreen the CIE 1931 Z OSraridc~rd

-- -

0 7 :\ ~pcctral colour or colour thar consisis ot'a single wavelen~th band (Agoston.G.A. 19%').

03 t\ co10ur bensing orgrin in rhc human eyc. (Agoston,G.A. I9S7) (Gerritsen.F. 19S3) (Judd.D.B.. et al.

1963). t Lcvko\vitt.Ii. 1997) ( Wyszecki.G.. et al. 1967).

I'hird. disagreement in tcrrninology cxists. lohnsron suggests thrit the term geometric rnetarnzrisrn shcwld

bc abolished becriuse this phenornenon entails an artribure o f thc appearance other than cotour. .A more

speci tk nu rd ~ortior~~c.rercl~rot~t(~~is~tr has been s u ~ g t s e d insterid although Johnston considers thrit the term

13 ioo Ions t i r mcist people except f,r purists. The jargon itrsrr-urrierirtrl ttrercotierist~i also rrceives an

objection trom Johnston. T h e t r rm indicarcs that ri pair o f trisrimulus çolorimetrr s have difierent spectrrit

r q x m s r chrirricrcristic~. This is rrither a technical issue than ri phenornenon o f meturnerism. I Johnston.R.h.1.

Piyrtwtr H<rrrdhok 1.. 3. 1973. p p 2 U - 2 4 6 ) .

Agc>ston argues that \\.hite light u-ith various spectral distriburions can bz mctamers becriuse a piece of

uhite priper appsars similrirly white under diffcrrnt white illumination (Agoston.G..A. 1957. pl 1 ). Johnston

rilso conbiders the pvssibrlity that some different types of illurninririon are mctarneric. (Johnston.R.~M.

P~yttietir lfcrridbook i e . 3 . 1973. pp.311-746). This issue. ho\vevt.r. may nerd a furthcr considerririon in some

cases. Thc human s y e is capable o f adripting to illumination n i t h different colour spectra. thus sensing ri

colour as the same under differrnl types of illumination (Gcrritsen-F. 1983. pp.53-54). The colours

percei tui under different illuminririon conditions crinnot be compared side by side. to besin with. In such

cases. i t may not be appropriarc to reiér to rnetamcrism ~ v h e n dzscribing chc sirnilarity in the perccived

colours under different types of illumination.

Finally. the description 01' metamerism is not riIivays scicnritïc enough. The "*degrec o f mctarnerism"

t Johnston.R.M. f'i,qttrcvlr f /~~t ic/ /woX. v.3. 1973. p.246) correspunds to the cxtcnt o f l h e diffcrcncr in the

?rpcctr;i o f the stimulus. Phrases such a s "sciwsly rneramr=ric" (Johnston.R.M. Pi.qr~tcrr! fIct1lrit5ook v.3.

Light ris ari Elcctromagneiiç Phenonicnon

Toda~. . n s knout thrit \vc necd Iight to >cc. Ltghr is creared in :t luniinou-, body. such as sun. tÏrè o r 3 light

bulb. irrailiared ti-om the luminous body to objects. retlected tiom the objecr surfrices. reccived by the eye

which is a light sensor of human o r animal. and the objects are perceived. Vision as ri physicai phenomenon

is a passive activity t'or human. although people can selrct \\.ha[ thry want to see. In older days. howevrr.

\ . i~ ion \\.as not a l \ v a ~ s regardcd as an passive astivity. Somc people thousht that objects emitted rays that

induccd perception in the q e . some people thought that a raj. \vas ernirted tiom thc eye to scan objects. and

thc ottiers believed thrit the \vorld is tilled tvith an invisible ';ubstrince that mediates visual activity between

the objt'cts and thc ejre. (Grrritscn-F. l9S3. pp. 13- 1s).

Lisht actuall! is a form ofencrgy thar can 1raw1 \vithout a help of a medium. in contrasr to some other

hvms ot'rnergy. such as a n oct.ari \vavt. thrit totally relies on the esistcnce of medium. \vater. to travet.

1-isht is clr.crromrignctic radiation just as radio uaves and S-rayh arc. Lisht consists of photon particles that

1 1 0 ~ in a bcarn \\.hile vibraring in a ccrrriin tu\-clzngth and t'requency. In a vacuum. or a hollo\v spacr

ivithout air, light and other kinds of eltsctrornagnctic nave trrivef rit a constant spccd. 2.993 x 10" rneter per

sccond (or 1 S6.500 miles pcr second). T h e dimension and the speed o f vibration are considercd to be

constant unless the radiation rccei\,cs a speciril treritrnent. U'avelength is the distance thrit light procrrds

during onc cycle of its vibration. Frequency i> the number ot' vibrations chat occur in a unit tirne period. The

specd. wavelength and tiequency ot'a electromrigetic radiation crin be represented by c. i, (lambda) and v

( r iu ) respccrivcly. and rhey have a very simple mathematical rclationship:

C' = L%

Iir;i\,clcngth and trcquency arc rcciprocril hecm~st. thc rnathernritical prtrducr of thcm is consrmt. The unit

t i r \{,a\ clength crin bc :i (:ing..irriirn. 10.'" ni 1. nrri ( I 0" m 1. cni. rn or even km. Frcqucncy is cspressrd in

tcrrnh of tiz (hcrtt , cycle pcr - s ~ ~ i , n d ) that is rils~j exprcsscd as s" (reciprocal second). (r1~0ston.G.A. 1937.

pp. 17-2 1 ) (Hu.ihimi.K.. et 31. 19S3. pp. 106. 2391 t Judd.D.B.. et al. 1963. p.2S-29) (Skoc)_«.D.:\.. ri al. 199s.

pp.1 17-1 19).

'I'hc rirnount (quantum) of cncrgy ~)t'rlcc~rc)rnrignc'tic radiiiticm rncluding light is funetional to its frequency

accorciing to Eitlsrciri 'r qunriot i :

E = ir LI

E is the rimount ot'enrrgy. ii 1s P i m k ' s ccrtrsrrr~ir (6.626 x 10.'' Js ) and v (nu) is the frequençy of the

radiaticin. I-Iencc the higher the ticquency. the higher rhc radiation cnergy. In othrr words. the shorttx the

\\atc.lcngrh the hrghcr the rcldiviirm eiir'rg,'-!'. (-\I;irrindiII.hl.G. I9SS) (Sh,g.D..A.. sr al. 199s. p.130)

c \'oedisch.R.l!. Pigriretir f/citidl)ook v. 1 . 1973 i.

Elecrri~mrignetic \caves betivccn 3SO nm and 6SOnm (or JO0 nm and 700 nm. depending on the context) are

criilcd vibibIe light because the light in this region stimulatcs the human vision systrm. The colour of Iight

chringes riorn violet t h r o u ~ h bluç. green. yellow.. orrings to red as the \vrivcl<=ngth becornes longer. Visible

light is n,;: :il\vriys soloursd. The light that causes visual sensation but docs not have a colour is called rcflire

li,q/ir. \\'hite lighi is nut a particular type of lighr in terms of the colour spcctrurn. Driylight. one of the most

comrnon ~vhite lights. \\,heihcr the direct sunlight or the light from a cloudy sky. covers the entire visible

\vavt.lcngth range rrither evenly. In contrasr to daylight. sornr artificial white lights. such as the light from a

rungsten-tilamcnr Iarnp and the light t iom ri tluorescent famp. have unique. uneven specrrri containing

dit'fercnt colours ln diftzrent rritic~s. A s such. light nith an unevrn spectrum does not always induce colour

perception, and thc reason t'or this is rittributcd ~o the human eye's adaptation to the ambient lighting

conditions. (Agosron.G.A. 1987. pp.67. 72-73) (Gcrritsen.F. 1933. pp.53-53).

'I'ransniission, Absorption, Heflçction, and Fluorescence

R'hrn light passes through a transparent matcrial. the energ? of the light is partially absorbed by the

rnriterial and the resr is rransmittcd. Tht: ratio of the light e n q y that exits the material a s a result of

rrrinsniission is crilcuIated as rluristtrirrtrticc:

T = P, / P,,

7' 15 the transmitrance. PL, is the po\vcr of the incidcnf lighr. and Pl is the potver o f thc transmittsd lighr. The

pc'rccntlige o f the rran';mittrince is cltien used:

T = 100 Pl / P,, Ci

The miount of light ribs1)rbt.d is glven as C J ~ S U ~ ~ C ~ I I C L ' . A :

.-\ = - log1,, T = llig,o P u / P ,

.-!b.sorbancc dcpcnds o n rhc prith Icngth (6 ) and rhc cnncrntrririon of the ribsurbins rnsterirrl (cl- Bu Becr'r

Ilri:.. the ~ i b s o r p t r \ . r ~ ( n ) is obtri ind (rom rhr f o l l o ~ v i n ~ torrnulrie (Skoog.D.,A.. et al. 199s. p. 139):

. - \ = U ~ C o r u = . 4 / U c

Rt$ccrrcm is an abrupt change in the direction of light propagation at an interface bcnvern t\vo different

m:ttertal~. Reflsctmn rnriy be qxcular or diffuse. Specrtlm rrflccriori occ::rs o n srnooth surfaces. such ris the

burfaceh of rnirrors o r highly polishcd metal surfaccs. Specular retlection enablcs humans to perceive a

hcirp irnrigc o f the light source on the &jeci surface. Diff i isc rcflecriori. o r rccirreririg. cxcurs o n rough

mfrices. wch ris thc surtaces of logged &w. After being rellzcred diffuscly. the incident light does not

forrn an image ol'thc lizhi source bu1 the image o f the dift'usely reflecting surl ice cari bc seen- The amount

o i ligtir rerlccrcd in reI;ttlon [O the amounr of'thr' incident licht crin be txpr rssed in t\vo different mrtnners ri,\

r c y l c ~ c m l l '.cv:

',.; K = 1 00 P, / P,, 5 t)r

K = - loglo P , / P , ,

R is retlectance. Pr is the ratio of the potver of' light retlected and Po is the poiver of the incident Iight.

f \Vc~k .> l . I~ l . 1997).

Some substances not only rransrnit. absorb and reflect elrctromrignetic radiation inctuding light. but they

&O rr-ernit the absorbed energ! as rircrromrignrtic radiation. T h e re-cmitted e l ec t ro rna~ne t i c wrive is

id lèd Iumint.scenct.. phosphoresccnce, and tluorrscencr- T h e mt-çhrinism that causes luminescence.

pho';phorcsccnc<3, and tluorrsctmcr. is discussed in ri dedicatcid sccrion in the "Theory and hisrory of'

D a ~ l i g h t Fluorescent Pigments."

What is Colour?

The tirsr 2nsu.t.r ol' Aguston to this questicin comcs from E\.ans. 'The c d o r riuthority R.M. Evans ( 1905-

1974 J pointrd out thrit the \vord Colo~tt- 'ris i t 1s uscd in ordinriry speech . . . has man!, dit'tcrent meaningh.'

Even in the scientitic domains ol'chemistry. physics. and ps!~chologj~ i t has dit'ferent specializcd

rneaningb." (Agostun.G.A. 1987. p.5).

: l p s t o n ccinsidcrs. "an cveryday usage c ~ f the \vord color. ri uhrige that impliss the concept that color is a

propcr t~ . o~'ttttrr~r-iuls." jus[ ris "ri ripe tomarc) hris the properry of being red." Then Agoston thinks about

cofoured lisht. Colour i'; "a pl-opcrzy o/lit~ltr." tlirrefore. a red colour is irrridiaisd to us from a rrd traftic

lipht. Thesr rire thc pre\.ailing concepts of colour. nonetheless. both are dismissed in Agoston's theory.

"The concepts o i color ris a prciperty of materials and of lighr s m r c numerous practical needs in driily l i t .

the most important of \{.hich art. thosr of survivril. The concepts serve \ r d i in a host of ways in commerce.

art. science. and tcchnology. For thess r a sons . it cornes as a surprise to many people that these concepts

are iricor/ucr. Perceivrd color is incorrectly givsn as ri propsrty of marcrials and ris ri property o f light.

Yctvton. discussing thc subject of light in his book Oprich ( 170-1). srrtred corrsctIy. 'Indecd, rays. propal) .

t.xprèsst.d. rire no[ colored'." (Al1 quotes in this paragrziph are from .Agoston.G..A. 1987. p.5).

Agoston defends his theory with an rinalogy. "Another cxample of an incorrect concept that serves us well

in daily l i f is the idea thrti the sun rises and sets every day" i.4gosron.G.A. 1987. p.5). Actually. the Sun is

staticinriry in thc s d a r s'stem and the earth revolves riround the sun. \vhile spinning around on the asis of its

o\m. thus crcating a dynamic landscape with the moving sun for the people on eanh. Sunrise and sunset are

p m s of this dynrirniç lie\\. of the Sun. bur thry arc not the dynamics of the sun itseIf. Agoston admirs rhar

thc'se "inciirrect" (:\gl~ston.G..k 19S7. p.5) notions \vil1 crmtinue t o serve to us in rnriny important ways:

criIour is a property of materials and of light; the sun riscs and sets evcry day. Regrirdlsss nt'lhis convenicnt

Psychological definitiims o f co lour is a l so important to Agost~)n"> ~ t u d y .

"The p3ychc)logisr L.,M. Fiurvich poses this question in his book. 1-ft. a A s whe ther an object hris co lo r bccriuse of its phpical-chernical rntikeup o r whether illuminrition const i tutes the c o l o r of the object. Continuing. h e asks whether c o l o r is a photochernical event in the rrtina. ri neural brain-excitation process. C r ri ps).chical èvent. His ansii-er is. 'Color is al1 thes r things . ...' but h e a d d s thrit. before esplor in- these ti,prcs. 'the main point to be m a d e is that Our perception o r ' i o l o r ordinririly d r r i v e s tCom a n interaction bciiveen ph),sical Iight r q f s a n d the visual system o f the lii.in2 organism. Bo[h a r e involved in sceing objccts and perceiving color'." (Xgoston.G.A. 19S7. pp.S-9).

Xgoston quo tss Kuchni 's discussiim o n phys icd . physiotogical. psychologiccil. a n d psychophysical aspects

speaking .I 11t>\\,cr ot 'our brriin activiry." Kuehni 's "circulrir*- Jct lni t ion o f co lour Lur s c i e n t i t k use is quotzd

h). A ~ c ) s t ~ ) n b c c r i u x i t coni.e>.s ri related psychologicril mcrintng. "Percrived c o l o r is the rittribute of visual

perceprion thrit can b e descr ibcd ty co lor narnes: White. Gra). Black. ï e l l o i v . O r a n s e , Bro\vn. Red. Green.

Blue. Purple. a n d si) o n by combinat ion5 o f such namcs." Hurvich is a l su quo tcd b y Agoston. "Any atternpt

to rirri\.t' LI[ a detinition ot' the \vurd involves o n e at o n c e in riIl rhc comples i t i e s o f vision." (A11 quotes in

this paragrciph a re f rom Agoston.G.A. 1987. pp.8-9).

As ri practical definition o f co lour in t e c h n o l o g . Agoston ';tates that co lour is t h e character is t ic o f light that

is recogntscd b>. humans rhrough ti sensat ion in the brain \ \ .hm the l isht is perceivcd. Agus ton notes rhat

colour is not ri sensririon. (Agoston.G.A. l9S7 . pp.9- IO).

O'P Eithcr the prcipcrty af a materiai o r the propcrry of lighr. 7 0 J o h n s t m (Jolinston.R.M. P i , q ~ t ~ l r H m d / x ~ o k 1 s . 3 . 1973) suggcsts that the use of t h e ivord mctamzrisrn should b c Ilmitcd tc) the crise in ivhich [wu colours. that have difkrcr i t re t lectancc spccira \ rhen rncasurzd ivith a spectrophotometcr o r ri s i m i l x insrrumcnt. appear IO rnritch under particultir condition';. Johnston is opposed to rctki.ring tc) rnctrirnerisrn tvhcn the colour o f one object rippcars to c h a n g e undcr diffcrent conditions.

"191r. 1 2 1 \ . 5 . ro .$peuk pro p.^-1.1.. < I ~ - L , r i o r r . ~ l ~ ~ t ~ - e d . I I I ~lir'trr ili~,rL* is 1lor11Ï11.q d s r tl~ari « crrr~iiri. Po\i.er trilcl Disposirrlirr ro srir ~ i p a Scristrrioli u f r l i i~ n t - rlitrr Colour-. (.I'c,ii-turr lif'c01r-04). pp 12-1-122.)" Then he poses qucsricms and rins\vers about colour. "Ii'hat is co lor? 1s i r a property of rhe objecr that we scr? 1s it a pruperry o f our visual systcm'? Of Light? . . .. I t is all of the above. Color is our perception. our response t o thc combination of light. objccr. and obser\.er. Rernove eithrr one. and rhrre is n o perception o f color. Tha t nicans rnar in ordsr to fully usc cr)lor. Lve have 10 understand al1 of these. . . . . And Lve have to rnake su re rhat \ . i ~ ~ a l rcchno1ogir.s thrit u.c devclop a r c rnrirched rt) the human risuril caprtbilities." (Levko\vitz.H. 1997. p - 3 1.

.According to the E I I C ~ C ~ U ~ C ~ ~ ( I of C I I L ' I I ~ ~ C ~ I ~ T ~ ~ I I O ~ O K J (Srissau.);. 1993. p.S-lI ). "color is the part o f

pctrccption char is carried to the eyt: tium our surroundings by Jifferences in the wavelengths o f light." Th i s

in\x)lvcs thc spccrrril po\vcr disiributkm and rhe type of thc [ight tlom the illumination source. and the

interaction hctn.cen illumination and the rnatrcr. ti>r instance. ab~orpt ion . reflection. refrriction. diffraction.

su t te r ing . and tluorcscence. I r rilsc? in\.ol\.ss the biological perception systern including the eyr . the

infcwmatim prirh tiom eyc to brciin. and brriin thrit processes the final interprrtrition. (Nrissriu,K. 1993.

p.S-il). Sa.isciu cites tifieen causes r>fcolour in live caregories; \vith esarnplcs. (hrrissau,K. 1993. p.SGl).

(Table 7 ) .

71 - I'hib expression hrts been alreridy quoted as Hurvich's tvord in the tbrmcr paragraph.

Colour Measurement

('olorir 13 :t p ~ y c h o l o y c a l phcnorncnon t i r human bcinss. The human cyc. a c d o u r senmr \vith sensiti\fity

liigfil~, spc;iflc [O cach perscm r c c c i ~ c . ~ light u ith a parriculx spectrurn. sen& information about thc light

t t ) thc Imrn through thc ncrvous sy t cm. thcn the brain p rcusscs thc informafion. and tjnally the colour is

pc rcc~ \cd . Coltiur 15 r)Ïtzn a ~ s ~ ~ c i a r e d ivith [hc rrnace and the nrime o f an objcct chat typically hrrs chat

so!our. I Icncr the colour namrs oranse and rrispberry. for esrimple- The way people express colours is not

prasticil \vlic.n the colours nettd to bc speciticd in a manuhcruring process. in scientific studies and in

vartous businesses. Mriny researchers have h u n d thrit the values obtained through instrumental

mclisurcmcnts arc usetut ~vhcn thcy cxchange informaticin on colour.

Colorirnetry is regcirded a s ri subject in psychophysicb that strctches ricross psychology. physics.

physiolog~~. and chcmisrr~. . Colorimetry was rizcepted a s a quantitative rinalytical method in the 1930s after

the rcdclin~tion and rigrrcrncnt on the basic calorimetric terms. (A2oston.G.A. 19S7. p.47).

-1'hr.r~ :irc niriny diffcrent rypes o f instruments thlit merisure colour o r lighc receivrd from samples. A m m g

~lio'ir: t y c s of tnsrruments. ri glrissmerrr measures specular retlcction thrit ripperirs shiny to the h u m m eys.

but i r docs not rnzasurc colr~urs i BI'K-Gardner Catalogue. 2000. p. i 3). Instruments crilied densitometers.

tintomcrcrs. colour cornputers, specirorneters. spsctruphotomsters and colorimerers a11 measure colour wiih

various rncchanism~. These instruments are termed opricul irisrr~cttictits in gcneral (Skoog,D.A., et al. 1998.

p. 1 S 1). Instruments t h a dctïne the colour of 3 sampie. such as a specuophotomcter and a colorimeter are

alsu callcd cololri- I I ~ S I I - I O J ~ C ~ ~ ~ J - (5inyder.M.R. 1999). For opticsl instruments and colour instruments. the

nomenclmm is "not sgrecd upon and used by al1 scieniists" t Sko0g.D-A.. et ai. 1998. p. 1 S 1 ). What is

more, diftcrent tields o f study employ diffcrent types o f instruments under the sarne nrime. For exrimple.

spc~.trophotomctcrs rire tound elsewhere on university campuses prirnarily for absorption mrasursmznts on

transprirznt (oficn liquid sampies while another type of spectrophotomeier is frequenrly used in a n and

conservation and colour industry Ii)r measuring the rctlectrincc ol 'opaquc surt'nccs.

The n:irtieh o i the instrumenrb for ccdour mc:i.surement (coltwr instruments) are dctlned in rt tcxtbook o f

instruriiental analysis. and :ire quoteci herc (Sktwg.D.A.. et :il- 190S. pp. 1 S 1- 1s t 1.

"\i'e use the tcrm colorir~icrcr to d r s i g a t e an instrument for absorption mcasurcrnents in \vhich thc liunirin eye serves a s the dctector using o n e or nicxe color-comparison standards. A plznîorrterer- consists o f a source. ri tiltrr. and a photoslectric transducrr as well as ci signal processor and r a d o u t . It shouId be noted thrit sonic' jiienti'its and instrument manufxturr rs reftx to phcitometers as cnlorimeters o r photoelrctric colorirnerc.rs. Filter ohotornctzrs arc commcrcially availabk for absorption mecisurernenrs in the ~Irrriviolrt. visible. and in f r a rd regions. ris \ \ d l as emission and tluorescrnct. in the tlrst two ~vavrlength regions. Phocorncr~rs designcd fur fluorescence mc;tsuremcnts are also salledflrrorornrrersSSS (Skoog.D.A.. et cil.

199s. pp.1SI-182). ".A sjwc.rroutrrer is an instrument chat provides informriricm about the intsnsity of radiation as a

iunction of \\.ri\-r'lzngth or frequrncy. T h e dispcrsing modules in some spcctrometers rire multichannsl so ~ h a t t ~ u or n l ~ r e frsquencies san bç viewcd simultaneously. Such instruments are somstimes crilled pnlvc-111-o~rrtrtnrs. A spccrropl~orotnc.rer is a spectrometer equippsd with one o r more exit slits and photwlectric trrinsducers that permit the dctrrmincition of the ratio of the po\r.er of two becims as 3 function of \vcivc'len~th as in absorption spwtroscopy. A spcctrophotc~rneter for fluorescrncr anrilysis is sorncstimes crilled a .s;>c~c-rrofl~toro~t~erc~r." (Skoog.D.i\.. et al. 199s. p.lS2).

.MI insrrumcnts quured cibote "emplc>. tllterb cir monochromritors tu isolats ci portion o f the spectrurn for

merisurement" (Skoog.D.A.. et al. 199s. p. ISZ).

hSTh1 -' mentions [\vu types of colorinirter in ASTM Standards E 1347-90 (.ASTM El347-90. 1992).

These arc' tristimulus (filter) colorimeters. alsu knoum as color-difference metcrs. and spectrocolorimeters.

.A rristirnulus (Filter) colorimetrr producrs coluur coordinates and colour d i fkrences ris output. but it has

onty lirnircd absolute accurary and is not capable o f detectins metamc.rism. Nonethrlrss. a tristimulus

(tilter) cvforirnetcr is grncrally suirable for a11 objsct-colour specimens. (ASTM E 1317-90. 1992). .A

spectroçolorirneter 1s "a spsctrophotorneter that is normally capable of producing as output colorimetric

data. but not the undrrlying spectral data from which color coordinates rire calculrited" (AST-M E1347-90.

1992 ). \vhereas a spccrrophotomctsr produces specrrrtl data ris ourput. (ASTM E 1 164-9 1. 1993).

'' Thc i\mc.ricr\n Society for l'csting and Marcrials (ASTM E 13.17-90. 1992)-

:l srandard practicc t;)r spectrophotornrtry irn lluorescent rnritsririls is recornrncndcd by ASTM (ASTM

-- E 1 164-9 1 . 1993): "Fluor~.scent spccirnclns should bc: mcasured for wavr l en~ ths b e g i n n i n ~ rit 300 nm " if '

thcir ~ h ; ~ r ~ c r c r t s t i c s \vhcn illuminatcd by daylight rire desirclci" ( ASTM E 1 ICA-9 1. 1993 j.

The iolIo\\ing 1s an rx;implt. for ;in ripplicarion o f colour merisurement in heriragc cvns~'rvrition (,Cfoc/cr~l

P t r r r ~ r Cotrrr~i~ys S3. 1903. pp.-35-37,. The Xational Park Scr\.ice (U. S. A.) used spcctrophotomstry in

conjuncticlri uith the XIun~cl l Colour Xotaiir~n for i~s I-iistoric Structures Restorrition Program ris a means

0 1 ' matching the original priint col t iur~ and describing them in a n.ritten h r m . The National Park Ssrvice

cinticipcitcxi rlicit the paint cotour record would enable the priinrers to "have a standard a-riinst which ro

miwh thrir paints while caring for this important building in perpstuity" (Modem Plrirrr & Coc~ri~i.gs S3.

1993. pp.75-37). .-Uso. rccognizing and maichin2 of priint solours helped them to identify the original

scctions of tvwd work still retaininz the original paints. This paint colour resrarch o n old buildinzs \sras

conducted rit the Independence National Historic Park in do~vntown Philadelphia. The removrible colour

chips of the MunscII Book o f Color (hlacbrth) \ifrre comparsd to the priint samples under ri microscope

i 7x ) ,and to rhe paints in hard-to-rerich arcas such as high cornice mc~uldings. If necessa-. the colours of

the chips thar rnritchcd the priint colours could bs merisured th sp~.ctrophotornetsrs. thus assigning both

the Munsdl colour notacion (ri number or a combination of numbsrs and lettzrs) and spectral data to each

>ample. The i.isual paint colour identification o i the National Park Service \vas further vcrified by thsir

c.r)nsulrrints including Frank S. Welsh. Welsh tirst comprired paint samples from the histcrric site. thrit w ~ r e

r n c ) s r l ~ too srnall for direct spectrophotornerry. ro paint cards obtained from various rnanufacturers to tind

the pai nt cards that closei y match rhe spçcimens' colours. Then the CIE coIorimetric data of the paint cards

obtrtined rhrough spectrophotornetry. and finally. the CIE colorimetric data were c o n v e n d to the

hlunsell Crllour Notation for crich painr sampk from the historic site. Welsh mrrisured the colours on some

parts of the hisroric building directly with spectrophotomsttrs under ri light that illuminate the srimples

-. ' In the sccricm ".4ccelerarcd Fading" in t h i ~ thesis. spectrophutometric measurcrnents on daylight

Iluorcsccnt pigments u w e performcd between 330 nm and 720 nm. T h e instrument used t ,r the cxperirncnt. the Spectrogard II Color Systcrn. \vas not capable of measuring below 380 nrn.

Coloirr mc:isursmc.n; is a tzry ct 'kcti\.r m c r h d ro record w l ~ u - in a h r m that is objective and universal, a s

rhc :lmcricrin Natir)nal Park Scr\.icc dixo\ .cred (.+!utfc*rrt Ptrfur cY: Coczfirt,y r 83. 1993. pp.35-37). Whcn

non-dcstru~'ti\x colour wnsing is nccesstiry 2nd tvhcn the nesriri\.e ctf;-ct on the object causc'd by the colour

rnc:tsurernsnt ~cchnrquc is ri ccincern. besidch the ridvanced ';pt.irrclphotmncters that \vert uscd for the

Xational Park's project. eithcr ri chargr-coupled d w i c r (CCD) o r f ibre optics may bc amon2 choices for the

researcher-

Applicritions c)iCCD colour Jctcctors arc reportcd by C'riilxi. e t al. in rhcir study on non-destructive cciluur

rncasurcmcnr on paintcd ivorks r>f art. and b> Lrng. et al. in rheir srudy ,in colour rncasurcrnent of food

( Lin2.P.P.. et al. 1996. p.46) (\'allriri.XI.. et rit. 1994). I n the muscium and consrrvation ~vorld. \fAS.;\RI

prt)jects t.rnp1oyt.d CCD tiir thcir image scanners (V .ASMI j ianners) to acquirr: high rcisotution. t\vo-

dimcnsionril colour images for c a t r i l o ~ u r n ~ anci rcwrds (Burme~tcr.A.. c f al. 1992) (VASARI). CCD is also

used ris sensor o i infrared crimcrris to shoot IR retlrctograms (Hodkinson.1. 1999). h CCD is an arrriy of

lighr sensiti\,c diodes kvith a Ii$it rransrnittance tilrer in fronr of sach diode (Burmestrr.A.. sr al. 1992)

iSaundcrs.D. 1993). ln the crise o f the VAS.mI scanncr in London. rhe lighr irom a samplr \\.as receivcd

b'. a 5c1 o f diodes tvith ri rrd. a green and ri hluc filrer ior each. then the light energy wris converted to

t ' l~'ctric hignals. io the CIE '' X. Y. Z vti lur~. and svenrually tu the C I E Lzazb* values (Saunders.D. 1993).

Thc colorirnetric advantages o f C C D camcras (CCD coIour drrrctors) above spectrophotometers rire CCD's

si~niticrinrly higher spatial resolution,'* 1ergc.r number of simultrineous sampling points. and rhr consequent

ct'ticicnc>* in sxnpling. A s anothcr advrintagc CCD's high spatial resolucion allo\vs the operator to collcct

- 4 The Commissinn Internritionalr d 'Ec la i r a~ r (CIE). - 7 Spatial rcsulution here is ri v n o n y n ofrssolution ris grade of lensrs in photography and microscopy. Rc3c)lution is delincd as "rhc abiliry to disrin;uish - rrsol\.e - m u I l sparial dstriil" (Levko\vitz.H. 1997). Equ~prncnt \\.;th high s p a r d rrsc)lution is rspccted to b r geometriçrilly sensitive and is able to producr a 4;li.irp. derailcd iniagc as output. Kcsolution crin m u n the b i g a l srnsirivity o f an insirument.

1:ihrc c)pticb ret1ect;incr: qxctroscopy i FORS) \\.ris conducted by Bacci. st al. for non-destructive

rnvcsiigaticm ot' painring'>. Thrcr objcctii.es \vert' pursued usin2 tibrr optics: pigment identification. and

docuriicn~;ition c)t'colour chmgcs induccd in paintings b? the environmcnt (lisht. pollurants and sc> on).

l'tiltir insrrumcnt consi.stt.d d a spltctrum anal>scr tGuided i i -ave Mod. 260) and ri \\,and t y p e probe. The

opric;iI tibres for illuminating thc srirnplc and the optical tibres for recrivins the lieht from the sarnplr were

rnctdc in une bundlt: t c i t ixm the pri~be. The retlectancr in the visible and intrarrd region (400-2200 nm) was

mc.asurcd. Bacci. et al- concluded. "whrn a complete rttference data base is available. this technique can

hclp in rclirihle piynent identitication." tBacci..\l.. et al. 1992. p.275).

Colour merisurement is a "teshniqut: uf quantitrttive analysis." (iCIil1ikin.B.L. I9S3. p.1339-1350). There are

clc.rncnts 1 0 kcep in rnind 3s rt rulr of thumb thrit applies to r i I I sorts of measurement for accurate and

w x c s s f u l rinrilys~s. as Mi llikin suggcsta. "rrprcsentative srimplr. preprtration rnethod which is both

rcpcatrible anci repnducible. standrird material t;)r comparative measurement. and acceptability lirnits"

( 5Iillikin.B.L. 19S3. p. 1 X O J. ;is \ tel l as a detecting dzvicr u i th known rcsponse charricteristics

( f L>lfinrinn.K. 1976 j.

'-11 1s o tic1 [ t u t r i I I people do nor perccive colors and color differences the same. Some of this is due to

physiologicril differrnces in the eye. and somr is psychologicril. It is surprising how many people routinely

pcrforming color grriding have Less than psrfeït color vision" (Huebnr3r.F.E.. et al. 1992. p.203). Still.

Xlillikin statcs. "the combination ot 'thr hurnrin q e and brain cire [ is] an excellent nuIl drtector; no

instrument does as iveII detcrmining whether tu'o samples are cxactly alikt.. Subjectivity is introduced when

[tic srirnplcs differ slightiy frorn caçh other. Color instrumentrition has dont: an excellent job of objectively

3rd quriniitritivcly describing color dit?'crcnces" (Millikin,B.L. 19S3. p. 1340). Ctowever. "since the eye is

tiighly hcnsirivc. IO srnall colt~ur d i f f renccs. ver! stringcnt rsquirernents have to be impused on the

:iccuraq oic010ur m e a ~ r i n g cquiprncnt" as 1-Ioifrnann argus3 (1-1oft'rnann.K. 1976. p. 14s).

Lf'hen the rchults o l ' c o l ~ u r rncasurcments are ic)mparcd and those mcasurerntlnts havc been perfbrmrd \s-ith

dit'tbrcnt instruments. particultir a r c rnubt bc tlikcn because rncrisurcrnrnts trith difkrcnt instruments o f t rn

ini < i l \.c. di ikrent parrirnctcr~. in'-luding the sen.slrl~.it' and r r s p m s r characreristics of individual

instruments. IloîYmrinn uarns. "sny indi\.idual errors. \vhich arc t o l e r a k ! ~ on their own. are additive in such

instances and, thrrcfore. may excesd the tolerrtnce threshold. The basic causes o f the errors lie in the

\srivelcngth scalc and in the lincariry of the photcimeter re!lectrince o r urinsrnittance scale." (Hoffmrinn.K.

1976. p . l l S ) .

1 luebner. ct al. point out that quriliry control is nscessriry to have and use standard reterttncçs for colour

rntxsurcment. The' found somc cornmon probiems that Iriboratories tend to have with standard rsferences:

dixcilouration. unknwvn purchase date. and t'riilure in complying \vith ASTM standards. The stsbility of the

i ~ i l o u r of'strind;trd rekrcnces m a i bc dit'fcrcnt cfcpending on the [ypc of the srandard. for esrimplrl,

rrlinspcirent o r opaque, and plastic o r ccramic: hotvevçr. the importance of qurility control of standards

crinno[ bc overcmphasised. (Hurbner.F.E.. et al. 1992).

.As parrl;blr colour instrumenrs have bscomc availribte. coIour mçasuremenr hris becomr more msriningful

in activitics to conserve art and heritrige. Ar the Canadian Conservation Institute, Ottawa, Crinrida, portable

w1c)ur instrurnznrs (~Minoltri CR 200. hlinoltri CR 23 1. Minolta CR 300. and Minolta CM 2022) hsvc bsen

usrd for merisuring the colours of rirchaeological textiles. oïl painrinss. and s o on. Thc Institute also bas a

t~cnchtop type colour instrument (Spcctrogard II Color Systrmj. The benchtop cypc colour instrument is

supcrior to the ponrible colour instrument in the riccurricy and the repeatability of mcasurernsnrs. and

rhcref'orc. i t is uscful ti)r colour mcasurrrncnt of stabIe srimples and srimples t'rom surrogrttt. rnodcls:

h~)\t.evcr. fragile s;~mples. Iargc objccrs and thrce-dimensionri ubjccts cannot be rneasured \vith the

ticnihtop type instrument. This is because the mnpie must be held in the srirnplc holder during

rnsa~urcrnent. The poriable c d o u r instrumenr nc)r only trikes ri vriricty of types o f stimples but also riccepts

in-.situ (ibn-site) mcasurcrnent. Thi:, means thar the srimpie o r the objcct does not have t o traveI from thc site

t o t1ic an.iI>ticril hc i l i t y r iAing i rh saÏcty. and thrit the srimplr o r the object has less chances o f bcmg

d~irnagcd b!. handling. by rin accidenr. or by cin i.nvironmcnra1 change. In many crises. a portable colour

insrrument is capable of conducring non-desrructivc colour merisurement>.

Porrribls colour instruments arc' Icss e s p c n s i ~ e . and are cris' ro use. but di) not aI\v+s have h i ~ h riccuracy.

dtliough somt: o t ' t hem art: gwd snough to be used for quriliiy control in plants. Benchtop l a b o r a t o r units

cosr more rhrin porrabit: onrs , but art. casier w use for srimples wirh irrssular surfaces. such a s groups o f

pc1lc.r~. 2nd art. h i g h k accurate. Xcross the io lour instrument indusrry. portable colour instrumenrs range in

prlcr l'rom S6OOO t o $9000 (US). and benchtop uni& crin cost SS000 to S20.000 ( U S ) ris o f 1999.

( Snydcr.3I.R. 1999. p.45).

Blue-wool Standards

Bluc-\r.cwl is a standard indicritor of the total light dosrigc th21 a surface receives durinr a certain period of

rime. B y referring to 3 SC[ ofst .~ndard blue-\vools ris their colours t'ride to vrirying extents. it may become

r:;~hier for w m c people tu understand the light dosage on samptes that is mr'risured by an integrriting

Iightmcter and then cspressed in mathemriticril t i p re s . Generally. the \vord fade refers to "becoming lizhter

in cu1c)ur." ot'tcn ri5 a resulr c>fchcniicri! chanse in the c d ~ m n t . Therc are more types of blue-wu11 standard

23 ;Ire mr.ntiimr'd lritr'r.

Bluc-n.ool standards crin bc uscd in difkrent ii.ays. Thc lishtfristness of a specimen is detrrrnined by the

bluc-u.oc)l atrindrird that 13 ris lightfast ( o r fugitii.~') as the spccimcn. Aiso. the total effec-cts from radiation on

s qxx5mt.n crin be measurcd by the colour change of thc blue-\\.ool standards. The exposure results shown

by ri set of'blue-\vod standards crin bc rcçonciled with the numerical figures (e. g. miIliwatt hours per

square centimeter or footcandle hours) obtaincd throueh instrumental merisurement run sirnultancously.

during cirhcr conrinuous o r discontinuous illurninriti~in~ (Fe1ler.R.L. et al. 19S0. p.43).

The cvalurition of the lishtfasrncss of a specirnen is made when the specimen fades "jus[ perceptibly"

i Fc.1lcr.R.L. et al. 19S0. p.45) (Gi)ldmmn.h,l. b. The colours of somc of the blue-wool standards mciy becomc

- - --

" ISO Krcornrncndation R I 0 5 1. Parr 1 1 (Fel1er.R.L. et al. MC 197s). - - Brirish St;i~iJrird.

The cstent of fading 01' the bliie-\vciol standards; crin be espre..ssr.J in rclatiun to the bluc-wool standards thar

hri\c n<,t bccii esposcd ru Iigtit. A s ;t rekrericc for this mcthld. the contrristb bct\vc:en ~ r c - s \\.;th ciiïtt'rcnt

hh~idc:, tin ri .standard grey sc;ilc rire utilized. The rcçonirnendrd grcy scrilcs arc the Gcometric Grey Scale

ES2663 rinci the equivlilent g r q scale used by the Arnerican .Association of Textile Chemists and Coiorists

(AXTCC 1. i Fel1sr.R.L. e t al. 19SO. p.4 1) .

-1'\\t\ o r thrcc cnpcricnccd obscrver~ must participare in the juJgernenr on the fading of a c010ur in the blue-

\\ooI s i ; t l ~ . Thc cxrcnt ol't'riding 15 ratcd one t~ cight. In halt'stsps of' the blue-~vool standards. and

;1ver;tged. \Vhen the conditions of thc exposurr arc: the same. the ratings made by rxprriencsd obssmers

u~urilly q r c e \vithin one blue-\ \wl step. Ifrhc rcitings vary more than one blue-\sud step. the rssearcher

rnubt sonsider the dcviritic)n in the exposurc environment. I;)r rsample. temperature. hurnidity or spectral

charrister of' the illumination. (Fcl1cr.R.L. et al. 19SO. p.JS) tGoldmann.hI.).

A'; Ions ris the biur-wooi srandards rire evaiuatcd visudly. crrors and disagrccrncnts arc inzvitablc in order

to miticrite the inllucnce o f subjr.ctiv<: judgernent. the Mrllun Institute "' rccomrnends classifving colorants

in thrw drgrees of photochernical stabiltty. (Fr1lsr.R.L. et al. 19SO. p.4S).

Clriss A: excellent o r stable: rqual to or more stable than the blue-\vool standard number 6

Class B: intermediate: equivrilent of bluc-uool standard numbcr 3.5 to 5.5

Clribs C: tugitivc: cqual to or Ichs stable than the blue-tvoal standard numbcr 3

Fe1lt.r sugg~_csts. "The u x oi just thrrc gencral classes should rcducc the occasion for argument and

disigrecment about which marcrials arc fusitive. Lvhich highiy stable. . . .." (k1Ic:r.R.L. et ai. 1980. p-48).

7 . The phenc~mcnon of darkenins also occurs 10 d a y l i ~ h t fluorescent pigments. 71)

intcrp)latr: to tind rhc point tvhsn thc sptmmen srancd to hdz. S J Thc Center on the %lritcririls of the Anist and Conservator. Crirnesie-Mellon Institute of Research. P i t t d x q h . PA. US.-\ (Fcl1er.R.L.. ct al. 1979).

Soncthclch~. "Thzrc is no harni in rcporling the bluc-irool cquivrilcncy of ri colorant-' if thc evaluation ih

c r i r r id OUI in ri propcr manncr ( f~cI1cr.R.L. sr al. 1980. p.4S j .

I'hc i d i n 2 01' b luc-nr~ol srand;irds c m be monirtired by an in~trurncntal niethod. if the objectivity r)f rhc

judgcrncnt km fading i s a conccrn. Fctler proposes tr) use the lurninous retlectrince (the CIE lurninrincc: value

1'1 riic:,~urcci ~vith ,n inwunient that is able to nicrisure the rt.tlcctrince of a small rireri." .AS Fcllcr

rc.cl)riirricnd~, the ctiringc III 1- \aIuc ( A l ' ) 31 tlic iva\clcngtlis o f the mastmurn abscirption of the individu31

bluc-\\.ci01 standards should be rnonirorsd. and the A l ' ar 620 nm '' crin b r used. altrrnativeiy. (Fel1sr.R.L.

et al. 1979).

ISO R 105 blue-\wol standards werc "c)rizinally developsd su thst thcir dégrse of fading could bc: ratsd b', a

siniplc \.isuril mcthod" (Fd1er.R.L. cl Y I . 1979. p-301. Bttliard furthrr drscribes thé nrsd of blur-ivool

standards rit the tirnt of develr)pment. "The purpose of 'Blue Wool Standards' - either British or American

s: - is r t i provide ri rnerins of compririson bet\\.scn the eftect of light on one series of samplss and that of

:incdicr. The BU'S '' \vcre in~ti tuted ;lt a timr \vhen the spectral distribution. intsnsity, blrick body

tcmpcrriturt. of a light source cc)uld nor be rnonitored. The B\VS rnable textile coloris& ro predict the

rcI;1~1\c cfiect o f lisht upon ri dycstuffon ri given subsrrritc rit a prirticulrir depth of shadr" (Bril1ard.M.W.

1'9S5).

The Mcllon Insritute tound that the blue-wool standards are one o f the few available rcference standards for

photochernical damage on various materizils. for example. ceiluloss. varnishes and organic stabilizers

S i F d l r r used Kollmorgrin Small-Area-\'irw (SAV) Color-Eye. s 2 The colour of light at 630 nm is reddish orringe. The r a s o n to choose this wavelength is not clcar. honcver. Fèllsr draws an example from a preceding study done by Fr iek in a similrir way. In another esample. the blue cellophane chips provided by PPG Industries Inc. are subjected to spectrophotomztry a t 5 10 nm (green). Whcn blue chips absorbs ultraviolet lisht. the colour of the chip is changrd irreversibly iind the oprical densiry of the chip. mcasured ir'ith spectrophotomster. is used as an indiçator of the chipas ultraviolet light exposurc (Dieh1.D. 2000). >:

The dyes uscd for the American blue-wooi standards arc spccitied by the AATCC and rire different from the dyes i o r the ISO stcindard bluc-wools fFel1t.r.R.L. Fort Worth 197s. p.73). 5 4 B lue ii:ot)l Strind:irds.

i i:cIIcr.K.L. et al. LOSO. p.51). This is rnainb because :in instrument such as a lightrnetcr merisures only the

anit)unt oicncrg! t h ~ t rcccivc~i on the spccifi~- sur1;Icc. but 11 does not measurt: the extent of the chernical

or ph~sic-;il changss that ti)llo\v rhs irraciiation. Feller sees ancirher problern in inhtrurncntal rrnrilysis: the

rcsulrs 01' nieasurernents dit 'kr ;inlong the types of instrument and arncinz the individual instruments of the

same t>l~e. duc to "the responsc characteristics the instrument. its \\favzlength sensitivity o r selectivity.

i l3 ca1ihr;ition. ctc'." ( Fc1Ier.R.L. ct al. I9SO. p.50). \vhereas the methods \vith blue-trool references arc

5 t a n d x J i s d .

Blue-\twd standards are not pcrtilct. as Feflcr acknowledpes. The blue-wool standrirds "do not fiide idzrilly

such thai e x h one fades precisely half as fast a s ihe prsceding number. The di fkrent dyes ernployed " also

\,dry somen.hrrt in thcir sensiti\firy to uftravic)lct radiation. tzmpsraturs. and hurnidity. I t malr be that in the

tuturc. ;t singlc r e t r cnce standard u5fl bc: developed . ..." (Fel1er.R.L. et al. 19SO. p.42)- Blue-wool

standards. hr,\vevt.r. have some irnporrant ad\.antages: the blue-~vooi standards are relritively inexpensive

2nd arc ~ntcrnationally rccogniscd. (Fc1ler.K.L. et al. 19SO. pp.42-13).

.-13 kir an application of the blue-~vool standards to detect cc~lour detcrioration caused by chemicds in the

cnvironrncnr. Ballard states. 'These standards are not used if the object of the study is. for example. fume

t'ridinz by ozone. 5inc.e their reactivity is nor consistent o r conductive for chat particular srudy. Instsad. other

>tandards uith a specified dye rit a specified concentrsition on ri specifkd substratc arc uscd: these standards

rire susceptible to ozone fading at a known rate" (BalIard.M.\ir. 1985).

In conciubion. the use of blue-wool standards is not fret: frorn rrrors and deviations that occur in the

nianu fricturing process. in hrindling ( (includes trrinsportation. storrige and application) and in j udgement of

fading. Fur similar reasons. instrumental measurernent aiso requires precautions, cheretore. the choice

'' The rirticle (Fc1It.r.R.L. c; al. 19SO) does no; specify whether the "difirent dyçs" means ri dit'krent dye r i a d ior tach bluc-\vu01 standard nurnbcr in the srime set or the differcnt dyes used by diifersnt rn:inutrictiircrs 01' bluc-wool. \1 , l'tic bluc-\rciol standards.

4. Experiments

Accelerated Fading

4. 1. 1. Introduction

Daylight tluorescent pigmenrs have been on the market for many decades. and a variety of everyday items

have been coloured with daylight fluorescent pigments. In the tield of modern an. daylight fluorescent

pigrncnts have played a significant role becauss of their sensarional optical propenies and because of their

poufer to attrrict the vie\vers' attention. Now. somz anistic products of daylight fluoresce are raising

conservation concerns because of their unstable colours. .As everyday items in fluorescent colours becoms

old. they mriy bccorne objects ot'cultura1 o r rthnographic heritage. and they will aIso need conservation

treatrnrnts.

In mriny cases. conservation treritrnents includs inpaintins, a technique to visually compensate surface

losses on objects. Thc technique includes the following steps. A loss on the surface of an objsct is filied

nith an appropriate material, a thin layer of synthetic rcsin is ripplied over the f i l1 as a protecrivt: coatin_o.

and then thc tÏll is inpainted so thrit i t s coIour matches the surroundins area. There are two common

approaches to inpainting The first one is usin2 a colour that is similar to the surrounding but not exactly

the same. This rnethod is used for the treatment of objects that have a historical o r an academic importance.

The treated parts must be distinguished easily from the original parts so that the treated pans do not

interfere when scholars and conscrvators assess the ori-inal pans. The second method is to match the

inpainting exactly to the surrounding orizinal so that the ueated parts are not easily distinguished, thus

recovering the object's aesthetic value.

Driylight fluorescent pigments lose their original appearancc in ri short pcriod o f timc. compared to anist

p d c non-tluorcscent pigments. It is very diftlcult to rnritch rlic inpaint to the dcterir)rritsd driylighi

tluorc.sccnt colour of thc object whcn a conservalor wishes to obtriin an exact match. because both the

ret'lected colour and the fluorescence must be matched. Since the use of driylisht tluorescrnt matsririls by

artists is now cornrnon, it is only a matter of time before a n conservators are challengrd by these daylight

fluorescent mciterials.

In art conservation. scientific information on fluorescent pigments is not abundant. Although fluorescent

substances are studied and used in many other fields. the focus o f study is specific to a c h field of study,

therefore. the information required by art conservators is rarely found in the literrtture from other fields.

Drtylight tluorsscent pigments need t o be studied as artists' priints and a s decorative painu to meer the

requirernents of art conservation.

4. 1. 2. Objective of This Espcrimcnt

The main purpose of this experiment is to collect brisic data on daylight fluorescent pigments in terms of

colour deterioration. It is very important to have basic data as tirm evidence to support a theory that

explains a phenornenon. This experirnent will rcvcril how the optical propenies o f daylight fluorescent

pigments change as the pigments are darnagcd by light. The results gained from this experirnent will help in

understanding the theones on the optical propenies of daylight fluorescent pigments in textbooks.

Another purpose of this experirnent is to present information in a form that is convenient for a n

conservators. The data will be analysed in the way that conforms to the interest o f a n conservaiors.

rnuscum specialists and others in the art world. The usefuiness and limitation o f instrumental colour

merisurement for a n conservation will also becorne clearer.

4. 1.3. Espcrimcntal Set Up

In this rxprriment, paint samples were exposed to intense lishr. and the process by \vhich the samplrs lose

thcir colours \vas obsrrved. Thcre were thrce sets o f samplrs in this experirnent. The t h set of samples

wcre subjrctcd r o the Siinligitt Erposrcre experiment. a simple exposurc to sunlight indoors. This simulares

a case in which a painting is hung o n a vcry sunny wall in a room. The second set o f samples was subjected

to the Alterrintive Serrittgs Ekposrrre experirnent, an exposure to fluorescent lamp iilurnination under a

cornbination of different UV filters and humidities. The third set o f samples for the Swp-by-Srep Fading

experiment ivere also exposed to the illumination for the Alternative Settings exposure expriment. to make

the sarnples fade to different degrees s o that they crin be used a s materials to study inpainting for faded

driyfight tluoresccnt pigments. Lists of instruments and sarnples are attached (Tables 8-10).

Sarnple Preparation

Sarnples were paints applied to cards and dried. Five colours from threr different brands o f daylight

tluorescent priints \ v u e chosrn: WaIlack's student grade acrylic paint Fluorescent Yellow (coded as

'-WFY" in this study), Wallack's studcnt grade acrylic paint Fluorescent Orange (WFO), Wallack's student

grade acrylic paint Fluorescent Magenta (WFM), Liquitex Concentrated Artist Color acrylic Fluorescent

Orange (LFO), Utilac spray paint for interiorfexterior Fluorescent Red (UFR). A non-fluorescent paint was

chosen as ri reference: Wallack's Lemon Yellow (WLY).

T h e card that supported the paint samples, o r the substrate. was ASTM Standard Form 3B for paint opacity

test. This form is designcd for opacity testing on thin paint films. therefore it has a black border on the

\vhitc surfi~ce but only the white part was used for srirnpling (Figure 42)-

Thin p i n t samplcs (codrd as "r" after each paint type code) were preparcd by a rnrthod called cfrawdowtt.

Esch type ofacryliç paint wris directly sprcrid on an ASTh.1 Form 3B with a drawdoun bar. which is also

crilled ri film ripplicator. The thickness o f thcse thin sample paint tilms was 1 0 0 pn ( 4 mils. for WLY.

WFJ'. \VFO, WFM, LFO) when they were wet. Thick priint sclmples (coded as "p") ivere prepared by tape

mouldinz (for WFO) or spraying (for UFR). For tape mouIdin2. a trench was c r a t r d between two low piles

of rnrisking tape on an ASTM Form 38. The acrylic paint \vas spread in the trench, to an even thickness

using ri glsss microscope slide. and the paint was dried. A feu. Iayers of masking tape were added to both

pites and this proccss was reperited until the paint film becarne thick enough to obscure the black border

printed on the substrate. The Utilac paint was sprayed directly on an ASTM Form 3B in a &in layer and

then dried. This process was also repeated until the paint tilrn became thick enough to obscure the black

border of the substrrtte. Each sarnple was trimmed to 3cm x 3 cm squares with substrate and rnounted on a

5 cm x 5cm square of a thick. hard and white card. Double sided tape was used to adhere the slimpls onto

the crird.

Some of the rnounted samples were kept in the drirk as unexposed references. Al1 the unexposed references

ivtre stored in paper boxes that were Iined with black paper. This box was placed with a hygrotherrnograph

in a Iriborrttory at the Cansdian Conservation Institute, so that the unexposed references and the

hygrotherrnograph did not reccive direct sunlifht.

Sunlight Esposure

Samples for the Sunlight Exposure experimrnt were the thin Wrillack's Lemon Yellow paint (WLYr). the

thin Wallack's Fluorescent Yellow paint (WFYr). the thin Wallack's Fluorescent Orange paint (WFOr). the

thin Wallack's Fiuorescent Magenta paint (WFMr). the thin Liquitex Fluorescent Orange paint (LFOr) and

thc rhick Liquitcx Fluorescent Orange paint (LFOp). Five thin sampies ("r" s ) were prepared with each of

WLY. WFY. \IFO. WFM and LFO. For each type of paint. three samples were exposed to sunlight and

two srimples were kcpt in the dark but in thc same room as the unexposed references were. Threri thick

samplcs ("p" s) wwe prepared with LFO: t ~ o of thern were esposrd to sunlight and one o f thsm was kept

wirh the other uncxposed references.

A set of ISO Blue-wool References (Golden BIue Wool ASTM Standards) wris exposcd to sunlight d o n g

with the sarnples. The set consisted o f eight thin strips of fabrics dyed in different shades o f blue. and the

strips kverc: aligned side by side on a card support in the order of their light fastness. A set of the blur-wool

standards wris cut in half across the width o f the strips and mounted o n a slightly Iarger pieces of card. as

the paint srimples were. T h e resulting size o f sach stnp w s 9mm x 23mm. and the total area of eight strips

was 7Smm x 23rnm. The blue-wool standards were incorporated in this experirnent in order to facilitate a

visuai understanding on rhe iight dosage dur ins the experiment. T h e blue-wool standards are a set of fabrics

dyed in vrirying lightfastness so that the extent they fade indicatc the approxirnate arnount of light a surface

receives during a certain period of tirne. T h e lightfastness of materials and the illumir,~tIon dosage are often

referred to the corresponding blue-wool number by conservation and museurn professionals. Thc blue-wool

standards rire furthsr discussed in ri dedicrited section.

In total. seventeen samples and two sets o f the blue-wool standards were attached to the exposure panel

(Coroplast. 3 fluted plastic board) and then secured on a glass window. T h e samples and the blue-wool

standards were attached to the exposure panel with staples through their card mounts. The samples and the

blue-wool standards were always handled by their card rnounts and were never touched directly. Small

spricers were attached between the exposure panel and the window glass to keep the samples from touching

the window glass. The exposure panel was secured to the window zlass with masking tape. T h e blind wris

scrolled down behind the exposure panel, thus ieaving the samples between the window g l a s and the blind.

For the Sunlight Exposurc experiment, the samples mcntioned above were venically aligned about 5 mm

away from the intcrior o f the window glass on the south wall of a laborritory. The glass panels of this

window had no UV filter. The samples were exposed ro sunlight through two Iayers of windaw glass. ait

- 84 -

room temperature. Thc total dosage of sunlight was measurcd tvith an Elsec Integrating Lightmeter Type

790 (Littlcmore Sci. Eng. Co.). Thc ssnsor of this integrating lightrnetcr was modifird with an aluminium

cover to reduce its scnsitivity by a factor of 32. Occasionally the lishr intcnsity and the UV content o f

sunlight \vue measured at the position of the samplcs with ri lishtrneter. Cal-Light JOO/ModsI JOOF

(Optikun Corporation Ltd-) and a UV monitor. Elsec UV hlonitor Type 762 (Elsec). The room's

temperature and relaiivr hurnidity wcre continuously monitored with a hygrothcrrnogrliph, Isuzu Electronic

Thcrrno-hygrograph 3- 1 125 (Isuzu Seisakusho Co.. Ltd.).

Alternative Settings Exposure

Sarnplirs for the Alternative Settings Exposurs experirnent \vers the thick UtiIac Fluorescent Red paint

( UFRp). rhc thick Wallack's Fluorescent Orange paint (Ii'FOp) and the thin Wallack's Fluorescent Orange

paint (WFOr). Nine thick samples ("p" s ) were prepared from each of UFR and WFO. For four out of nine

samplcs of each paint type. the RI f (relative hurnidity) in the humidity chamber was kept at 50 %. and for

another four samples of each paint type, the RH wris O %. The Iasr srimple of each paint type ufris used as an

unexposed reference and was kept in the dark together with the unexposed references from the Sunlight

Exposurr experiment. In each hurnidity chamber. one sampls of each paint type was placed undsr a UV

filter. NRS-90 (a water-clear UV transmission filter. transrnittance less than 1 C / o below 335 nrn. 5 1 r/c at

4 10 nm and more than 80 % at 360-800 nm. Counaulds Performance Films Inc.). one sample of each paint

type was pIaced under another UV filter. Shinkolite (a water-clear UV transmission filter. transrnittance

less than 1 5% below 400 nrn, 4 9 8 at 415 nm and more than 90 56 above 135 nm. Mitsubishi), the third

sample of each paint type had no filter. and the Iast one of each paint type was under an aluminium cover to

exclude light. The UV tilters were raised above the samples. The aluminium plates were made into a box

shape ro cover the top and four sides of each sample and lined with black paper in order to eliminate any

light that might be reflected inside the aluminium cover and reach the paint surface. None of the filcers o r

ihe aluminium plates were in contact with the srirnples. In total. sixteen samples were mounted on square

cards as tn the Sunlisht Exposure experiment. The mounted samples were stapled onto largsr black p a p a

- S 5 -

sheers. \vhich were thin enough to transmit the mnbient humidity. This was necessary to block riny Ii-ht that

might have bccn rellccted o r r e t i x t e d by the silica gel substrrite and rcached the samples in crich humidity

charnbèr.

For the Step-by-Stcp Fading experiment. anothsr set of five thick samples ("p" s) and f ive thin samplss ("r"

s ) wrre made with the Wallrick's acrylic Fluorsscrnt Orange priint (WFO). These samples mounted on

square cards. ris well. A thick sample and a thin sample wrre usrd ris unexposed refercnces. and werr kept

in the drirk with the other unexposed references. Four thick samples and four thin samples werr stapled

onto a Coroplasr exposure panel and placed in the fluorescent light box beside the humidity chamben. The

samples were transfened from the exposure pane1 to the unexposed reference container as they achieved

èither of the prcdrtermined perik heights.

In the Alternative Settings Exposure eeperiment. the samples were placed horizontally in a fluorescent light

box. The fluorescent light box had 17 fluorescent light bulbs. The interior measured approximately 14s cm

x 127 cm x 30 c m and ueas paintsd white. The tluorescent light buIbs were VITA-LITWURO-TEST

40W. dnylisht type. and measured 120 c m long. Al1 17 fluorescent bulbs were kept on al1 the time except

for some short breaks. Two hurnidity chambers were glass boxes that were made of 4 mm thick soda glass

\vithout UV filter and merisured 50 c m x 50 cm x 10 c m at the interior. T h e junction between the lid and

the body of each g l a s box was sssriled with a mixture of silicon rubber and wax. T h e humidities in the two

glass boxes were maintained at O '70 and at 50%. respectively. by using conditioned silica gel. grade 30,3-S

rnesh. A hygrometer and a mercury themorneter were placed in each glass box t o monitor the humidity and

temperature of the intcrior without opening the lid. The room temperature was rnonitored on the exposure

board beside the glass boxes in the fluorescent Iight box. The room's relative humidity was not monitored.

The interior of the fluorescent light box was cooled by a large electric fan that ran continuously and

circularcd the room air through the light box.

Thc light intensiry and the U\' content o f the f uorescent Iight were monitored by occasional measurement

rirnund the humidity chambers.

In order to judge the colour change objectively. the colour of each srirnplr was analysed ivith ri colorirnetric

instrument crilled Spsctrogrird I I Color Systrm (BYK-Gardner). The main cornponcnt o f the Spectrogard II

was a scrinning spectrophotometer designed for surface colour measurement. This instrument illuminates

the sarnple with the type of light chosen by ihc operator. rcceives the lighr from the sample surface and then

separrite the light at each 10 nm. T h e wavelength of Iight corresponds to i ts colour. The light detected on an

i llurninrited sample surface is merisurrd as retlectrince by the Spectrogard II: however. in the case of

daylight fluorescent paint samples. the light detected on the illurninated sample surface consists of

retlection and tluorescence. (Spccrroprd II nrnmtal).

The Spectrotard II gives the spectral datri rit eaçh 10nm. the spectral plot. and the CIE L*aWb* data for etich

measurement. The data rire sent to a dedicated cornputer. compiled in its memory. and converted to an

ASCII file. Then the ASCII file can be exponed to another cornputer via a floppy disc and can be

mrinipulrited with softivare for general use.

The type of illumination used in the c o t o r i m r q was D6500 in the CIE standard, a daylight type. The Iight

source in the Spectrogard 11 was a quartz halogen lamp with a filter that ridjusts the illumination power

distribution to sirnulate the CIE ILL DuS. Another filter rernoved the infrrtred portion (above 720 nm) from

thc illumination in order to prevent the srirnple heat up. The operator can include and exclude the ultraviolet

portion (380-400 nm) from the iIlumination in the Spectrogard II by mrinipulating the third filtcr. Graph 1

shows the transmission specuum o f the UV fîlrer in the Spectrogard II. Graph 2 shows the reflectance of

the standard %phite ceramic tile with and without the UV portion in the illumination. The samples for this

scries of experiments are m m u r e d against this standard white ccramic tile. In this expcriment of

accelsratcd fading. the retlecrancc spectrri were taken undsr illumination with and without the ultrriviolet

portion. Thc observation \vas dune a i 10 dcgrees in the CIE standard. with specular cornponent (or spscular

rctlection) cxcluded. (Sprcrrognrd // r r c c r ~ r r ~ c i l ) .

The sarnplrs for the Sunlight Exposure experirnent were measured before the exposure started. rvery day

during the tirst three days. oncc a week for the following six weeks and then once every three or four

u.ceks. Thc sarnples for the Alternative Scrtings Exposure experirnent werc measured before the cxposure

strined. after rwo weeks exposure. three weeks exposure. seven weeks exposure. and then once every few

rnonths.

The sarnplcs for the Step-by-Step Fading experirnent were rnsasured every three o r four weeks. The peak

hcisht \vas monitored at e x h srimple's dominant peak on the reflectance curve obtained frorn colorirnetry.

The predetermined peak heights to terminate sample exposure were 90 52. 80 52.70 C7c and 60 5% of the

pcaks before exposurci for borh chick and thin sarnples,

Facility and Location

The expairnent was conducted at rhe Canadian Conservation Institute (CCI) in Ottawa. Ontario. Canada. In

the enrire building o f the Canadian Conservation Institute. the temperature and the relative hurnidity rire

controllcd to approximately 22 'C and 50 %.

Acronyms of sarnple names are repeated here for the convenience o f the readers:

WLY: Wallack's acrylic Lemon Yellow WFY: WalIrick's ricrylic Fluoresccnt Ycllow WFO: Wallack's acrylic Fluorescent Orange WFM: Wallack's acrylic Fluorescent Magenta LFO: Liquitex ricrylic Fluorescent Orange

UFK: Utilric spray for interiorfaterior Fluorescent Red r: thin paint Iayer p: thick paint Iayer

Graph 7 proves the consistency o f the data obtained with the Spectrogard II during this cxpsriment. After

bsing rxposcd to sunlight (the Sunlight Exposure experiment). the fluorescent paint srirnples Iost thrir

rrflectance values (Graphs 8-20). The deviation o f spectra arnong the samples with the sarne colour was

negligible. for cxample. the retlectance spcctra of the thin Wrillrick's Fluorescent Orringc samplss.

WFOrO 1. WFOrO? and WFOrO3. ciosely matched each other after the exposure. The sarnples kepr in the

dark riiso had matching refiectance spectra a m o n t samples with the sarne colour. and these samples did not

decrease in reflectance during the period o f the expeflment. The only exception was one of the thin

Liquitex FIuorescent Orange samples. LFOrO3. that faded to a greater extent than other sarnples o f ihe

same kind, LFOrûI and LFOr02 (Graphs 2 1-22).

The thick Wallack's Fluorsscrnt Orange samples for the Alternative Setrings Exposure experirnent

(sxposure to fluorescrnt Irirnps) declined in rctlectance while they w e n kept in the drirk without bein:

exposed to the controlled humidities (Graphs 23-24). The reflectance of the thick Utilac Fluorescent Red

samples (Graphs 25-26) decreased a t a lower rate than the Wallack's s a m p k s did (Grriphs 37-28). The thin

Wallaçk's Fluorescent Orange sarnples did not fade while they were kept in the dark (Graphs 29-30).

The fiuorescent samples exposed to sunlight gained reflectance values at some wavelçngths in the

beginning, and thcn the values declined. The thick fluorescent sarnples exposed to fluorescent Iarnp light

similarly gained reflectance values at some wavelengths. and kept on increasi ng during the expcriment. As

2 ger)..-rai tendency, reflectance kept on decreasing at wavelengths higher than the dominant peak. and

reflectance kept on increasing at wavelengths rnuch lower than the dominant peak. At the lower wavelength

close to the dominant pcak, reflectance first increased and then decreased. Sometirncs. a small scale

decrcrise of reflectance precedrd the increasc. Also as a general tendency. when reflectrinçe value declined.

there was a sharp drop in the early stages. thsn the drcrrasing rate slowcd down. (Graphs 3 1-45).

In the Sunlight Exposure expcriment. the samples' çolour change was obvious by visual observation. The

ISO Blue-woc,l References no. I - 4 and thc thin Wallack's Fluoresct.ni Yellow sarnplcs faded very quickly

in sunlight. and they bccarnc ~vhitish in a fe\v months (Table 13. Graph 33). Other tluorescent paints

exposed to sunlight also shoivsd a significrint decrease in their colour saturation in ri fçw months (Graphs

3 1-42).

As the priints lost their bright appçarance. slight hue shifts were detected with the Wallack's fluorescent

paints by visual observation: the Wallrick's Ruorescent Yellow srtmpies became iess greenish. the

Wallack's Fluorescent Orange sarnples becarnr more yellouish (or less reddish). and the Wallack's

Fluorescent Magenta samples becarnc less bluish. In the retlectancs spectra, however. the W'allack's

Fluorescent Magenta scirnples griined blue hue during rxposure whilr losing red hue. With al1 three

Wallack's fluorescent colours. the dominant peaks above 500 nm shifted toward shorter wavelengths

during the exposure to sunlight. and this result from spectrophotornetry irnplied that those colours becarne

more yellowish because of light damage. (Graphs 10, 12, 14). The Liquitex Fluorescent Orange samples

inspected visually less hue shift and less loss of colour saturation, compared to the Wallack's fluorescent

paint srirnples. The spectrophotometric analysis of the thin Liquitex Fluorescent Orange sarnples reveaIed

thrit the dominant perik hrtd slightly moved to\vard shorter \vavelr=ngths (Grriph 16j. The thick Liquitex

Fluorescent Orange sarnples did not have an apprcciable hue shift (Graph 19). The only non-tluorescent

sample. the thin Wallack's Lçmon Yellow paint. did nor show a visually appreciable coIour change during

the experirnent, although there was a slight decrease in reflectance at certain wavelengths (Graphs 6-9).

As was seen in the retlectance spectra of the tluorescent paint samples (Graphs 10-20). the troughs of the

reflectance curves were elevaied. and the pertks were diminished during the experiments: thus, the exposure

to intense Iight made the colours of the daylight fluorescent paint samples whitish.

Thc srirnplrs cxposed to fluorescent light (the Alternative Settings Exposure experirncnt) hded more slowly

thrin the srimples cxposcd to sunlifht (the Sunlight Exposure expcriment) (Graphs 35.36.43-45).

In the Alternative Scttings Exposure experiment. the UV filters. both the NRS-90 filter and the Shinkolite

filtrr. reduced the fading rate of the thick Utilac Fluorescent Red samples. but the UV filters did not retard

the fadins of the thick Wallrick's Fluoresccnt Orange (Graphs 46-49). The fading rrite of the thick Utilac

Fluorescent Red srirnplcs becarnc ripproxirnritely a half by the use of either the NRS-90 tïltcr or the

Shinkolite filter (Table 16).

In the Alternative Settings Exposure experiment. the effect of relative hurnidity was obvious in the fading

of' the Utilric Fluorescent Red srimples: rhe srirnples tested under RH O C / r faded frister than the srimples

tssted under RH 50 %. The effect of humidity on the thick Wsillrick's Fluorescent Orangesamples \vas not

consistent. (Graphs 50-57).

The Step-by-Step Fading experirnent \\.as not complrred. The thick srirnples of Wallrtck's Fluorescent

Oranse achieved three prsdetrrmined peak heights, 90 %, SO /7c and 70%, of the originals ris they faded, but

they did not achieve 60 52 of the original during the rxperimental period. The chin samples of Wallrick's

Fluorescent Orringe achieved tivo predetermined peak heights. 90 9 and SO Q of the originals as they

faded. but 70 '7c and 60 57c of the originals have not been achieved during the experirnental period.

For thc Sunlight Exposure experirnent, the sensitivity of the integrating lightmeter was reduced to 1/33 as a

result of the modification. and the light dosage on the samples was calculated using the factor 32. The

integrating lightmster was used frorn 13:00 hrs. on September 17. 1999 to 13:35 hrs. July 7.2000. The

modified integrriting Iightmeter was installed about two months after the stan of the experirnent: by this

tirne. th<: samples had alreridy faded considcrably. The sum of the light energy received by the samples was

ctpproxirnately 41.52 mega iux hours for 292 days and 2 3 3 hours (703 1.5 hours), excluding the short

breaks for the mcasursments. and also exc lud in~ the period bsfore the sensor modification. The total period

of samplr exposure was 357 driys and 6.5 hours (8571.5 hours).

Graph 12 1 shows the estimatsd sunlight dosage on samples against the actual period of sample exposure.

The accumulated sunlight dosages were estimated based o n the readings o n the integrating lightmeter with

assumprions that the integrating lightmeter hrid reset itself either once o r twice every week until its sensor

wris rnodificd. After the ssnsor moditlcation. the readings o n the integrating lightrneter were multiplied by a

factor of 32. and wrre added to the estimated values of the accumulated sunlight dosage before the

modification. Graphs 122- 1 2 1 and 126- 128 show the fading rates of the Sunlight Exposure experiment

samples agriinst the estimate o f the accumulated sunlight dosage when the integrating lightmeter reset once

ri I V S L ' ~ . Grriph 125 shows the fading rate of a thin Wallack's Fluorescent Orange sample against the

estirnate of the accumulated sunlight dosage when the inteerating Iightmeter reset twice a week.

For the Alternative Settings Exposure expcriment. inside o f the glass charnbers. the totai light dosage was

5S.21 mega lux hours. and the total UV dosage was 13.10 watt hours per square rneter for 382 days and

17.5 hours (91 S5.5 hours), excluding the breaks for the measurements and the power-offs conducted by the

institution. The average light intensity was 6.34 kilo lux and the average UV content was 225 micro watts

per lumen. borh inside of the g l a s charnbers.

4. 1. S. Discussion

As was alrrsidy mentioned in the "Results." ri thin Liquitex Fluorescent Orange sampie, LFOr03, faded to a

grcater extent than did LFOrû 1 and LFOrû2. although these three samples were exposed io sunlight under

the same conditions. When these samples were prepared. LFOrû3 appeared to be thinner than the others.

Probably LFOrû3 was actually thinner than LFOrOl and LFOd3, and this caused LFOrû3 to fade faster

t h m others (Graphs 2 1-22).

In the Alternative Szttings Exposure experiment. the thick Wallack's Fluorescent Orange samples and the

thick Utilric Fluorescent Red sarnples showed different reactions to their cnvironrnents upon light exposure:

rht. varyin2 relaiivc humidity lrvzls and UV filters did not affect the fading rate of thc Wallack's samples.

whilr the Utilac sarnples drrnonstrated appreciably diffrrrni fading rates d u e to the different relative

humiditirs and the different UV filters used. The difference in the pigment cornponents rnay be rhc cause o f

thc different rcactions to thcir environrnrnts betwern the Wallack's Fluorescent Orange sarnples and the

Liquitcs Fluorescent Orange samples. but it rnay be becausr the thick Wallack's paint tilrns wcre not dried

enough. During the sample preparation. it wris observed that an unexposed thick paint film lost its opacity

during the experiment period. The thick Waflack's paint samples were allowed to dry oniy for one wcek

before the Alternative Settings Exposure exprriment started: probably o n e week was too short for the paint

films to equilibrate to the ambient relative humidity. (More details are discussed in the section of

"Suppkmentril Information About the Experirnental Settings.") Utilac spray paints are oil based. therefore.

the solvent in a Utilac spray paint evaporates more quickly than the solvent in a Wallack's acrylic paint that

is wttt'r based. Probribly the thick Utilac prtint sarnples werr dry enough when the experirnent staned.

Contrary to this. it is likely that the thick Wallack's Fluorescent Orange paint film stiII contained water that

interkred with the fading of the samples by refracting o r by absorbing light during the experiment.

although the diffrrence in the pigment components must be investigated before concluding-

The hues of the fluorescent paint samples became more yellowish a s the paints wcrc damaged by light.

This phenomena has bscn already reponed by Cowling. and hue shift seerns to be a common aging process

arnong fluorescent p igr~ents (CowlingJ-S.. e t al. 1959) (EI1is.M.H.. e t al- (1) 1999).

The results of spcctrophotometry on the fluorescent p i n t sampIes showed significant d e c r a s e of the

dominant peak heights. elevation of the uoughs, and slight shift of the dominant pcak wavelengths. These

resultr agreed with the results learned from visual observation: loss of saturation and hue change. The

saturation of a paint colour decreases as the dominant peak becornes Iower in the reflectancc curve. The

Lightncss dccreases as the total amount of reflcction, corresponding CO the size of the area below the

- 93 -

reflectrince curvc. diminishes. The hue changes when the configuration of peaks changes: when the

v.avelrngth of a main peak changes. when the balance between the dominant peak height and the other

parts of thc reflcctance curve changes. or whrn another major peak appears.

The elevation of trough irnplies that the pigment has lost its ability to absorb light. If the trough includes

the excitririon waveltsngths. this furthrr impfies that the pigment has lost its ability to produce fluorescence.

A fluorescent pigment absorbs light at shoner \vavelengths. converts it into a lower rnergy light and re-

emits ir at lonser wavelengths. If a fluorescent pigment absorbs less light at a short wavelength region,

more Iisht wiiI be reflected at the short wavelength region. and less tluorescence wiIl be emitted at the high

wrtvelength region.

Besides rhe hue differcnce. the Liquitex Fluorescent Orange paint was more opaque and less viscous than

the Wallack's Fluorescent Orange paint. Regardlas of the Iower viscosity, the Liquitex paint built up more

quickly. shrunk less in the drying process. and achieved a t o u c h - d l srate faster than the Wallack's priint-

Probably the pigment in the paint was more concentrated in the Liquitex paint than in the Wallack's paint.

The former may have contained a non-fluorescent pigment as a toner (Srnith,T. 1982). Probably the

Liquitex paint contained less water and less colloidal substance (gel) that uaps water in the medium. and

this may bc the reason why the Liquitex paint dried frister than the Wallack's paint did.

The Wallack's acrylic fluorescent priints used in these experiments are student grade. and so they mriy not

best represent the category of daylight fluorescent paints used by artists. Nonetheless. this does not mean

that the pigments used in the Wallack's paints are less stable than the pigments in other brands. because

fluorescent pigments are nor considered to be permanent nor archiva1 grade (Berthe1.B.). The Wallack's

fluorescent acrylic paints were suitable for this study because they did not contain toners nor opacifiers. as

this was confirmed by the manufacturer (BogstadtC). The Liquitex Fluorescent Orange paint used for this

study apperired to be opaque and it possibly contained ri toner. The toner misht have strengthensd the

lightfastness of thc Liquitex Fluorescent Orange paint. Due to the absence of toner and opacifier. the resulfs

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of the expr imen t with the Wallrick's fluorescent priints correctly retlectcd the agcing characteristics of the

pigments in the paints.

AI1 colour measurements in this experiment w r e conduçtsd borh with and withour the ultraviolet ponion in

the illumination. and the reflectance spectra with and without the ultraviolet portion wtxe comparrd. T h e

U V filter in the Spectrogard I I \vas found to have no influence on the reflcctance spectra of the sarnptes

(Grriphs 3-6). The UV filter cuts off ultraviolet light belou. 400 nm (Graph 1). Although the dit'frrsnce in

the illumination's power distribution specua with and without ultraviolet light is small, (Graph 2) i t is

certain that the excitation light in the visible region was intense enough to rnake the sample paints

tluoresce.

T h r irrsgularities of curves at the Nh day (August 17. 1999) and a t the 27sh day (April 17.2000) on

oraphs 3 1-42 were considered to be errors with the spectrophotometer. b

4. 1.6. Conclusion

Daylight tluorescent pigments. especially those sold a s paints for artistic use. lose their colours much more

quickly than non-fluorescent paints do. when they are exposed to intense illumination. As a result. dayIight

fluorescent pigments chanse their visual apperirance much more quickly than non-fluorescent pigments do.

Thc use of a UV filter is effective to reduce the fading rate of daylight fluorescent pigments. A varnish with

ri UV absorbing agent may have a similar effect. but more study is necessary in this area.

This expcriment s h o w d a good consistency with the literature in terms of the Stokes shift, and the fast rate

of pigment colour fading. Another study is necessary to see if fluorescent pigments actually gain colour

intrnsity in the eariy stages of deterioration duc to light exposure.

11 is important to notice that the appearance o f daylight tluorescent pigments is extremely diffcrent from

non-fluorescent pigments bec;1use fluoresccncr has complicrited visual effects. Colour measurement is a

useful rncthod 1 0 understand the optical propenies o f pigments, especialiy whcn fluorescence is invoived.

4. 1.7. SupplementaI information About the Expcrimental Settings

The i n t e p r i n g lightrneter used in the Sunlight Exposure esperimeni did not have sufficient memory to

integrrire thc direct sunlight dosage for many weeks. It was a problem because the experiment site could not

be accessed frequently and daily monitoring o f the integrating lightrneter w;is not possible. The integnting

!ightrnctsr wrts drsigned to monitor the indoor environrnent o f rnuseums. In many rnuseums. the

illumination Ievel is kept low and direct sunlight is blockrd in ordrr to protect the objecrs in the building.

therrtore, rin indoor tbpe integrriting lightmeter does not rsquirs a Iarge capacity. Sunlight was too intense

for this type o f instrument and the instrument kept on rrsetting itself in a short cycle as it hit the maximum

rivailable figure. This instrument docs not Icavs a record nor stores memory. The problem o f short cycle

rcsetting \vas discovered about one month after it staned operatine. The problern took time to be found

because the pruject svolved 3s i t proceeded and it was impossible to anticipate the difficulties in advance.

Aticr the problern wris discovered, the sensor o f the integrating lightmeter was covered with aluminium foi1

ivith ri srnrtll hole in the centre. This aluminium cover reducsd the arnount o f light that hit the sensor. The

intqrrtting lightmeter's count was reduced to 1/32 of the rertl value, allowing the instrument to kerp

recording light dosage for a much longer period of time.

In order to compensate for thc loss of solar radiation data during the first two months of the Sunlight

Exposure experiment. an external source of data was sought. It was anticipated that the n e c e s s q data

couid be purchased from the Environment Canada. a Canadian govzrnmental organisation: however. it was

discovcred that the data was not available. Other sources of data were not found by the completion of this

thesis.

iMuscunis sometimcs use dritriloggcrs ro monitor the indoor environment. A datalogger receives inputs frvrn

sensors and stores the data in its mcrnory or deposits the data into ri computer connected to it. It would have

been dcsirrible to use a datrilogger for this projeci to rnonitor the light intensity. the UV content. the

ternperciiurs of the samples and thc relative humidity around the samples. but the equipment upas not

availabls for this project. A surtrtce temperature sensor and a humidity probe also would have been helpful

for ihis project. but they were not rivailable.

The fluorescent light box used for the Alternative Settings Exposure experiment was shut down for short

periods o f time once in a while. The reasons for the power outage were a building maintenance operation

and rinother experiment conducted in the same room that required darkness for the on-site samplr

rneasurcmsnts.

Colorimetry cm be done either by including the specular cornponent (specuhr reflection) o r by excluding

i t . Usurilly. ir is included at the Canadian Conservation Institute. Ho\vever. in a trial colorirnetry run for this

projrct \cith the Spectrogard II. when the specular cornponent was included, the reading o n daylight

tluorsscrnt paints exceeded the instrument's upper detection limit, and therefore i t wris necessary to

measure the colours by excIuding the speculrir component. S o far. there is no way to teIl the consistency of

the results whsn the specular componsnt is included and when i t is excluded, in the colour rneasurement o f

day light fluorescent pigments.

The light exposurc settings adopted in this experiment were different from the settings recornmended by the

ASTM. The equipment recornmended by the ASTM was not available for this study because o f spatial,

time. and budgctary rcasons. The results o f this experiment should not be subjected to a direct comparison

with results from studies conducted under the ASTM recommendations.

The watrr in the paint film rnatrix is suspectcd to have affected the fading rate o f the thick Wallack's

Fluorcsccnt Orangc paint samples. Thosc samples rnust have k e n insufficiently dried because the

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opaqucness of the unexposed sarnples changed as the time wsnt by. The thick Wallack's samples were

prcparcd by building up paint Iriyers on a white card that has a black border for paint opacity test. and the

painr \vas judged to be thick enough and opaque enough when the black border wa'; completely obscurçd.

Thcsc thick Wallack's Fluorescent Orange paint srirnpIes were tirst prepared as a large paint film. and the

large paint film was trirnmed to obtriin severaï srnall samples. The remnant o f the large film was kept for rt

latcr refcrence. The black border contained in the rcmnant shawed through a few weeks later. although it

had been completely invisible when the sample preparation \vas completed. The thick Utilac samples %ers

prepared in the sarne rnanner. and the black border of the substrrite re-appeared every time the paint dried.

but the final product of the h ick Utilac paint film did noi iose its opacity as much as the thick WalIack's

paint film did.

The Stsp-by-Step Fading experirnent was not completed partly because of the timt: constraints and prirtlj.

becriuse of the change in the environrnent for the project. The first supervisor for this research w u a

painting conservator who planned to include experirnental inpainting o f the faded samples as a part of the

projrct. After the passing away of the tirst supervisor, who could execute inpainting as a professional

painting conservator, this parr of the project had to be abandoned.

Choices of materials for srimplcs were constrained by cime and budget. The Wallack's acrylic paints were

donrited by a friculty rnember for this project. The Liquitex Fluorescent Orange paint and the Utilac

Fluorescent Red paint were chosen because they represented the category o f rinist paints and the category

of spray paints for exterior use (expected CO be lightfast), respectiveiy, among daylight fluorescent orange

paints available in Ottawa when the project started to run. Only a few brands o f daylight fluorescent acql ic

paint were available for artistic purposes in Kingston and Ottawa. In the same area. one brand of

watercolour (Windsor & Newton). two brands of spray paint, a few brands o f airbrush liquid, and one

brand of textile paint were available with daylight fluorescent colours. One brand of paint with synthetic

media was availabIe in a phosphorescent colour. A few types of hobby colorants wcre offcred as glow-in-

the-dark materials.

At the Canadian Conservation Instituts, a11 Iaboratories arc locsted inside of the security zone where

unauthorizcd access is prohibitçd- The environment for the SunIight Exposure expcrirnent uas set o n the

south fxing window in room 232B. and the environmcnr for the Alternative Settinzs Exposure expcrirnent

was locatsd on the mezzanine o f room 124. Room 232B was on the second tloor. facing a wide sprice

outside. and the window hrid a narrow roof, a thin column on one side. and ri narrow sill. Room 121 \vas 3

Iaboratory for many long-term rxpcrirnents, and acccss to the roorn was restricted from tirne to time

because of the nature o f the projects in progress. The room hrid no window, and the roorn light was turned

on and off but the ambient lighting conditions did not affect the light intensity in the fluorescent light box.

This was confirmed through occasional rneasurement o f the light intensity and the UV Ievel at regular

points inside the fluorescent Iight box-

The Sunlight Exposure experimrni started on July 14. 1999. The Alternative Scttings Exposure experiment

and the Step-by-Step Fading experimsnt staned on July 30. 1999. The SunIight Exposure cxperimrnr was

terrninated on July 07. 2000. The Alternative Settings Exposure expsriment and the Step-by-Srep Fading

experirncnt werc terminated on August 17.2000.

4.2. Analysis of Optical Properties: measurement of the excitation wavelengths and the fluorescence wavelengths

4.2. t. Objective of This Esperiment

The colours of daylight tluorescent pigments \vil1 be better understood if the colour of tluorescence and the

colour of retlection are studied seprirately. The knowledge of the relationship betwrrn the excitation

radiation and the colour of daylight fluorescent pigments will hslp conservators choose the bsst

illumination for conservation treatments and exhibitions of driylieht fluorescent materials. This experiment

\\.as perfurmed to determine the excitation wavelengths o f daylight fluorescent pigments and the

contribution o f fluorescence to the perceived colours of the daylight fluorescent pigments.

4 - 2 2 . Espcrimental Set Up

Outline

In this experiment. three differrnt types o f spectrophotome~ric measurements were taken for each daylight

fluorescent pigment sample: a visible range reflectance spectrum with daylight type illumination

(Reflectance Spectra). ri spectmm of emission power distribution as a function o f excitation wavelength

scanned through the visible range (Excitation-Emission Spectra). and a visible range reflectance spectrum

excited by monochromatic illumination at three selected wavelengths (Monochromatic Excitation Spectra).

The specimens for this experiment were the sarnples used for the Accelerated Fading experirnents and six

other colours o f pa ins thrit werr newly obtained.

Samplc Prcparation

Kt3w srirnplcs \vert: made with r1rvt.n colours of priint: Wdlrick's student acrylic paint Lemon Yellow

(coded ris WLYa), Wsillack's studsnt acrylic paint Fluorescent Yellow (WFYa). Wallack's student acryIic

paint Fluorescent Orange (WFOri). Wallack's student acrylic priint Fluorescent Magenta (WFMa). Liquitex

Concentratcd Anist Color acrylic Fluorescent Blue (LFB2ri). Liquitex Concentrated Artist Color acrylic

Fluorescent Green (LFG25i). Liquitex Concentrated Artist Color acrylic Fluorescent Ycllo~v (LWLA) .

Liquitcx Concentrated Anisr Color acrylic Fluorescent Orange (LF02a) . Liquitex Concentrated Artist

Color acrylic Fluorescent Red (LFFUa). Liquiteiu Concenuated Artist Color acrylic FIuorescent Pink

(LFP3a). and Jacquard Textile Color Fluorescent Violet (JR7a).

The new samples werc made by mzans of tape rnoulding: each srtmple paint was spread bet\vsen parailel

masking tape blockades on a card. Each blockade consisted of two Iayers of masking tape. The substrate

card \\.ris ri papcr for watercolour painting. Arches (Hot Pressed. 1 SS grs). The paint sarnples were dried in

the open air for one day and trirnmsd. Masking tape was rsmovrd from the card after the paints dried. but

the space under the masking tape \vas Ieft attached to the samples as handling mrirgins. The area of paint

film tvris 2.5 cm x 8.0 cm for each sample. and the handling margins were on both sides of each sample

dong its Iength. The Wallack's acrylic paint base. a component of paint medium, w3s aIso prepared in the

same manner (WBSa). A list of samples is attsched (Table 1 1 ).

The Reflectance Spectra. the first type of mcasurernent, were taken for al1 samples. paint base. blank

Arches paper and the white space of an ASTM form 3B for paint opacity test (3BOl). The Excitation-

Emission Spectra, the second type of measurement, were taken for aII srimplss on Arches paper. pain[ base

on Arches paper. blanic Arches paper (arches) and the white pan of a blank ASTM form 3B. The

Monochromatic Excitation Spectra. the third type of measurement. and the Excitation-Emission Spectra

were taken for both faded (exposed) and not faded (unexposed) samples of the preceding experimenis, the

Sunlight Exposure and the Alternative Ssttings Exposure. The substrates for those samples were ASTM

torm 3B.

Reflcctancc Spectra

The retkctrince spectra of the sarnples were taken in the regular manner with the scanning

spectrophotometer. the Spectroprird II Color Systern (BYK-Gardner). as was done in the Accelerrited

Fading expsriment. T h e illumination type was D6500 in the C E standard, a daylight type. The 10 degrees

observer in the CIE standard was chosen, and the specular cornponent (specuIar reflection) was exctuded.

For this esperiment. ultraviolet light between 380 nm and JO0 nrn was always included in the illumination.

In the Accrlcrated Fading study. it was provcn that the excitation a t 380400 nrn does not make a difference

to ci rellectancc spectrum obtained usins the Spectrogard II Color System.

Escitation-Emission Spectra

The excitation-emission spsctra werr taken using another type o f scannins spectrophotometer. the Cary 3

(Varian). The Cary 3 rneasures absorbante and uansrnittrince o f transparent sarnples as its basic function.

but it d s o msasures rsflectancr when an inirgrving sphers is attached in the sample compartment. thus. the

Cary 3 can measure the surface colours of opaque sarnples. Unlike the Spectrogard II. the Cary 3 divides

the illumination into monochromatic rays using a monochrornritor before the light hits the sample. detects

the light ernitted from the sample surface, and indicates the total light intensity of the sarnple surface for

erich monochromatic illumination.

The monochromator o f the Cary 3 scans through the wavelengths from 800 nrn to 200 nm, including the

visible region and the uluaviolet region o f the electromagnetic energy spectrum. The light sources in the

Cary 3 were a QI Iamp (quartz halogen Iarnp) for the visible region and a D2 Iarnp for the ultraviolet region.

In this cxperiment, the illumination for merrsurcment is callrd the excitation light and the light intçnsity

mrcisured on rhc sarnple surface is called the emission. For non-fluorescent sarnplrs. an emission value

equds the reflcctance rit erich excitation wavelength. For fluorescent samples. the reflection at the

excitation wavelength and the fluorescence induced by the monochromatic light at the excitation

\vavelcngth combine to form the total emission. regardless of the wavelength o f the tluorescsnce itself.

hlonochromtic Excitation Spcctm

The Spcctrogard II was modified at the Canadian Conservation Institute (CCI) to examine the

monochromatic excitation o f fluorescent piernents. In order to select the excitation wavelength, an

initrference tilter \r+ith a specific bandpass wris insened bçtween the illumination source and the integrating

sphcrc of the Spectrogard II \vhrn the reflectance of a sarnple was rneasurcd. The interference filter \vas

removed ~vhen the reflectance of the reference (the white interior of the integrating sphere) was rneasured.

The prirarncters of rneasurement were the CIE ILL D65 (daylight type) illurnination with ultraviolet light.

the CIE IO degrecs observer, and the speculrir component (spscular reflection) excluded. The Spectrogard

I I \vas crilibrated in the regufrtr manner without an interference filter-

Facility and Location

Sample prepriration and al1 three types o f measurements were undenaken at the Canadian Conservation

Institute (CCI) in Ottawa. Ontario. Canada. In the entire buiIding o f the Canadian Conservation Institute,

the temperature and the relative humidity are conuolled to approxirnately 22 OC and 50 %.

The Excitation-Emission Spectra of three difkrent types of tluorescent orange samplés are presented in

Graphs 33-60. The spectra were compared arnons exposed (IO light) and unrxposed samples. The

excitation-Ernission Spectra o f the paint samples and the substrate materials are cornpared in Graphs 6 1-7 1.

The Monochromatic Excitation Spectra of the standard white crrctmic tile and the prrint sarnples are

presenred in Graphs 72-S6. Table 14 presents the data that numsrically describe the emission from the paint

samples excited by three differrnt rnonochrornatic illuminations. Table 15 presents the data that were usrd

to calculate the paint sarnples' tluortscence inftnsity induced by thres different monochromatic

illuininations. The Reflectance Spectra and the Excitation-Emission Specrra are compared for each sample

and for rrich substratc material. and rire presented in Grriphs 87-1 13.

4. 2. 4 Discussion

Acronyms of sarnple narnes a re repeated here for the convenience o f readers:

IFV: Jacquard textile colour Fluorescent \'iolet LFBî,: Liquitcx acrylic Fluorescent Blue LFG3: Liquitex acrylic Fluorescent Green LFYZ: Liquitex acrylic Fluorescent Yello\v LFO: Liquitex acrylic Fluorescent Orange for the accelerated fading test LF02: Liquitex acrylic Fluorescent Orange newly obtained LFR2: Liquitèx acrylic Fluorescent Red LFP3: Liquitex acrylic Fluorescent Pink WLY: Wallack's acrylic Lernon YeIlow WN: Wrillack's acrylic Fluorescent Yellow IWO: Wallack's acry tic Fluorescent Orange

Oenta WFM: Wallack's acrylic Fluorescent Ma, WBS: Wallack's acrylic paint base UFR: U d a c spray for inreriorkxtcrior Fluorescent Red 3B0 1 : blank ASTM form 3B arches: blank Arches paper a: intcrrnediate thickness of paint o n Arches paper r: thin paint layer p: thick paint laycr

The Excitation-Emission Spectra wrre alrnost rhe same among sampIes with the samc parameters such as

solour and the extrnt of light cxposure the sarnples received. .As was the case for the Accelsrated Fading

experirncnt. the excitatifin-emission spcctrum of a thin Liquites Fluorescent Orange sarnplc. LFOr03.

indicated 3 p a t e r cxtent of fading cornparcd to other sarnplrs of the sarne kind, LFOrûl and LFOr02

(Graphs 5s-60). The Reflectance Spectra and rhs Excitation-Emission Spectra of stimplrs rire çompared

arnong difkrent paints and substrrires. and cire presented in Graphs 6 1-7 1.

Prior tu the measurernent of the Monochromatic Excitation Spectra with the Spectrogard II. the bandpasses

o f the interference filters were checked using the standard white cerarnic tile. For the fiIters with

bandpasses of 4OO nrn. 450 nm and 48s nm. rhe reflectance peak appeared at 300 nm, 350 nrn and 390 nrn

rtspectively, and their peak hsighrs were S. 19 ?. 17.22 5 and 7.24 G in the srime ordcr. The peak of the

Iast filter appeared rit 390 nrn becsusc the Spsctrogard 11 rneasures reflectance rit each 10 nm. therehre. it

does not sense the reflectance at 438 nm. (Graphs 72-75).

In the merisurement of the Monochromatic Escitation Spectra. the sarnples received only a pan of

illumination through the interference tïlters. thsrefore. the data obtained using the interference tïlters could

not be compared with the data obtained through regular measurements. Factors were calculated from the

rr'tlectance values of the standard \r.hite ceramic tile ivith and without the interference filters (Table 14)-

Graphs 76-86 are the results frorn the monochromatic excitation o f the paint sampIes at 400 nm. 450 nm

and 488 nm. The peaks are considered to represent fluorescence induced by the monochrornatic light chat

illuminatsd the samples. By multiplying with the factors in the Table 14. and by using the monochromatic

excitation curves of the standard white cerarnic tile as a baseIine for individual excitation wavelengths. the

emission peak heights in the graphs were converted to data compatible with the data frorn the regular

rncasurements. and presented as the "tluorescsnce as % reflectance" in the Table 15. This table shows the

estirnrited contribution o f fluorescence to the total reflectance excited by each monochrornatic light. for

c.uarnplc. the sample WFOrOS (Wallack's Fluorescent Oranse. thin. not exposed IO sunlight) hris an

- IO5 -

crnission psak at 610 nm that is excited at 400 nrn. 350 nm and 488 nrn. The sum of the ernission at 6 10 nrn

cscitcd by monochrornatic illumination with wrivelengths of 400 nm. 450 nm and 488 nrn e q u d s the light

intensity of a rctlectrince 30.72 '2. Under regular daylight, the tluorescence intrnsity will be higher becausç

daylight has ri continuous powsr spcctrum betiiwn 400 nrn and 488 nrn. and because a driylight fluorescent

p i p e n t is excitrd at each wavr lengh through the excitation wavelcngth band.

.A thin lViillrick's Lemon YslIou srtrnple. WLYrO5 (not esposed [O sunlight) has an emission rit 5 10 nm thrit

is excitrd rit 450 nrn. It is not clear whcthcr this emission is fluorescence o r an crror. No significant

fluorescence emission is recognised when the Reflectance Spectrum and the Excitation-Emission Spectrurn

of the thin Wrillack's Lemon Yellow srtmple are compared (Table 15. Graph 76).

Grriphs S7-88 show the Retlectance Spectra and the Excitation-Emission Spectra of blrink substrates that

nue ASTM form 3B and Arches paper. Thesr blank forms are expected t o be non-fluorescent. regarding

their applications intended by the rnanufacturers. and their excitation-ernission enerzy must consist solely

of rcflection. therefore. the Retlectance Spectmm and the Excitation-Emission Spectrum of the same

material rnust match. The difference between the Reflsctancr Spectrum and the Excitation-Emission

Spcctrurn on the graph of the same material results frorn the difference between two instruments used for

the rnerisurernents. If this difference is corrected with a factor. the cornparison between the data obtained

using the Spectrogard I I and the Cary 3 becornes reliable. The factors for ASTM form 3B and for Arches

priper wrre calculated by averaging the difference o f the Reflectance Spectra and the Excitation-Emission

Spectrri between 400 nrn and 720 nm. The factor to correct the reflectance of ASTM form 3B was 1.045,

and the factor for Arches paper was 1.057. Thess factors were applied to correct the Reflectance Spectra o f

ri blank -4STM forrn 3B and a blank Arches paper. As a result. the factors were found to be feasible for

correcting the Spectrogard Il's Reflectance Spectra between JO0 nm and 720 nm in order to compare it to

the Excitrition-Emission Spectra obtained with the Cary 3 (Graphs 69-90).

Grriphs 9 1 - 102 show the Excitation-Emission Spectra and the corrected Reflectance Spectra of the sarnplcs

t'rom thc Sunlight Exposurr expsrimcnt. Grrtphs 103-1 13 show the Excitation-Ernission Spectra and the

corremci Rctlcctance Spectrri of the samples prepared on Arches paper (no light exposure). The factor

1.015 \\.as applied to the former set of sarnples since their substrate was ASTM forrn 3B. and the factor

1 .O57 uas applied to the latter set of samples thrit were prepared on Arches paper.

On Graphs 9 1- 1 13, the approximats contributions of fluorescence to the total retlectance of the priint

samples u n be visualised. At uavelengths around and higher than the dominant reflectance peak, the

illumination doc-s not excite fluorescence, therefore, an Excitation-Emission Spectrurn at this region

approximates a sheer reflectance. A Retlectance Spectrum at the wavelengths much lower than the

dominant psrik mostly consists of reflection. The difference bstween the Reflectance Spectmm and the

Escitation-Ernission Spectrurn of a sarnple rit a high wavelength region reprcsents the energy of

fluorescence smitted at each wavelength. The difference betwssn the Excitation-Ernission Specuum and

the Retlectrince Spectrum at a low wavelen@ regions represents the energy of illumination that is

consurned to fluoresce.

The Retlsctance Specrra and the Excitation-Emission Spectra of subsvates and paints are cornpared on

Grriphs 01-7 1. The excitation wavelengths of the sarnple paints can be dcduced frorn Graphs 67.69, and

9 1 - 1 1 3. The WalIack's Fluorescent YeIlow sample, the Wrtllack's Fluorescent Orange sarnple and the

Wrillack's Fluorescent Magenta sample are excited by the portions o f illumination ranging from about 400

nm up to the dominant reflectance peak wavelength. The Wallack's Fluorcscent Ycllow sarnple and the

Wallack's Fluorescent Orange sample are ais0 excited by ilIumination between 280 nrn and 300 nm. The

Wrillack's Fluorescent Magenta sarnple has two dominant reflectance periks. The excitation wavelcngth for

the lower reflectance peak cannot be specified from Graph 98, but on Graph 106, the Wallack's Fluorescent

Magenta sarnple is excited by illumination at 280-320 nm. The emission from the Wallrick's paints caused

by the illumination below 250 nrn is the ernission frorn the paint brise but not frorn the pigments. The

Excitation-Ernission Spectrurn of thc Wallack's paint base is presented on Graph 65.

On Grciphs 67 and 69, most fluorcsctm paint samples (except for the Wallack's Fluorescent Orringc

scirnplcs) show low Excitation-Ernission around 350 1 30 nrn. This means illumination with wavslsnpths

350 t 30 nm do not cause colour in thesr tluorsscent paints. On the one hand. the ultrriviolet portion of

daylifht is approxirnatcly 300400 nrn (Sinsh.N. 1999. p.38) (Q-Panel Company. Bulletin L-S 16). on the

other hrind. the visible ponion of driylight clin excite driyli~ht tluorescent pigments without the ultraviokt

portion, 3s this was proven in the Accelerated Fading project. It can be concluded that for sc.-ne daylight

tluorescsnt pigments, a UV filter with a cut-off point between 380 nm and 300 nm provides a protection

against darnrige from ultraviolet light while allowing the pismens to emit appreciable fluorescence.

The Liquitex and the Jacquard tluorescrnt paints on Arches pliper are excited by illumination st the

\vavelengths immediately below their reflectance peaks as are the Wallack's fluorescent paints. In addition

to the excitation ranges in the visible rcpion. the Liquitex Fluorescent Yellow sarnple, the Liquitex

FIuorescent Orange sample, the Liqu1te.u Fluorescent Red sarnple and the Liquitex Fluorescent Pink srirnple

have their second excitation peaks around 260 nrn and 390 nrn. The Liquitex Fluorescent Blue sarnple and

the Liquitex Fluorescent Green sample have excitation peaks around 260 nrn. but the Jacquard Fluorescent

Violet srimple does not have a si~nificant excitation peak brtwsen 200 nrn and 300 nm.

As the graphs show, the Liquitex Fluorescent Blue paint and the Liquitex Fluorescent Green priint absorb

relativcly srnall amounts o f light and discharpe rather small arnounts of fluorescence comprired to the

Liquitex Fluorescent Yellow, Orange, Red and Pink paints. As a natural consequence, the reflectance peak

of the Liquitex Fluorescent Blue paint and the Liquitex Fluorescent Green paint are smdI cornpared to

other tluorescent colours This is why thcse blue and green fluorescent paint colours are Iess intense than

0 t h fluorescent paint colours, such as ycllow. orange, red and pink.

4. 2. 5. Conclusion

Thr: spectrophotometric reridin; o f the total rstlectrince consists of reflectance and fluorescence \ \ .hm ri

daylight fluorescent pigment is mr:lisured. By rneasuring the h.Ionochromritic Excitation emission. the

contribution of fluorescence 10 the total retlectlince crin be estimated. In order to estimate the ratio of

fluorescence in the total reflectance of a daylight fluorescent pigment. the entire excitation wavelmgth

r q i o n o f the pigment must be scanned by a rnonochromator continuousIy.

An Excitation-Emission Spectrum offèrs important information to determine the excitation wavelengths of

a driylight fluorescent pigment. ilThen combined with a Retlectance Spectrum. rin Excitation-Emission

Spwtrum indicates the escitation \vavelzngths and the fluorescence wavelengths of a driylight fluorescent

p i p e n t mors prccisely.

4.3. Identifying Daylight Fluorescent Materials

4.3. 1. Objectivc of This Esperiment

I r might be good for a conservaror to know \\ htthrir or not the materiais of an objrict are fluorescenr. Such

knoukdge clin affect the choicc of the conscirvrition trrritmenr tvhen the conscrvator pcrforms a

conserva~ion trçatrnent on the objsct. Thus rhis experimenr \\.ris implcrnented to find methods for

distinguishing daylight tluorescent mareririk from non-fluorescent materials.

4.3.2. Experimental Set Up

Outline

Colour rnsasurernent \vas performcd on various types and colours o f paper and their reflectance s p e c m

\\.rre compared. The sarnples \ v t x â1so observed undrr a UV Iamp and the colours of their fluorescence

\rwe recorded. The results of the colour r n e ~ ~ e r n r n t and the observation under UV Iarnp Lvere cornbined

and anrilyscd to discovsr the charricteristics that are common among daylight fluorescent materials.

Sample Preparation

Three differenr types of paper \vue used ris samples: Astrobnghts (Wausau Papers. Canada), Origarnis

(1'0yo CO.. Japrin), and envelopes (manufacrurers unknown). Several colours were chosen as sarnples frorn

each type of paper. The samples were trimrnsd to sizes appropriate for colour rneasurcment. Blank

photocopy paper, a blank ASThl form 3B. blank Arches paper, Wallack's acrylic paint base on Arches

priper. the WaIlack's paint samples on Arches paper. and the Liquitcx priint sarnplcs on Arches paper were

alw obscrved under the UV larnp. A list of sarnplcs is attached (Table 12).

Facility and Location

Sarnplr: preparation and cduur musurement tvere conducted at the Canadian Conservation Institute (CCI)

in Ottti\vri. Ontario. Canada. In the cntire building of the Canadian Conservation Institute, the temperature

and the relative humidity rire controlled to ripproximately 22 "C and s'O %. The spectrophotorneter

Sptxtrozard I I *as uscd for the culour merisurement. The tluorescence of the samples was observed undcr

3 Ui' lamp in the Master of Art Conservaiion building at Quecn's University, Kingston. Ontario. Canada.

The U\' lamp wris a handheld typc. Spectratine (manufacturer unknown) with two UV bulbs, BLE-

?'>OB/Spctronics. and two fluorescent white light bulbs, BLE95D.

The retlrctance spectra of priper sarnples arc presented on Graphs 1 13-120. The results of fluorescence

observation under the UV lamp appear in Table 12.

4.3.4. Discussion

.4rnonf th:: Astrobrights samples. Terra Green. Cosmic Orange. Rocket Red and Fireball Fuchsia are

tluorescenr. and other colours rire non-fluorescent, as confirmed by the distributor of the paper. Graphic

Resources. On Graph 1 11. the fluorescent Terra Green paper reflects only about 82 56 at its peak while the

Lunar Blue paper and the Sunburst Yellow paper. non-fluorescent samples. achieve 70-75 8 at their

retlectancr pcak. The maximum reflectance of these three colours are too close to distinguish the

fluorescent sampls from the others. On Graph 115. three fluorescent sample, the Cosmic Orange paper. the

Rocket Red prtper and the Fireball Fuchsia paper. exceed LOO % at their reflectance peak. therefore, it can

bc. concludcd thrit these three samples are tluorrscent. The exarnple of the Astrobrights shows that

rct1c.ctance curvcs that do not cscecd 100 52 do nor give clues to determine whethrr or not the materials are

tluciresccnt. nonethrless. a reflectance above 100 is the evidence of fl uorcscence.

L7ndc.r tt UV Icimp. the Terra Green paper (Atrobrights) was obviousIy tluorescent under UV light. Among

orher colours of Astrobrights paper. the Cosmic Orange paper. the Rocket Red papcr and the Fireball

Fuchsia priper, glowing under the UV lamp. \vert. apprirent1 tluorescent. whilc the Gamma Green paper.

the Re-Entry Red paper. the Mars Magenta pciper and the Planstary Purple paper were obviously non-

fIuorcscent. Thus. observation undsr (i UV lamp crin help in identification of tluorescent materids cilthough

it is not always conclusive.

The Celestial Blue paper (Astrobrights) and the Lunar Blue priper (Astrobrights) were rather bright under

UV light although they were intsnded to be non-thorescent by the manufacturer. The UV lamp rmits

visible blur light at an appreciable intcnsity. therefore. the lisht reflected on the paper surface might

contributcd to the brightness of the CelestiaI Blue paper and the Lunar Blue paper: but thesr pripers might

also contriin fluorescent brightensrs with blue tluorescence. O n the one hand. the blue envelope had blue

tluorescence. on the other hand. the white envrlope did not tluoresce and it appeared grey under UV light.

Since the photocopy papt'r had ri blue glow under UV light. it can be concluded thrit the white envelope

does not contain a fluorescent brightener whsrras the photocopy paper does.

There \\.ris a difficulty in distinguishing non-fluorescent yeIIow paprrs. The Sunburst Yellotv paper

(Astrobrights), a yellow Origarni sample and two orange Origami samples exhibited saturrited colours

under the UV Iamp although they did not have the slow that fluorescent materials usually have. in contrasr

to these pripers, the Wallack's Lemon Yellow priint was dark brown under UV light and was obviousIy

non-fluorescent. It is suspectcd that fluorescent dyes and non-fluorescent dyes were mixed to manufacture

those yellow and oranse papers that have highIy saturated colours under UV light. Nonr of the Origami

samples were UV fluorescent o n their reverse sides that are commonly white.

The Liquitex Fluorescent Red paint and the Liquitex Fluorescent Pink paint showed sirnilar orange

fluorescence under the UV lamp. as they showsd similar rctlectance curves and sirnilar emission patterns at

highcr u*rivelengths (Graph 6s-69).

Some pink and purplish rnaterids tluoresced in orange coIours: the Wallack's Fluorescent Magenta paint

tluoresced in pinkish red under UV light. the Firebalt Fuchsia priper (Astrobrights) was reddish orring. and

the pale pink Origami sarnpk showed pastel orange tluorescence. The Jacquard Fluorescent Violet priint

fluoresced in purplish pink. These cases imply that, at a lower wavelengths region (blue region), the

retlectance peaks of these pink and purple colours do not involve fluorescence but the peaks are shser

rrtlectance. therefore. these materials have orange or red fluorescence.

4- 3.5. Conclusion

When the manufacturer of the material is kno\vn. the best \va? to identify a fluorescent material is either by

rsfrrring to the manufacturer directly or by referring to a document that confirms the rnaterial to be

fluorescent. If the manufacturer of the rnaterial is not knou-n. vizwing the material both in daylieht and

under UV light will help the conservator to identify a fluorescent rnaterisl. although it is not always

possible to determine the materid to be fluorescent or non-fluorescent. A reflsctance peak that exceeds 100

k is a conclusive evidence of fluorescence. but the reflectrinci: peak of a tluorescent material can be lower

than 100 Q.

I t musc be noted that being fluorescent under a UV Iamp does not certify the rnaterial to be daylight

fluorescent. Comparing the excitation-emission specuum and the retlectance specuurn may contribute

information to the conservator who is trying to determine whether the materid is UV fluorescent or

dayfight tluorescent.

5. Case Studies and Conservation Suggestions

5. 1. Colour Deterioration of Daylight Fluorescent Pigments, Other Experiments Reported

Conservaturs and scientists have tried to undcrstand how driylight fluorescent pigments fade, so thrit thry

c m choose the most stable type of daylight fluorescent colorants, s o chat they can predict the fate o f the

pigments which they are handhng. so that the? can irnprove the lightfastncss of thc pigments and retard the

fading of the pigments. Othsrs have tried to objsctively dcscribe and control how fluorescence appears to

the vie\vers' eyes. Reports o f such trials have been obtained both through publications and through direct

personal communication. This section introduccs some examples of experirnents that have bsen pzrformed

by conservators and others ta understand the immediate and the long-term sffects of light on daylight

fluorescent pi, ~ m e n t s .

Esperiment 1.

36 April. 1999 - March 2000 (in progress) by ri conservator.

Expcrirncnt: Exposure of Crerites Fluorcsccnt Orange and Richart D 4 3 Red Orange Daylight

Fluorescent to indirect sunlight. HaIf of the arctri of each sarnple \vas covered with a iMylar sheet (a thin

trrinsparcnt polyuther film) and aluminium tape during exposure for two months. then h d f of the aiready

exposed area was covered (three quarter of the 3rtt3 ws covered at this point). and the exposure was

continued. The colours o f samples were visurilly evaluated.

Rcsults: Richart D-43 darkened substantially during the tïrst tmlo months but the increase of darkening

bwveen the third rnonth and the tu'elfth month seemed tu be negligible. This conservator found Createx

Fluorescent Orange to be lightfast, since it hrid shown no noticcable visual colour shift in the actual

application. (Baxtcr.E.J.).

Note: This conservator showcd an exaniplr of a simple and efficient method with which people can

Instruments. comprire lighthstncss o f paints nithout usin, '

Experiment 3.

Octobcr. 1999 (presented) by Ellis. et al.. New i'ork University. N e ~ v York. U. S. A.

Objective: Lightfastness evaluation

Expcriment: T h e first expsrirnent !vas ascslerated aging of six differènt daylight fluorescent colorants

usine a fadeometer. T h e coIorants were five diffrrent printsd lithographie colours from a Funky

Enterprises' poster. and o n e fine art silkscreen ink, Handschy Aurora Red. dating from 1974. The second

expsrirnent was natural light ag ias and heat asing of the Handschy Aurora Red ink under ambient

conditions and anoxic conditions. The colours were evaluated with a radiometer that detects the total

ensrgy cmitted from the srimple surface as retlection and fluorescence.

Results: In the early stage of aging in the fadeorneter. the emission from the samples decreased at the

dominant psak \~favelengths, and then the bottorns of the dominant peaks Lverz broadened. This indicated

that the initial drirkening and the loss o f saturation occurrcd as the colours o f the sarnples faded. Initial

drirkrning and subscquent fading were obser\.sd with al1 materials testsd with the fideorneter. naturd Iight

and heat. The rinoxic conditions did not have a recognisable effect on the fading o f the sarnples.

(Ellis.h.1.I-I.. et al. (1) 1999).

Experiment 3.

October. 1999 (presented) by Ellis, e t al., New York University, New York. U. S. A.

Objrctivs: T o determine the distance bwveen an exhibitton illumination source and an art work with

daylight fluorescent pigments s o that the light damage on the pigments crin be minimised while maintaining

a sufficient illumination level to excite fluorescence from the a n work.

Experiment: Using ri 15 watt light fixture. the a p p r a n c e of the fiuorescent materials wits evaluated at

various distances.

Rcsults: T h e opt imum distance was t u u ro threc mevrs . ( T h e types of the fluorescent materials used

tiw rhis srudy rire unknown) This cwrrsponds ro approxirnately 0.02 \rat& o f ultrsviolct radiation cnergy s t

the ubjcct surface. A calculrition bascd o n a prsceding study showed thrit daylight fluorescent pigments

v.ould darksn significantIy aftsr 1500 hours o f conrinuous expusure to ultraviolet iight rit 0.02 tv3tt.s.

(El1is.kl.H.. et al. ( 1 ) 1999).

Esperimsnt 4.

(Date unknown) by Golden Arrist Colors. Inc.. New York. U. S. A.

Objcctive: To s h o w the rfkct iveness of UV filtering varnish for reducing light damage on daylight

t'luortrsccnt paints.

Experiment: Fluorescent acrylic paints (rhs company's products) were tested under ultraviolet

radiation in a Q U V Weatherometer for 400 hours. In the \seathrromrter. UVA35i bulbs generated

ultraviolet lisht that simulrtted the ultraviolet portion o f sunli@ filtered through a window glriss. T h e

colour change o f paints with and without h1S.A Varnish (the company ' s product) were comprired.

Rtsulrs: T h e paints without varnish lost chroma and turnsd to a muted brown. T h e varnished paints

darkened to some extent. but they retained the high chromas that a re unique to those paints. (HriyesJ.).

Espcrimcnt 5.

August. 1959 (published) by Cowling. e t al.. U. S. Naval Research Laboratory, Washington, D. C.. U. S. A.

Objective: To find the best high visibility priint for aircraft rnrirking t o prevent mid-air collision and to

riid rcscue operation.

Experiment: Reflectance spectra of a daylight fluorescent paint and a non-fluorescent paint in similar

hues (orange) \vere compared rhrough spectrophotometry. Also. sin orange daylight fluorescent paint was

subjected to sunlight deterioration and the colour change was monitored with spectrophotometry.

Lightfastness \vas compared among daylight tluorescent pain& with and without stabilisinp agents using

spcxtrophotometry and fluorescence photomctry.

Rrsults and conclusions: In tsrrns of hue. orange is the best colour for aircraft rnrtrking a s a result of a

cornpromisr: between yellow and red. O n the one hand. yellow best catches the eyes by having a hue to

[{.hich the human perceptive organ is the most ssnsitivc and by having a high reflectrince. but yellwv does

not exhibit enough contrasts apainst various backgrounds in which aircraft fly. On the other hanci. human

eyc sensitivity ro red is rather low. although red renders high contrasts agriinst various backgrounds.

Arnong various orange paints. the visibility of tluorescent orange paints is much hieher than the

International Orange paint which is a non-fluorescent standard colour for aircraft marking (in the US.

rnilitriry rit the time). Reddish orange is the most appropriate hue o f daylight fluorescent paints for aircraft

rnsrking in regard to the paint's service life: the hues of daylight fluorescent pigments shift to shorter

~savelength colours after k i n g exposed to light. thus an orange paint becornes yellowish. Addition of an

sppropriate siabilising agent impans a better lightfastness to daylighi fluorescent paints. The stabilising

agent rnay cause a slight decrease o f fluorescence but this is acceptable. Daylight tluorescent pigments are

transparent. therefore. a white undercoat is necessary to optimise the visibility o f the paint. An alkyd-type

vshiclc is generally better h a n a methacrylats-type vehicle in terms o f flexibility, rtdhesion to substratri.

pigment colour stability. and colour renderiris 3t l ave r pigment concentration. but an alkyd-type vehicle is

poorer in scratch resistance. corrosion resistance. and saturation in colour. (Co\vlingsJ.S., et al. 1959).

5.2. Cases of Conservation Treatment and Preventive Conservation Measures

This section prçsents the real esprriencc of conservators who have ~vorked o n driylight fluorescent

materials: it rnay be helpful for conservators and museum experts who have daylight tluorescent rnaterials

at hand if they can share othsr people's experirnce. Several conservators have contributcd to thih section

through personal communication upon the author's cal1 for information. This section focuses on rhe

k n o u k d g e of how to handle daylight fluorescent rnmxirils whether o r not each object contains non-

fluorescent colours. None o f the following treritment cases involves efforts to recover the overalI loss of

fluorescence that had proceeded over a pcriod of tirne.

Case 1.

Objrct: A serirs of pain t ing with daylight fluorescent paints, non-fl uorescrnt acrylic colours. and

silkscresn inks. hTot varnished.

Problerns with tluorescent rnaterials: Drirksning and decrease of saturation thrit were considersd to be

rhe result of light damage. and damage caused by poor hrindling and storage conditions-

Conservarion rreatrnents: E d s d s t n p linins. consolidation. and inpainting were perforrned as follows.

Consolidation: For f ine cracks and flakins. Lascaux .4crylic Resin P-53040TB w u applied ris 2-3 %

solution in petroleum benzine (n i th xylene as a dispersion agent), and wris heat set. For large lifting plates

of paint. Beva D-8 aqueous emulsion was applicd as 5-15 % solution in distilled water, and w u also heat

set. Funori (mucilaginous seaweed gelatine) with isopropanol had been experimented as a consolidant but

the result \vas not reponed.

Inpaintint: Including the reintegration of discoIoured retouchcs. watercolours and gouache w r e

rnainly used as inpainting materials. Dry pigments suspended in ethanol wcre applied in cracks when a

rnatte finish was required.

Exhibition illumination: Al1 light bulbs in rhc gallery are cquipped with U V fiIlers. ( I t was not

rnentioned whcther the galleries have windows and whcther the windows have UV tilters.)

Note: Current conservation decisions incorporate the assthctic concerns of the curritors in this

institution. (Ba.uter.E.J.).

Case 2 .

Object: Paintins with daylight tluorescent acrylic paints. non-fluorescent acrylic priints. and roll-ri-tex

on crinvas. Not varnished.

Problrms with fluorescenf materials: Paint losses and surface din due to an impact by a shoe.

Conservation treatment: Din was removsd with distillsd water. For the first time, the lossss were

inpriinted ~vith Magna coiours dissolved in xylrnr within tuo yertrs o f the darnage. The object was treated

rigain in eight o r ten years riftsr the first inpainting, in order to retouch the first inpaint that no longer

mcitched the colour o f the surrounding original part. For the second inpainting. a combination o f Rich Art

D-43 and Createx Orange was the best match and they wers dotted over the discoloured Magna colours.

Writercolour and gouache wçrc found IO Iravs "dead spots" \vhen applied over Magna colours-

Exhibition conditions: The painting was displaycd in front o f a taIl g l s s wall without UV filter.

Sunlight could hit the painting dcpending on the srason. (Ba.utsr.EJ.).

Case 3.

Objecr: Srveral paintings with daylight tluorescent pigments ripplied cither to a p a n o f the picture or

to the entlre picturc.

Problems with fluorescent rnatrririls: Minor paint losses.

Conservation ueatments: Inpainting with Liquitex Fluorescent Acrylic (Series 2. translucent.

lightfristness III).

Note: The conservator is awarc that the rnaterials used for inpainting will not be permanent. Also, the

conservritor is not sure how the objects will age. (Challan Bs1val.M.N.).

Crise 4.

Objrct: Painting with tluorescent pigrnc'nts and pur iche on priper.

Conservation treritrnents: The tvork wris inpriinted with Ber01 Prisrnacolor Neon Colors (coloured

pencils). The lead of the pencils \vas ground anci rnixed with rnethyl cellulose. and was ripplied on the

painting. The inripint colours mritched under driylight but thry did not have sufficient glow to match the

ori~inril parts under UV illumination.

Exhibition illumination: Rcgulrir museum envirunment. It \vas not necessary to match the tluorcscence

of the inpainting material. (Chrillan Brlval.M-N.).

Case 5.

Objsct: A set of two-piece painting with tluorescent paints and non-fluorescent paints on veneer box

and gçsso. S o t varnished.

Problems with fluorescent materials: Surface texture altercd by fingsrs, gloss by abrasion. paint lossss

criused by cleavrige. and loss on the vrneer support.

Conservation treatrnents: Surface clsrining. consolidation of drirnrigrd parts of veneer and inpainting

tvcre performed ris fbllo\vs.

Surface cleaning: Either a tvet method or a dry method wris chosen depending on the conditions of the

pain[ surfrics. The \vet rnethod \vas by swabbins with saliva follo\ved by rinsing with distilkd water. The

dry method was with Opaline pads and erasers.

Consolidation: PVA emulsion adhesive (white glue) was applied. and the parts were clamped until the

adhesi vs dried.

Inpaintins: Various combinations of fluorescent paints were applied. Thoss paints were the colour

Fluorcscznt Red (394) and the colour Fluorescent Pink (393) in the Permanent Fabric Paint Dcka brand.

and the pink paints and thé rcd paints in thé series of hobby paint. Fluorescent Demco colours. Acryloid B-

72 was used if gloss wris required. The laboratory illumination \vas fluorescent light bulbs and the windows

trwc cqujppcd \vith UV fil ter?;.

Noie: Thc colour mritchinp o f the fiuorsscent paints was s o difticult that the çonservator had to use

\vhritc\w was found to match the best. Some inpainting mciierirrls were purchased rit ri hobby shop. D t m c o

colours are not watcr soluble and cire not proven to be stable. therefore. ihcy may have to be removed

mechrinicciily and rrtouched in the future. (CC1 dossier}.

Discussion

It crin bc sriid chat the basic precautions for thc handling of driylight fluorescent materials is not s o differsnt

tlom the precriutions for the hsndling o f non-tluorcscrnt rnstsririls. T h e major difierences of the former

from the latter are the much poorer lightfastness and the hue of fluorescence visible both in daylight and

under ultrriviolrt tight. From the persprctibe of preventivs consrrvrition. great carc is necessary to protect

îvorks of art with daylisht ff uorescent pigments from light drimclge. Frorn the perspective of consenration

trcatmenr. 3 consrrvaror mriy need to specify the types o f illumination that are assthetically compatible with

thc restorrition. especirilly inpainting. and vice versa. the restorrition needs to be adjustrd to the illumination

condition in which the work will be exhibired. Inappropriate illumination may reveal the restorations thrit

rire merint to be invisible to the visitors of the exhibition.

There arc: concerns about the cornpatibility ofdaylight fluorescent colorants with various materials

Difkrent synthetic substances are usrd ris components o f driylight fluorescent colorants. and the colorants

are providrd in mriny different forms, whether as artist's priints. silkscreen inks. or solid particles for

industrial uses. If daylight fluorescent colorants are used in a \vay chat is not anticipated by the

manufricturers. no one crin predict how the pigments will change over rt long pcriod of time. Since the

mriteririls for daylight thorescent pigments are different from the materials for most other modern

colorants. the generat knowledge about modern colorants u-il1 not always apply to driylight fluorescent

pigments. When daylight fluorescent pigments are combined with other materials, the stability o f the

physical structure, as well as the chernical stability, will depend on the cornplicated relationship among the

other materials and the pigment cornponents including dyes. rtsins. and additives.

In some cases of conservation treatment on objects executed with conventional rnaterials. a perfect colour

match is avoidcd intentionally s o that the restoration is easiiy distinguished from the originaI part. The Wear

and [car that hris bcen suffcred by the object over ri long period of tirne mriy bc considcred to be a part of

the object's history or to impart an authentic apperirince to the objcct. Then. inpaintins on daylight colours

may no[ aI\vciys require a perfect colour match. In the case of a work with daylight tluorescent pigments.

howevrr. conflicfi rnay arise for r e s o n s particulsir to daylight fluorescent colours. It rnay be difficult for

some people to accept an imperfect appearance in recentIy rxccuted works o f art. T h e extrriordinririly c l a n

appearance of daylight fluorescenr colours rnay rnake damage more apparent. When the initial intention o f

the artist is not clear about the longevity of the object. a conssrvator may be challenged in decision making.

Daylight tluorescent colours are often uscd in commercial applications. and also in mriny modern art works.

but works with daylight fluorescent colours are not always intended to be long Iasting. although such kinds

o f work are added to a n collections here and there. (Baxter.E.J.) (0elval.M.C-) (El1is.M.H.. e t al. (1) 1999)

(Grinier-R.) (CC1 dossier).

There is anorher reason to think twice befors undertaking colour rnatching o f driylight tluorescent

pigments: the colour deterioration o f these pigments proceeds quickly in patterns unique to each pigment.

As a few researchers have reponsd. some daylight fluorescent pigments darken first upon exposure to light.

and then s tan to brighten while losing saturation by short period light exposure. but other daylight

fluorescent pigments d o not change their colours so quickly. An inpainted p a n that used to have a perfect

coiour match crin show a colour différence in a few years, because the colour chanse of the inpaint and the

original part proceed seprirrttelg. staning ar d i fk ren t stages of. and following different patterns of. colour

deterioration. Compared to anist grade non-tluorescent pigments that have been testcd by time. it is very

diftkult to predict how the colours of the inpainted and the original parts will change when daylight

fi uorescent pigments are used. (Baxter,E..J.) (Ellis.M.H., e t (il. (1) 1999) (CC1 dossier).

M. P. Hough. painting conscrvator. suggested to the author an idca for inpainting on faded daylight

tluorescent paints: Hough thought of using drtylight fluorescent paints that are artificially fiided to the same

degree. This idea is worth consideration. A thin layer o f the dry pigment (powder) will bc spread on a uay

and exposed to light ihrough ri transparent cover. In this case. the dry pigment needs to receive ultraviolet

l i ~ h t for ri quick fading. The extent o f the pigment's fading can be monitorcd ihrough çolorimetry or

- 123 -

spectrophotomriry, and the coIc>rimctric data or the retlcctance spectrri can be comprired betwen the

pigmcnt pmvder rind the frided priint that is \\,airing for inpainting. Now that portable colour rnccisurerncnt

devices rire rivailable, it is possible to rncasure the colour of ri paint \vithout rtirnoving ri srimple tiom the

objcxt. As portable colour instruments becorne cornmon. they wilI becorne more riccessiblc for conssrvators

becriusc colour merisurement is performrd in rnmy factories and research institutions as ~ e l l as

consc.rvcition laborritories. (Hough.M.P.) ( 1 1usbner.F.E.. rr a!. 1992) (Ling.P.P.. et al. 1996) (iL1illrkin.B.L.

19S3) (Modern Paint & Coatings S3. 1993. pp35-37) (Parkes.D. 1989) (Popson.S.J. 1997) (Snydrr.M.R.

1999). More advice is offered in Appendix III . These commrnts were contributed from a n conservators rind

from people in the colour industry.

6. Conclusion

Final Summary

It u a s rccilised that conservators d o not have good access to information o n daylight tluorescent pigments

alrhough some of them have IO \v»rk o n objects with fluorescent colours. So far. the knowledge o f daylight

tluorescent pigments gained through experience has not besn frequently exchanged among conservators,

regardless of the need t'or it- Probably this is because daylight fluorescent pigment is a new kind of artist

materkil cornparrd to oil colours and watercolours. and thsrsfore, a smrill number o f conservators have

cncountersd daylight fluorescent colours in their work- Todriy, however. day light fluorescent pigments are

used in various types of artistic and commerciril production. Art w o r k and objects decorated with daylight

fluorescent pigments have been alreridy collectcd by museums and private collectors in various

specisliscitions. and the number of collected items with daylieht fluorescent pigments will increase. Then

more conservators will have opportuniries to participate in the presrrvrition and restoration o f daylight

tluoresccnt materials. It is hopsd rhat conservators use this thssis ris an information source when they want

to know about daylighr fluorescent pigments.

Before proceeding to the conciusion, the author's position 3s a scientisr must be clarified. This study does

not investigate in the art historical aspects of daylight fluorescent colours: the significance o f this type o f

colours in the art history. the attitude of the individual arrisrs toward these colours. examples o f fluorescent

colours bsing uscd o r depicted in fine a n and Iiterature. Those fields o f study must be entrustecl to a n

historians. Neither does this research delve into the human aspects o f colour science: orgzins in human eyes,

colour blindncss and psychoIogicril. cultural, linguistic backgrounds for the concept o f colour. Although

human factors art' critical in colour perception. thcy rire out of scope o f this research. To ensure a balanced

undcrstrinding. the rcriders of this thesis a r e prompted to kerp in mind the various aspects o f daylight

tluorescent pigments ihat are yet to be investigatcd.

The CIE colorimetric systems arc' widely uscd in art consrrvrition, ripplied science and manufricturing.

Librriries contain many studies thrit utilise the CIE colorimetric systems. but how these systerns work is not

usual1y explained. The situation is similar r epd ing othc'r rypes of coIour theory. If there are conservators

ivho are looking for information on the CIE colorimetric systems or on any kind of colour theory. this

thcsis \vil1 provide them with basic information and somr ussful references.

Spectrophotometry is useful to understand colour scisntifically. although the output deviarion among

instruments and the insufficient availribility of instruments have not yet been overcome. Colonmetric data.

such as CIE L*ri*b*. \vil1 assist in specifying coIour. and retlcctance spectra obtained through

sptlcrrophotometry are effective in compriring colours. As an example of spectrophotometric data

application in art conservation. u.hen 3 tluorsscent colour is custom made for inpainting. the rnaterials'

reflectancc spectra can be compared and analysed before mixing the priints, and the resultant colour can be

prcdicted to sorne extent. Thus. the conservator can Save time and the materials that rnight be wasted in trid

and error testins.

The strongest point of this study is that tangible data is providsd. The data are new. The data were obtained

for conservation purposes rather than for industrial technology or for engineering. The rneasurements werz

taken frequently over one year. One year is not always long enough to track colour deterioration. but the

experiments in this research proceeded quickly enough to have some of the sarnples fade completely. The

graphs in the appendices provide visual rcferences of how daylight fluorescent pigments lose their colours.

The main objectives of this thcsis are to dctermine the ageing characteristics of daylight fluorescent colours

and to investigate the use of colorimetry for art conservation. The information necessary tc understand

colour deterioration and fluorescence is scattered among many domains of science and industry: physics.

chemistry, instrumenta1 rinalysis. surface coating. priint and dyc manufricturing, paper manufacturing.

riutomobilc' manufricturing and commuriication systems. Since matcrial science is important in art

- 12G -

conservation. it is necessriry to update our k n o u k d g e with information learned from the rescarch on

fluorcsccn~ materitils donc in scientitlc fields. such as mrimmalogy and engineering. thrit appear to have

norhing to du with fine a n nor hsritagc consswation. This is the \vay to gain knowlcdge. especirilly ~vhcn a

ncw issue arises. Where to find information on coIour science is prescnted in this study.

The llrht csprriment in this resrarch yielded many u d ü l results. Whrn daylight tluorescent pigments art:

e rposed to intense illumination continuously. thry lose thsir cotours much more quickly than non-

tiuorcscrnt paints do. and the hues of faded daylieht fluorescent pigments tend to be slightly more

yellowish compared to their hues when they rire fresh. Daylisht fluorescent pigments fluoresce at longer

~vrtvclcngths thm their excitation wavelengths accordhg to the Stokes law, and driyIight fluorescent

pigmenrs have their excitation wavelengths both in the ultraviolet region and in the visible rcpion. While

ultraviolet light aione can excite fluorescence in these pigments. daylight without the ultraviolet portion is

slso capable of generating intense fluorescence in these pipments. The use o f a UV filter o r a UV proof

varnish m3y be effective in reducing the fading rate of driyligfit fluorescent pigments. T h e second

csperiment visualised the approximrite contribution o f tiuorsscence rtnd rctlecrion to the colours of driplight

tluorescent pisments. This experiment also revealed thrit blue and green daylight fluorescent pigments have

lmv emission (sum o f fluorescence and reflection) cornparcd to orange and red daylight fluorescent

pigments. and thrit these biue and green dayIight tluorescent pigmenrs appear darksr than orange and red

driylight fluorescent pigments. T h e third experiment sho\ved thrit the use of a UV Iamp and

spsctrophotomeuy can help in determination o f fluorescent materials rtnd their fluorescence colours. The

results from these three experiments support the final conclusion in the following paragraph.

T o conclude this rescarch. daylisht fluorescent pigments have intense tluorescence that makes colour

matching of thcse pigments complicated: ho\vever. once the rc-tlectance spectra o f these daylight

fluorescent pigments are obtained through spectrophotometry. the colours o f thc pigments can be

undcrstood analyticrilly, as well ris visually. thersfore. conservators will be able to cornplete colour

matching of thosc daylight fluorescent pigments with lcss rrid and error by utilising spcctrophotornetry.

- 137 -

Suggestions for Later Studies

Driylight tluorescent pigments reprrsent ri ncw category in a n conservation: thereforc.. they present a

varier? of new probiems. and thsrr. rire many aspects of driylight fluorescent pigments that need to bc

studied by rirr conservators rind conservation scientists. The fotlowing is a list of sufgestions for tater

studics that will lerid to a better understanding of drtylight tluorescent pigments.

-- Examining complete excitation-emission spectra of driylight fluorescent pigments using two

monochromators in ri spectrophotorneter to scan the excitation radiation and the emission f ron the

pigments at the same time. The study of Wrillen provides an r?crimple of this technique (Wa1lert.A. 1986).

-- Study of driylisht fluorescent dyes' tluorrscence and chernical characteristics through molecular

rinrilysis.

-- Various tests to compare the chemical and physical stability of daylight tluorescent pigments and non-

tluor~scsnt pigments. for example. tsnsile testing of paint films, merisurement of e l a s cransirion points.

chernical tests. solvent tests. rind so on.

-- Cornparison of dayiight fluorescent colours on crinvas. on paper. and o n textiles. in terms of their aging

processes rind the most appropriate conservation rnethods.

-- Finding effective rnethods and stntegies to reduce UV esposure for difkrenc types of daylight

tluorescent rnaterials. such as commercial posters, book covers. priintings without varnish. art work

exhibitcd under black light. textiles in low-budget exhibitions. and masterpieces in private collections.

-- Cornparison o f various inpainting techniques for daylipht tluorescent pigments. Some techniques are

introduced to the reader in the section "Case Studics and Conservation Suggestions."

-- Survey of driylight tluorescent colorants on the market availrtble now and in the past. and of the

rnrinufacturers of these products.

-- Survey of artists who have used daytight tluorescent colours, of their work, and of a n collections that

contain driylight fluorescent work.

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Arcblette's Hmidbook of Pliorograpliy atid Rqrogrnpiiy: rnaterials. processes and systems 7Lh ed. 1977. Van Nostrand ReinhoId Company: New York. NY. USA. pp.551-555.

Varnishes. paints and othcr painting compositions. A4utcriclls und Tecli~iology ( 5 ) . 1972. Longman Group Ltd./ J.H. de Bussy: Amsterdam. Netherland. pp.3 17-320.

Park service uses color technology in restoration projects. Modeni Païttt & Conritigs S3. M a y 1993. pp.35- 37.

DAY-GLOIAdditives 199 1. Plasrics Etigitieerhg Seprcrrrber 199 1 . p. 19.

~Wirritigroti's Dicriotian of Plasrics. 1993. Tecnomic Publishing Company, Inc.: Lancaster. PA, USA.

Jrzridards and Product Literature

AATCC Tcst Method 16- 1990, Colorfastness to light. AA TCC Tecirtiical Mattual 1992. 199 1. American Association of Textile Chcmists and Colorists: Research Triangle Park, NC, USA.

AATCC Tesi Method 139- 1989. Colorfastness to light: dstection of photochrornism. AATCC Techicd Matiarrl 1992. 199 1. American Association of Textile Chemists and Colorists: Research Triangle Park. NC, USA.

Standard sptxification for anists' oil, resin-Oil. and alkyd pain&. D-1302-90- 1992 Ariniral Book ofASïXf S ~ c i ~ i h d ' i v.6. American Sociciv for Testing and Materials: Philadelphia. PA. USA.

Standard test methods for lightt'ristness of pigments used in rirtists' paints, D4303-91. 1992 Aruirrd Book of ASTA1 Slcr~tdczrtls v.6. American Societv for Tesiin9 and hlaterials: Philadelphiri, PA, USA.

Standard practice for obtaining spectrophotometric data for objcct-color evaIuation. E 1 1W-9 1. 1993 Anniceil Book of ASTM Srnrrrfards v. 14. American Societv for Tesrin2 and Maierials: Phiiadelphia. PA. US.4.

Standard Test Mrthod for color and color-difference mrasurement by tristimulus (tiltsr) colorimetry. E 1347-90. 1992 Arirircal Book of ASTM Srciridards v . I-l. Arnerican Societv for Testinc and Materials: Philadelphia. PA, USA.

Standard test method for transmittance and color by speçtrophotornetry using hemisphericrtl geornetry. E 13-48-90. 1992 Atmml Book of ASTM Sraticlartis v . 14. Arnerican Society for Testinz and Materirils: Philadclphia. PA. USA.

Standard practicc for conducting sxposures IO dayligh! fïltsred through glass. G24-S7. 1992 Atinlral Book of ASTM Simickrrcis v.7. American Socie~v for Tescino and Marerials: Philadelphia. PA. USA.

Standard prrictice for operrtting light-exposure apparatus (xsnon-arc type) with and without water for exposure of nonmetaliic materials. G26-90. 1992 Anrtical Book ofASTM Smndards v.6. American Societv for Testino and Materials: Philadelphia. PA. USA.

Tlie 3000 BYK-Garrlrier Irtsrrrcrwrirs Carcrlog. 1999. pp 1 1-1s. BYK-Gardner: Columbia. MD. USA.

rtlicro-TRI-gloss. Mirror-TRI-Gloss. Operuri~i~ lris~r~tcriorrs- BYK-Gardner Inc.: Silver Sprins. MD. USA.

Specrrogard I I Color Sysrem Operaior's kfaiiual. prelirninary, software version # 1.2. 1990. B YK-Gardner, Inc.: Silvcr Spring. MD. USA. -

Dai-Glo. Dav-Glo CoIor Com: Cleveland. OH. USA. hrtp://\vww.dayglo.com/

Golden Fluorescent Acrylics. (Fluorescent paint sample chart.) Golden Anist Colors. Inc.: USA.

Fabri-Tech Day Glow Vest. Grand Prix Eauestrian Products: Woodinville, WA. USA. http://gprix.com/ftv.htm

Day-Glo Ink Alen- hlallov Litho~raphinp, - Inc. 1997. hrtp://www.mallov.com/malartiy/articledda~~~o

O-Lab Wratherino Rcsearch Service, Miami, FL. USA. (Pamphlets): Know your enemy: Clirnatc data cnhances interpretation of weathering results (LL-9035). 1997. WiIl your product last outdoors? (LL-9000.2). 1996. Q-SUN Naturai sunlight concentrator. super fast results from natural sunlighi (LL-9052).

Thc O-Panel Cornpanv, Cleveland. OH, USA. (Pamphlets): QUV accelerated wcathering tester: A choice of Irirnps for the QUV (Bullcriri U-8160). 1993. Controllcd irradiation in Iaboratory weathering: Limitations in the state of the an (Tecliriical Bulleri11

L-SOIO). Correlation Questions and Answers (L-833- l/S4). Q-U-V acçeleraicd weathering icstcr: A choice of Iamps for the Q-U-V (Btclletitz L-8 16).

O-Pancl Lab Products, Cleveland. OH, USA. (Pamphlets): Lab Notes. Sumrncr 1996. LU-SO I i -2 (REV.1/96) Tcst methods and material standards specifying the QUV. partial list (LU-Sol2 ( 1/95)). Improved UV light source snhances correlation in accrlsrited weathering (Bulleriri LU-6003).

Originrilly published in Plasrics Cotripoit~iciiti~. MarchfApril. 1987. Know your cnemy: The wrather and how to reproducs it in the Iriboratory (Tecl~tiicul Bitlfe.ritz LU-

OS2 1 ). l99-l.

Brightncss of pulp. paper. and paperboard (directional rrllrstance at 457 nm). T 452 om-87. 1967. TAPPI Technical Committee.

Tri-Art Finest Quality Anist Acrylic Colours. (Product list) Tri-Art Manufacturino Incnmorated: Kingston. Canada.

Tri-Art Finest Quality Artist Acrylic Colours. (Colour chan) 1998. Tri-Art Manufacturino - fncorporated: Kingston. Canada.

Cczy OS/2 systerri, Versioti 2.00. Sojhwre operatioii rrinriitni. Publication No.85-101249-00. January 1996. Varian Australia Ptv Ltd.: Victoria. Australia.

UV-Vis Specrrophotometer System. Cary i niid C a v 3 Smice Mariual. Publication No.S5- 100773-00 ( 1). June 19S9. Stewart.M.P./Varian Australia Ptv Ltd.: Victoria. Australia.

VASARI: Visual arts systrrn for archiving and retrieval of images. h ttp://azul.ecs.sotonhttp://rizul.ecs.soton.ac.uk/-km/projs/vacC~k/-km/projs/v

Toxicolooy Reports. Vert~totir Safce frifoririurioti Resourccs. /tic. (Verrrtonf SIRI) MSDS hide-r. h ttp://hazard.com/msds/

Day-glo Fluorescent Orange-red Pigment # 1062. Day-glo Fluorescent Oranse-red Pisment # 1062. 4-Arninonaphthalic acid phenylimide (4-amino-N-phenyl-Naphthalimide) Rhodamine S Rhodamine B Rhodamine 6GDN (Rhodamine ZH)

Informal Sources of Information on Conservation Trcatment and Prevcntivc Conservation of Daylight Fluorescent Materials

CC1 dossier No 1000-476. Canadian Conservation institute: Ottawa. Canada.

Psrsonal Communication: Baxter.E.JJ Carnegie Museum of Art & The Andy Warhol Museum: USA. Berthe1.B J Golden Artist Colors, Inc.: New Berlin, NY. USA- Bogstadt.CJ Tri-Art Manufacturing Incorporated: Kingston, Canada. Challan Beival.M.N.1 Musée d'art contemporain d e Montréal: Montreal. Canada. Ellis.M.HJ New York University: New York. NY. USA. Gagnier.RJ National Gallery of Canada: Ottawa, Canada. Goldmann,MJ Ncw York University: New York, NY. USA. Graphic Resources: Canada.

t1rirrin.D.D.l Canadian Conservation Institute: Ottawa. Canada. Hqes.J./ Golden Artist Colors, Inc.: New Berlin. NY. USA. Hou_rh.M.PJ Queen's University: Kingston. Canada. h1arrhews.S J GoIden Artist Colors. Inc.: New Berlin. NY. USA. Vancs.EJ FoIio Kitchener: Kitchener. Canada.

APPENDICES

APPENDIX 1.

Applications of Fluorescent Colours in Science and Tec hnology

In the field of science and tschnology. colorants rire not riluriys identified whethsr they arc daylight

tluorrscent or UV fluorescent. Fluorescent pizments and dyes rire often used ris tools for scientific studies

and as materials for equipment in engineering and in high technology. The studies introduced here show

how speciilc types of daylight fluorescent pigment are chosen for specifrc purposss: these pigments are

chosen for their emission intensity that is suprrior to phosphorescent pigments. they rire chosen for their

tluorescencr hues. and they are chosen for their tluoresccnce thrit is erisiiy detected under ultraviolet iisht.

The follo\sing studies rilso show the examples of methods to detzct, distinguish and quantify driylight

tluorcscent pi, ornents.

Radar Display

Yrtmada expects radar display to fxcome one of the applications for dayiight pigments. Plan position

indicator scope (PPI scope) is the most widely used type of radar display system. This system utilises a

cathode-ray tube (CRT) with phosphorescent pigments ' because the systcm requires 3-5 seconds to scan

one frarne of image. Due to the low brightness of the pigments. ri PPI scope needs a hood to shut out the

nmbient light, and there Eire technical difficulties in rnanufacturing large CRT monitors. therefore. CRT is

not appropriate for a large s i x display that is viewcd by many people in a meeting. In order to overcome

the problems with CRT display and to deveIop a large s i x radar display. Yarnridrt explored the possibility

of driylight fluorescent scrcen combincd with Iriser excitation. In the crise of a CRT type radar display.

clectron berirn excites P7-B. a phosphorescent pigment thrit emits blue light only for ri short period of time.

' Phosphorescent pigments maintain the former image until the next image is projecicd on the display.

- 139 -

and thc blue light of P7-B excites P7-Y. rinothrr phosphrmscent pigment that emits ycliow light for a

luiigrr prriod of tÏmc. P7-Y c'an be e~ci ted b~ laser beani direstly ' liir ti iaser type display. howrvrr. the

Iriser bcrirn crerites tlickcring spcckles on thr' display and mrtkcs the observer's eye sorr. In contrast to P7-

Y. an orange daylight fluorescent pigment and a yellow drtyIight fluorescent pigments were found to be

much brighter when they were excited by argon (Ar) laser at I S S nrn (blue). No disturbing speckles were

obscrvrid tvith excited orange daylight tluorrscrnt pigments besause these pigments absorb Argon laser

\ceII. The emission frorn a driylight tluorescenr pigment di>c.s not trist during a scanning inrerval. but the

3 image c m be mriintained by storing a framr of image in the computer rnemory. Yamada reponrd that the

orange daylight fluorescent screen was comfortable for viewing. The daylight fluorescent pigments used in

this study \vere also used for office supplies and there were about eight colours ranging from green to red.

( Yrimridri.H. 198s).

Cockpit Instrument hlarking

L'cve found that in a helicopter cockpit. the night vision gogglt-s for the pilot \vert= most cornpaiible with

indirect UV I i~ht ing associared with instrument markings of a yrltow-green fluorrscrnt paint with A, '

riround 550 nm. Fluorescent paints were choscn &cause rhey wrre visible under UV illumination. The

night vision system h z been used to support helicoptt-r pilots \vho undenake night rnilitary missions. The

night vision system projects the exterior view on the interior of the helmet or the interior o f the go_ogles that

are worn by the pilot. In order to prevent the cockpit illumination from interfering with the image projccted

on the goggles. the illumination spectrum and the emission spectrum of the fluorescent markings on

instruments must be outside of the go&s' response spectrum, 600-900 nm. The dispiays on the

instruments must be seen well with mesopic vision because helicopter pilots see the night vision display

The reason for using the differeni excitation proccss between CRT type display and Iriser type display is not explaincd in Yamada's article.

Probnbly by continuously exciting the screen with the stationary image unril the ncxt frarne is projected. ' I t is not cited whether this wrivelength is the maximum fluorcsccnce emission wavelength o r the \vavelen~th with the maximum reflectrince that is the sum of fluorescence and reflcction.

ui th mesopic vision. Mesopic vision is an intermediatc statr between photopic vision and scotopic vision.

Photoplc vision rs a stritc of human vision adaptrd to daylight with the maximum sensitivity at 556 nrn

!yélIci~v-grt.cn). and scotopic vision is adapted to a dark surrounding ~v i th the maximum sensitivity rit 507

nm ( blue-zrczn). (Veve.M.A. 1985).

Daylight fluorescent pigments are often uscd as traccrs. The Rocket Red pigment (AX series), provided by

D q - G l o Colour Corp. (Cleveland, OH. USA). wris used by Newman. e t al. to develop a new technique to

trace solid particles in natural water systerns. In the theory o f Newman, e t al., fluorescent pigment particles

crin bc suspended in s e w g e IO represent panicies that settle and coagulate in natural water. Fhorometn

\vas combined withflotr? cyronirtc to mecisure rhe numbrr concentration and size distribution o f panicies,

on the assumption that fluorescence intensity \vas proportional to the surface area o f the pigments.

Sc-ci mit^^ rlrcrrolt rriicroscopy ( S E M ) utas also used for the sarne purposes. T h e advantages o f the

fluorescent pigment panicles were the ease of drtcction ~vith well-dsfïned specific gravity, panicle size and

coagulation chriracteristics. The Rocket Red pigment wris escited at 436 nm and the peak of its

tluorescence (E-,) \vas 600 nm. The pigment usrd in this study wris ri solid solution o f a fluorescent dye in

ri sulfonamidr-tririzine-aldehyde thermoplastic resin matrix. (Newman.K.A.. e t al. 1990).

In another study, Day-Glo's Rocket Red was used to quantify the amount o f pesticide that wris captured on

iht3 surfxe o f the aerial spray target In this study. the fluorescent dye Rocket Red T-13, provided by A. R.

Montcith Ltd.. ' was mixed in a solution that simulated a pesticide liquid. and the solution was sprayed

(rom an aircraft. The dye wrts extracted from the collecting surfaces with organic solvent and was subjected

to UV absorption mmeasurement with a specrropkorotneter. Shimadzu UVl6OU (Shimadzu Scientific

5 Day-Glo Corp.'s distributor in Canada. fi iVallert (Wri1lert.A. 1986) and Newman. e t al. (Newman.K.A.. et al. 1990) measured fluorescence (cmission). however, Sundaram, et al. (Sundararn-A.. e t al. 1992) measured absorption in this study.

Instrurncnts. Inc.. Columbia. MD. USA). The UV absorption of each srimple was rnrasured rit the dye's

maximum ribsorpion wavelcngth ( A , = 231 nm) to determine the dye concentration in the sarnple

solution that corresponds to the arnount of the deposir on the risrid spray target. (Sundararn-A.. et (il. 1992).

"V, two Fluorescent pigments arc effective u-ricers for small nocturnril animals. In the Journal of Mammrilo,_

groups reportrd the use of tluorescent pigments for tracking the activities of wild rodents in the natural

cnvironrnents. Those fluorescent pigments wrre obtriinrd from Radiant Color (Richmond, CA, USA) . In

one repon, Lemen, et al. uapped an imls after sunset, shook each animal and fluorescent pigment powder

in ri plastic bag. then released the animal. The pigments were left on vegetation that the animal contacted.

In anothcr repon. Longland et al. marked Indian ricegrass seeds by shaking 40g of seeds (ca. 1 1.000 seeds)

\rith 3.0g of tluorescent pigment powder in a plastic bas. The seeds rnarked in different colours uxre

plriced in nritural sites. wild rodenrs coilccted the marked seeds. and the pigments \vere transferred to rhe

animal fur. Once the seeds were buried in the cache sites. the pig-nents ~vere transfrrred CO the soi1 from the

animal fur and from the seeds. In both studies. the animal [rails were rnarked u'ith tluorescent pigments and

\r.ere trackcd under long-wave UV Iamp. during the night following the mrirkinz. Longland. et al. found

that their search \vas more efficient when moonlight was absent. ontl land, et al. used green. oranse and

rzd tluorescsnt pigments for thcir study. Prior to the study of Longland. et al.. Lemen reported thrit = oreen.

orange and red were the most easily de~ected and disringuished among sevsral colours. Mixing of pigments

could increasc the variety of markcrs to 17 colours or more. The colours gained by mixing pigments were

difticult to distinguish from each other in the field. but 1OOx rnagnification enabled the rescarcher to

idcntify the colours of those mixed pigments. (Lemen.C.A.. et al. 1985) (Long1and.W.S.. et al. 1995).

7 This term is assumcd to be ultraviolet fight with long waveiengths that rire close to the visible rangs. For cornparison. near-UV ranges from 320 nm to 4OOnm (Veve.M.A. 1985) o r frorn 200 nm to 3ûûnm (McDowelLR-S. 1997). S Probably this was bccause nothing but fluorescent pigments were visible under ultraviolet light when it upas very drirk. but many other things were also visible under moonIight. thus rnaking it difficult to dist inguish the fluorescent pigments from the backgrounds. 9 The resultant colour with intermediate hue is less saturatcd. or weaker. thrin the colours of the original pigments because of the broadened colour spectrum. (Gerritsen,F. 1983. pp. 152- 153) (Str3in.R.A. 1976) (By1cr.W.H. Pigrrzertt Handbook v. 1. 1973) (Voedisch,R.W. Pigment Handbook v. 2- 1973).

Thc information from the manufacturer convinced Lemen. et al. (Lernen.C.A., ct al. 1985) and Longland. ct

al.. (Lon~Jcind,W.S.. et al. 1995) thai the pigments were safe for rinimals. Lemen. et al. observed no acutc

tosicity of the pigments on rininirils. however. none of thc two studies mentions the long-term toxiciry of

those pigments. And this. by no rncans. irnplics the pigments' safety to hurnan health whether by skin

contact. inhalation or ingestion. A s for the satetu of UV larnps. UV-proof goggles mriy be necessriry . Both

studirs cite the relative safsry of Ionz-wave UV but none of [hem mentions the protrctivç masures thrit

they had taken for their tieldwork. .4s Moffeir. et al. reported. tluorcscent pigmcnts are also used to idenrify

the travelling route of fish for fishery study. (Moffett.1.J.J.. et al. 1997)-

APPENDIX II.

Natural Colour System

Arnong rht: cdour systems listed in the section "History of Ccilour Theory," those of Johansson. Hesselgren

and Hird rire in the category of r i r r f ~ i r c d coloirr s j s ~ t . l ~ (NCS). (Ag0ston.G.A. 1987. pp-133-13).

(Gerritscn.F. 1983. p-19). The concept of the natural colour system may have originated with the German

physiologist Ewald Hering (1834-19 18). Much theoretical and rxperimental research on colour perception

has been d a d o p e d from Hering's theory about colour vision. The NCS colour solid is a double cone that

is sirnilx to Ostwdd color ~ o l i d . ' ~ (A2r)ston.G.A. 19S7. pp. 133-1 38). (Figures 10- 1s).

As Asoston strites, ' T h e Swedish Narural Colortr S~stenl (NCS) provides an effective means for everyone

s*ith normal color vision to m a k color evriluritions \vithout the use of color-merisuring instruments or of

color srimplzs for cornparison. The nritural colour system crin be ernployed dirsctly for determinin2 the

perceived color o f a wall in a room. of a folirigr in the distance. of a paintsd area in which simultaneous

contrast occurs. of a spot on a television screen, etc." (Agoston.G.A. 19S7. p. 133). A colour deterrnined

\cith ri narurd colour systern is resarded as an absolute rncrisure based on hurnrin colour perception.

Psychophysical colour determination. thrit relies on colour matching. is often diffèrent from the colour

determination through the natural colour systsm. People crin distinguish among 10 million colour stimuli

under favourable conditions, but "our ability to identify a color with sorne certainty is a great deal less," as

Agoston qucites from H h d . (Agost0n.G.A. 1987. p.133). The total nurnber of colours is probably about

10.000 or 20.000. A. Hird and L. Sivik claim that this level of perception crin be met in the natural colour

systern. (Ag0ston.G-A. 1987. p. 133- 138).

10 Thcse colour solids are also called ciilour spaces (Agoston.G.A. 1987) o r three dimensional colour diagrams. (Gcrrrtscn.F. 1983).

The naturd colour system is explriincd in detail by Agoston (Agoston.G.A. 1987. pp. 133-138). "Basic to

thc YCS is the recognition of the six ps~clrologic-cd primczrics: white (W). black {S. !Or the Swedish word

' s ~ a r t ' ) . ycllow (Y). rcd (R). blue (BI. and grecn (G). Thc hst four are the unitary hues " : the yelluw that

is neithcr grccnish nor reddish. thc red that is neither yello\vish nor bluish. the blue thrit is ncithrr reddish

nor grecnish. and the green that is neithsr bluish nor yellon~ish. AI1 other hues are recognized as mixtures of

t ~ v o unitrin hues; for sxample. grwnish ycllo\vs. reddish ycllows. yellowish reds. bluish reds."

(Xgoston.G.A. 1987. p. 133).

Colour j u d p n r n t by the natural colour system entails a few steps. First. the hue must be detemined

according to the Hering hue circle. The Hering hue circle consists of four unitary hues, ycllow (Y). red (R),

blue (B). and green (G). as well as hues in binriry compositions. which faIl between the unitary hues.

presented schernaticrilly rilong the circle. (Ag0sron.G.A. 19S7. pp. 133-1 38).

The NCS hue circls may help in undrrstandinp the natural colour systern. It shows the hue scale (must be

rtxd clock\vise) in NCS notation. The basic structure o f the NCS circle is triken from rht: Hering hue circle.

In both circulrir diagrarns. al1 positions in each quadrant of the hue circle are occupied by binary mixtures

of unittir? colours in which the hue of cach mixture changes gradually and continuously from one unitary

hue to rinother. Bet~veen Y and R. for example. rhe hue gradually changes starting from yellow. to reddish

yellotv. through an rqual mixture of yellow and red. tu yello\vish red. and the hue finally reaches red. At

the midwiy position in the Y/R quadrant. the binary hue (indicated by the dashed line of radial) is given by

1 1 Thesc colours cannot be describcd using other colour names whercris purple can be described either as reddish blue or ris bluish red. For example, a red can be a purplish rcd o r a rcd with an orange shadc. but these expressions contain the word red. Although green can be produced by mixing yellow and blue pizments. grcen is rccognised as one colour rather than an intermediate cotour between yellow and blue. There arc greenish yellow and greenish blue. but the word green cannot be replaccd by the expressions "yellowish bfuc" and "bluish yellow." In one theory. the human eye is no& able to recognise a colour in such w y s as whether it is yellowish blue or bluish yellow. and whether it is reddish green o r greenish red. Human eye hris a colour scnsor for each of the thrce additive primaries, blue, grcen and red. (Agoston.G.A. 19S7f (Levkowitz,H. 1997). The bluc. the grcen and the red to which the hurnan eye is sensitive are called the q e prirtiuries. (Gerritsen.F. 1983. P68).

the notation Y50R. reprcsenting ri 50150 mixture o f the unitriry ycllow and the unitriry red. Similarly. b-OB.

B5OG. and G50Y represent 50150 mixtures bstween two of the unitriry yellow. the unitary red. the unitriry

b lus and the unitary green. (Agosran.G.A. 19S7. pp. 133- 13s).

For hue judgement. a n observer identifies the t\vo unitary hues a s components o f the hue being judgrd.

thus. the hue of the spccimen is losated in the quadrant o f the hue circle. Next. the observer judges the

relative proportions o f the two unitwy hues rrquired t o produce the spec imen hue. An example of hue

judgernent is cited by Agoston (Agoston.G.A. 1987. pp. 134- 135). "The observer miiy decide that the hue is

a binary mixture of blue and green. requiring location in the B/G quadrant o f the Hering circle. Imagine

that. sf ter some consideration, the hue is judged to be 70 7c unicary green a n d 30 % unitary blue. This

bluish green hue is located in the BIG quadrant. 7 0 9 of the way a l o n r the a r c (reading clockwise) frorn B

to G. T h e NCS notation for this hue is B70G. tvhich means 7 0 % unitary g r een and the rrst unitary blue.

( T h e 30 % for unitary blue is not t r~ i t ten , becriuse it is easily obtained by subtract ing the percentags for

unitriry green from 100)" (Ag0ston.G.X. 1987. pp. 133- 13s).

The second major step is the determinrition o f the ratio o f black. white and hue in the colour. T h e terms.

A'CS blacktess. rVCS whireriess and A'CS citrorrinricrless rire applied t o the relative amounts o f white (IV).

black (S). and the chromatic component (C) which repressnrs the hue. respectively. To continue the colour

judgement for the bIuish green lvith the hue BÏOG, suppose that the observer's decision o n the relative

amounts a n S = 20 5%. W = 30 52 and C = 50 %. This set of numbers is al1 that is ncedcd for the NCS

colour specification. in this case. 2050-B70G. As ri matter of convention, t he relative amount o f black S (20

Ci; ) is listed first. then the chromatic componenr C (50 %). and finally the hue 's specification (B70G). The

colour is specifisd only with two of the thr re components. the relative amounts o f black (S) and hue (C).

but the amount o f white (W) is omitted. There is no need to statc the relative amaunt o f the third (W). It crin

b<: obtaincd sirnply by subtracting the sum o f S and C from 100 bccause the total o f S. W and C is always

100 56. (Ag0ston.G.A. 1987. pp. 133- 138)-

The n~iturril colour systern is useful. a s Agoston quotrs from Hird. "At thc Scandinavian Colour Institute.

extensive tests of the application of thc NCS have shown ihrit pcoplc with no panicular knowledge ribout

color and ni th no previous experirnce o f color specification o r color mcasuremrnt arc capable of making

judgt.nicnts of' hue and relative quantitics C, Ur. and S unrtided by color sarnples." (.-\goston.G.A. 19S7.

p. 136).

The Sicedish Standards Institution (SIS) hris adoptsd the NCS ris a S~vcdish standard for cotour notation

and ri colour atlas (SIS Colour .Atlas NCS. Swedish standard No.019102) as a practicd illustration o f the

system. The Atlas displaps I3 12 rnatt color chips (1.5 x 1.3 cm) and is useful for the precise specitication

o f colours on the bnsis of perceptual criteriri. The application of the Atlas. as \vcll as the Book of Color, is

restricted to specitic conditions of illumination and background (white. NCS; middle gray, MunselI). The

Atlas and the Munsell Book o f Color rire usod in similar ways. but the Atlas is not required for NCS colour

judgemsnts (Ag0ston.G.A. 1987. pp. 133- 138). Agoston ernphasises that the NCS is "a system for denoting

colors as and Lvhen rhey apperir to man" (Agoston,G.A. 19S7. p. 137).

APPENDIX III.

Suggestions for Handling of Day ligh t Fluorescent Materials

This section prcsents practical information and suggestions thrit may help conservators in handlins daylight

fluorescent materiaIs, Academic reports. conservators' advicr and manufacturers' information on daylight

fluorescent pigments have been obtained both through publications and through persona1 communication.

Stability of Dûylight Fluorescent Pigments

One manufacturer sells fluorescent paints only in a student grride but not in an mist grade brcause of the

poor lighrfastness o f daylight fluorescent pigments that does not mert the company's snist grade criteria

(Bo2stridt.C.). Another manufacturer warns that tluorescrnt pigments should not be expected to have

archiva1 grade quality nor li~htfastness (Benhe1.B.).

Thc colours of "daylight tluoracent pigments last alrnost indefinitely indoors but graduaily fade

outdoors."" For severe outdoor expusure, a high pizmcnt loading ( 1-2 prins pigment per i part of vehicle

solids) on the fiuoresccnt coating is necessary and the final dry fillm thickness must be 2-3 mils. To

maximise the pigments' Iife, UV absorber can be mixed in the paint vehicle, and an additional topcoat with

UV absorber works even better. Additives such as substituted benzophenones o r benzotriazoles can

'' Several military standards had specitiled the methods for application of daylight fluorescent pigments: The thickness of a fluorescent paint film is 3 mils ( 1 mil = 1 x IO-^ in = 0.025 mm. 1 mm = 40 mils) after it dries. and a clear overcoar containing UV absorber is applied over the paint layer in 1 mil of thickness. A, coating Iaycr that satisfies this spccificrition must withstand 120,000 Lngley units ( 1 h n g l e y = 1 caikm' = 4.184 Ucrn'. cal: calorie. J: Joule) of exposure. that equals an ouidoor exposure for about 8.5 months in Florida. U.S.A.. with the minimum of 160 9 reflcctance at the dominant peak and with the maximum shift of thc dominant wavelength by IO nm (Vocdisch.R.W. Pigmerlr Haridbook v 2. 1973).

incrcasc ihc lightfastness o f driylight fluorescent pigments b!. 50 % (Voedisch.R.W. Pigrrrenr Fialidbook v

2 . 1973).

Conhtanr hcating degrades daylight tluorcscrnt pifrnents scvsrely ( Voedisch.R. W. Pigtnerir Hantibook v 2.

1973). '.Mritrix of the pigment I3 is soluble in (or affectrd by) solvents such as low rnolecular weight

ketones and esters." (Voedisch.R.W. Pi~nierlr Handbook Y. 7 . 1973. p. 145).

Compatibiiity of Daylight Fluorescent Inks

blalloy Lithographing Inc.. book manufacturer. has reponsd an incompatibility between some of Day-Glo

printing inks and Malloy's UV coating system." If the UV coating is applied over the Day-Glo printing

inks. the UV coating exhibits çhipping and tlaking " becauss of wax contained in the inks. As an

alternative to coatins. film laminrition is available although the latter is more expensive (Malloy. 1997).

Adjustrncnt of Fluorcscencc and Huc

A small amount of titanium white can be added in ordcr t o reducri the glow in daylighr and under ultraviolet

Iight (Berthe1.B.).

Non-fluorescent toner '' with a similar hue rnay be added to a daylight fluorescent colorant. Toners rapidly

decrerisc the brightness o f the colour, and 1-10 % of toner against the arnount of the fluorescent pi= ornent

wiII be satisfactory (Smith.T. 1982).

13 Not the matrix of thc medium. 14 A coriting that cuts off ultraviolet light. 1s Irnplics a poor adhesion between the ink Iayers and the coating. 16 A "full strength pigment" that is not cxtended (mixed) with other marerials (Colour Index 3rd cd. 1982. p-6).

A bright pastel çolour is produccd by adding an opaque white to a fluorescent colorant. Adjustment of

brightness is possible by adding ri non-fluorcscent colorrint to ri fluorescent one. thus obtaining ri semi-

f l u o r t x c n ~ colour. To create a hue of fluorcscsnt colorant that is not manufacturai. mix two fluorescent

colorants to obtriin an intrrrnsdiars hue (Desi.qnirzg trSirli Dtr~-Glo Color. 1998. p.28). The I a s t technique

may, houever. result in a drcreased saturation or a decreased colour strength (Agoston,G.A. 19S7. pp.4 1-

44) (By1er.W.H. Pisnzenr Hmci6ooX- v. 1. 1973) ((3erritsen.F. 1983. pp. 152- 153) (Voedisch,R.W. Piprerir

ilarid6ook v.2. 1973). although the mixture mriy exhibit an intcnsified fluorescence and an enhrinced

saturation in sorne cases (Streite1.S.G. 1995. p.599).

Inpainting and Colour Matching

Colour rnatching of daylight fluorescent paints that have rilready strined to fade duc to exposure to lisht crin

be treated as colour rnatching for any colour (Berthe1.B.).

Treatment of Dimensional Damge on Paint Layer

For the irearment of cracking and firiking. it wouid be necessary to know the specifics of the paint system

used for the work. Knowing the binder system of the paint film is critical in restorrition. Generally. the

practices to treat cracking or flaking in other types of painr can be applied to tluorescrnt pain& (Benhe1.B.).

Illumination for Conservation Treatments

Whzn daylight fluorescent pigments are mixed with non-fluorescent pigments. colour rnatching is casier

under black light " than in naturd light because the colour of a daylight fluorescent pigment can be very

diffcrent from the colour of the glow under black light. It would be rilways wise to test the colour match

17 This comment rnay be rncant for paintings to be rippreciated under blrick light.

under riIl light sources cxpectcd. ris the tluorcscent inpaint \v111 dcmonstratc drastically different results

depcnding on the type of illumination (Benhe1.B.).

I l lumination for Exhibition

A painting that \vas intended for viziving under black light \\.ris exhibited with black lighi illumination

(Brixtsr.E.J.).

Works of art with daylight fluorescent pigments are best vieived under ultraviolet light cxclusiveIy or under

full spectrum visible light. but then riccelerated light drimape on the pigment is inevitable: therefore. a

compromise betwren riesthetics and preservation is often recommended (Ellis.M.tI.. et al. ( 1 ) 1999).

Effort must be made to minimise the esposurs of the piecc of \vork to ultravioIet light and short \vaveIength

light. Use of rirncrs activated cither by vic\r.ers or motion sensors \vil1 extrnd the period of time before

darksning oocçurs in the pigments. Undrr ri regulrir and intermittent level of illumination, a signitïcant

darkening mriy occur in less than tive years (Ellis.M.H.. et al. ( 1) 1999). There are some examples of

ultraviolet iight illumination t'or exhibition in the litsrature f3agot.D.. et al. 1972) (Douvncy.L. 1998)

( Luxncr..A. 1998).

UltravioIet Light Filtration

.+y UV absorbing or UV reflectins varnish will dramatically rsduce the fading of daylight tluorescent

pigments but will not do so enrirsly (Berthe1.B.).

.At least thrce Iayrrs of UV proof vanish is necessriry. and the evenncss o f varnish coating is essentiril to an

evcn fading. therclbre. spray is often the best mcthod for applicstion o f UV proof vrirnish (Berthe1.B.).

Artistx are informed by the paint manufricturr.r thst driylight tluoresccnt colours are not lightfast and that

thosr: pritnts should be p n m c t e d wirh ri U V filtering varnish ( i-fayrsJ.).

Therr: ivas ri painting merint for exhibitions under blrick light. and protection againsr ultraviolet lisht was

impowble in this case (Bsxter.E.3.).

Alkyd-type paint medium absorbs ultraviolrc light mors than ticrylic-type medium does, therehre. in

throry. the p i ~ m e n t s wilI be protected from lisht damage more in rilkyd-type medium than in acryIic-type

medium; however. alkyd-type materiaIs tend to becorne yrllowish upon aging more sevcrely than acrylic-

typc rnriterials do. If a clerir paint medium pi& up a yellotvish hue, it \vil1 adversely affect the appearance

of the priint. thus. tht: ridvantage o f supsrior L'V absorption \vith alkyd-type medium is cancelled by the

colour detrrioration of the medium itself (Boptadt.C.).

It'a driylight fluorescsnt paint is covered \vith a clecir. UV absorbing topcoat. its outdoor lightfastness will

be improvsd significantly. T h e paint uill rippsrir slightly darker because the coating rrduces the total

rimount uf ultrlivioiet light chat rerichcs thc priint; the coating grcritly eliminates the short wavelength

ultraviolet light that is more hazardous to paints. but it transmits a sufticient rimount of ultraviolet light at

thc lonsrr nuvelengths to excite fluorescent<: ( E l l i ~ , ~ l . H . . et 31. ( 1 ) 1999).

Additives such as hindered amine light srabiliscrs (HALS) rire used to retard decomposition of daylight

fluorescsnt pigments (Ellis,lM.H., et al. ( 1) 1999).

:\ dririi riiom storage will reduce fading of tluorssccnt materirils. but an work with daylight fluorescent

pigments are oftr'n treated as if they wers non-fugitive materials and are carelessly left under illuminrition

containing ultraviolet light for extended prriods o f time (Berrhel.B.).

Esccssivc. hmt must bc avoidrd (El1is.M.H.. er ai. ( 1 ) 1999). Most driylight fluorescent pigments withstand

trrnperritures up to 176'C (350SF) for 5-30 minutes only with slight colour deteriorition. but the resins in

the pigments soften o r melt at temperatures betureen 70°C ( 15S°F) and 170°C (33S°F), and may decompose

below 200CC (39Z0F). (Smith.T. 1982) (Strcitel.S.G. 1995. pp.603-603) (Voedisch.R.W. Pigrtiertr

Hnricllrook v. 1 . 1973 ).

Recording and Reproduction of Daylight Fluorescent Colours

D>xs usrd for colour photography are not capable o f rsproducin: daylight fluorescent c o i o u r s . ' ~ h e r e is no

u . 3 ~ to photogrriph daylight fluorescent colours propsrly. As a remsdy for this problem, a swatch can be

made uith a marching colour and stored in the dark (ShinerJ. 1999).

In md3iy-5; design world, there are many sofnvare choices to achieve daylight fluorescent colours, although

the colours o n the cornputer monitor may not be exactly the sarne with daylight fluorescent pigments.

Probably thc phosphorous colours of the RGB monitor '%simulate the daylight fluorescent pigment colours

the most closely above al1 kinds o f colour media such a s fluorescent markers. papers. and so o n (Desigtiittg

~ c . i r l i Dax-Glo Color. 1998. p.21).

[ S The hue of driylight fluorescent pigments can be reproduced but the brightness (value) of daylight tluorescent pigments that exceed 100 5% in reflectance cannot be reprcsented by non-fluorescent dyes. It is irnpossiblc to distinguish daylight fluorescent colours from non-fluorescent colours on photographs. This \\.as expcricnccd during the research for this thesis. 1') Thc RGB system is uscd for regular television monitors and computcr monitors (Levkowitz.H. 1997).

APPENDIX IV.

Tables

Table 1. General Solubility Characteristics of Standard Organic Fluorescent Pigments

GI> cols Dici fi' Icric _si> col Diprop Icric gI> col

Acctonc Ilfclli! l ctli! 1 kcionc Isoplioroiic C!.clol~sa~iorlc

EiIi? Icric gI? col f-{cl! Icric gf? col

Eth? I ;irii! l kcioiic Diisobut? l hcioric

Lliricrril spirits trLf&P niphiliri Hc.uncs. riiiscd S> Icllcs SC- 100 i KB \-;iltic 0 1 )

~Mctii! Icric diIoridc Tnclilorocili~lcric

Dibtii~ l plirlnlm Dioc[> l phil~A,îtc But! l bcri~? I plti;daic (Smi icilcr I (Al 1 Di isobui! l adip;itc n-EifiyI tolucnc sulplion?niidc Polyncnc plnstici~crs. \xious (Sriniici/rr X )

- Pigmentation of Fluorescent Paints P.grnent Handbook vol 2. P 145

Table 2. Vehicles Suitable for Pigmentation with

Organic Fluorescent Pigments

Pol! :iriiidcs

C! clizcd rubbcr Cliloriruicd rubbcr SI? lcnc buiadicric nrbbcr

Pigmentation of Fluorescent Painrs Pigment Handbook vol 2. P 146

Table 3. Dyes as Components of Daylight Fluorescent Pigments

rcddisli \ iolcr bluish pink bluish pink

:\riii~~~)rl;~pli~ll;~liriiidC AZOSOI Briliianr (CI SoI\.cnr Ycllo\\ 44) grccnisii yAlo\\ Brillirini l'cliou (CI Solvcni Ycilo\\ 44) grccriisli >-cllo\s Brilli;irt1 Sulpho Flavinc FFA (CI 22205) grccnish yclIo\v 4-aniino-N-plicriy1n;ipht hiliniidc

Vozd1sch.R W Pigment Handbmk v 1 1973 p893

Vermont SIRI, Toxicology Report.

Table 4. Manufactures of Daylight Fluorescent Pigments

Ihric and C'o. (Londoii, U.K.)

I>;I? -CiIo Color Corpontion (Clcvclnrid. OH. U.S.A. i Da!-G lo J:it.loricckc Skl;ini?- Dcsna (naiiori;ilii! iiribnou n) B;illorini Bcads Liu [cl Cliciiiicnl Corp ( Skokic. III . U.S. t l .1 Opiichroriic

LcFr,iric :irid Boiirgcois (Fnncc) Fl:isli Flo Nippon Kciko Kngaku Co.. Ltd. (Tok! o. J:ip:in) Nipiiori Sliokiibai (Osda Japan) Siriloihi Co.. Lid. (K'minkura. Japan) Kndi:irit Color. Di\.ision of Magnidcr (Eli/abctli. Nj. U S.A. ) Visiprint Aquabcst

U.K. Scung (Busiri. Kom) \\'iridsor and Ne\\ ion (England)

Tttcrc arc s~itdl iiiriniiT;icturcrs in Chini. India Russix and Bm~il. E3:illorini Bcads arc I ~ i d rrcc luniincsccni glass bc;ids uscd \torld\t idc for rcflccti\-c road signs.

(Distribtitcd b! G1:isscspon Ltd.. Czcchoslo\.~?kia) . Tlic ni;iniifnctun.rs riiçnlioncd abo\c producc piy~ic'nts. Tl~c'si' pign~crits t11aj bc sold undcr rlic ii;iriic of rlic piyiwrir iii;iniifiictttrcr or uidcr ihc iinriic of LIK distributcr.

Martindil ,M G 1988

Streite1.S G 1995 p586

Voedisch,R W Pigment Handbook v 1 1973 p899

Table 5. Colour Spectrum

The hue wavelengths of the spectral colours and the complementary wavelengths of the nonspectral colours.

Color nanes h'iie Hue i?elative for l i ç h t s r wave- cornplemn- 1 u e i -

length tary wzve- n a s i Z y range l e n g t h ( S e c t .

range* 4 - 7 1 [ n m l [nml

Agoston,G.A. Cdor Theory And ils Application in Art and Design, 2- ed. 1987. p. 19.

Table 6. Colour Mixture

Ocirigc Oct11gc

Green-?cllo\s Grccri-~cllou Bitiisli g r c m --- -- B luc-grccri Grccriisli bluc Pi~rplc-bl ~ I C Purplc-bluc Rsd-purplc Rcd-piirplc

Scpnicd I Iiics Rcd and Grccri Ycllots Ckcn aiid B li~c B liic-grccri Bliic ;ind Rcd Pu rplc Ycllo\\ ;ilid BIii+grcci~ (C! :in) ----- Rluc-grccn m d Purplc ( kl;igcni:i ) -- Purplc (hlngcnini aiid I*cilo\s ---

C'oriiplcriiciii;in I ! ~ C S

Ycl i~ \ \ nrid Bluc X c i i ~ n l Bliic-prccrt m d Rcd Nciilnl Piirplc aiid Grccn Nciii ml Rcd and Eli~ci-grccn (rii i i iris Kcd) -- Green and Purplc (riiiriiis Grccn) ------ Bliic arid \ - ~ I O \ \ . ( r i t inlis E3 l u ~ ) ---

---

Grcc11 8 1 tic Rcd

Color in Business, Science, and Indüstry 2nd ed p 68-69

Table 7. Fifteen Causes of Colour

Trmsitions In\.ol\ing Ligand Firld E f k t s

I'r;iiisiiioii-iiic1;11 Conipo111Y1s tiircpoisc. cliroriic gccri. rliodorii[c. :imriic. coppcr p;iiiri;i

Tr;iiisiiiori-iiici;iI Iriipiintics nib! . criic~iid- :iqurirrlririiic. rcd iroii orc- sonic fliiocsccricc and lascrs

Trinsitions i3efwcr.n Molc~ular Ohitr ls

0rg;iriic Conipoiinds niost d! CS. inosi biological color,iiions. SOIIIC fluorcsccricc and lasers

C1i:ircc I'cirisfcr bluc sipptiirc. riingriciiic. I;ipis 1;uiiri. ultctni~nnc. clironic ycllou. fJnrssinn bliic

Trmsitions fn\.ol\.ing Encra Bands

Xlcilils coppcr. sil~cr. gold. iron. brriss. p>.nic. mb! glass. pol! ztirornaiic glnss. pliorochroiiiic glass

Piirc Scriiicoridiiciors diaii;ond. silicori. glcnri. ciririabar. \.crniilIiori- cndniiuni >,cllo\t. cadniiurii ormgc

Uopcd Scriiicondiicrors bluc ciiamond. ! cllou- diaritond liglircrnilting diodcs. sonic Iascrs arid pliosphors

Coloiir Ccriircs anicthys~ sniok~ quqm. dcscrt anicih! si glass. sonic flluorcsccncc and laxrs

Gcï~mctrical w t l Phyicül Optics

DisFrsi\ c rcfcicriori pnsrii spccinm. rdiribou.- halos. sun dogs. grccn fl:isti- fin-. irt gciiisioncs

Scmcring bluc sk:.. moan c~.cs . ski. buticrilics, bird fatiicrs.

rcd siinsct. R3n~1n scaiicriiig I ri~crfcrcricc oil slick on \\arcr. sonp bubblcs. coatirig on canicn Icnscs.

soriic biological colours D~frrxiior~ dirhciiori grrilings . opd. :iurcolc. glon-.

sornc biologicnl coloiirs. nion liquid cn.stals

Color Klrk-Othmer Encyclopedia of Chernical Terhnology 4th ed voi.6. p 861

Table 8. Instrument List for Experimerits Fading, Reflectance and Excitation-Emission Measurement. and Identification at t h e Crinahan Cunservaliori iristitute and Queen's University

Spc.crropliotoriictcr: CARY 3/U V-Viriblc Spcciroplioronicicr (Vnrian) (P .c .wa 0 ( n ) x ~ 2 0 )

Iriicgciiiri~ lighirricicr: ELSEC INTEGRATING LIGHT METER W P E 700

( Licllcriiorc Sci. Eiig. Co. Oxford) (N.M.C./M.N.C No. 5IXS7)

[ . i i \~~~ctcr optiçori cal-LIGHT JOO/ModcI 40OF

(Optikori Corpontion L-id.. Waterloo. ON. Crinldli) (P.C.H.it 273290)

t 'i* rtio:iitor- ELSEC I!V ?\IONITOR r Y P E 762 (ELSEC Ouford. IK i (P.C. k1.g Do()OG672)

Li V l;ittip ! I~iridlicld): Spccimlinc: BLE-2ZoB SpcctronicsAJV biilb. BLE05D/i\.liiic light bulb

Fliiorcsccr~i lig!ii b;iiA. 148.Sîms 127cii~~30crii/iiiicnor. 17 I .5cnis l.~5cnisi5ciii/cslcrior. 1'1 long biilbs. I! ood, pinicd \r hiic. Iconsirucicd at CCI)

Fi~~orcscciii ligl~t bulb (dnylighr t!pc ): VITA-LITE3DURO-TEST JOW. 1ZOkni i U.S.PatNo. 3.670.103 npid si. prchcat)

Hiiriiidir> clertibcr (2 sels): SOcrn\;50crns IOcni/tntcrior. 52cn~x52cnis 1 Icni/csicrior. Jrnnilpnncl ihickiicss. soda dnss (for N indow cic. 1. si ticon nibbcr ;ind it.a.dpskci. silic;) gcl (consrnicicd ni CC1 )

Table 9. Sample List - Sunlight Exposure

l i r ; i r d C'oluiri T I I I C ~ I I C ~ ~ 11:kl .-krori> I I I

Sraridard \Vfiitc Ccciniic Tilc hfcnsiircd n-ith Ci V filter Xlcisiircd u itlioiit U C' filtcr

N o Esposrirc No Esposiirc

N o Esposiirc Nu E\posurc

LFOrl) l LFOfl2 i,FOlf)3

LFOrOJ No E-~posurc LFOrO5 No Espsurc

C W I

- in - OUI

Table 10. Sample List - Alternative Settings Exposure

N R s-')( Sliirikolitc

no filtcr rio liglii NKS-')O

Shiikolitc rio filtcr no hglit 110 csposurc

NRS-O0 Slii nkolitc no f i l m

iio tiglit

NRS-O0

Shi iikolitc no f i lm rio Iiglii rio z~posiirc

Wnllxk's FI tiorcsccnr itiick WFOp 1 0 no coritrol no f i l m 60 % of original

Sludcii~ Ocirigc WFOp I i no coriirol rio Il Iicr 70 'Ki of onginal

.Acc l i s \VFOpl 2 no control no fiircr 80 1.;; of or-igirint \\YOpI 3 rio conrrol no filtcr WI "4 ofonginril NrFOp 1 4 no control no csposurc

IV;illxk's Flirorcsccnt ihin LVFOdIG no corirroi no film GO 94 of original Siiiderii Orringc WFOd17 no control no filtcr 70 % o f ongind Acn.lic NrFOfl)X no control no f i k r 80 % of ongirind

WFOtl19 no coritrol no filtcr ')O ?/u of original WFOrl O no coiitrol no csposurc

Sinndnrd Wliirc Ccnniic 'l'ilc hlc;istircd \\ itli UV filicr Llcnn~rcd witlioiit C; il filtcr

Table 1 1. Sample List - Excitation/Fluorescence Wavelength Measurement

Fliiorcsccni Bliic

Fliiorcsccrir Circcri

Fiiiorcsccrir l'cl Io\\

FI iiorcsccnr Oniigc

Fl iiorcsccrit Rcd

Fiuorcscctil Pirik

Fluorcsccnt Violct

Table 12. Sample List - Identiiying Daylight Fluorescent Materials p. 1

C.olour tir~clcr ~ ; I V I I ~ I I L I J \ ' Iliiorcscciicc Coloururidcr UV - - - - - - - --

Possi bl! )'CS

Possihl? \'CS

No Ycs

Possibl! Ycs Ycs

Ycs No

Ycs 50 No

Prob;ipl? No

Posstbl! Ycs No Xo

No

No Possibl! Ycs

Possibly Ycs .A litllr:

No 50 Ycs No

D;iA bluisli grc? Li$it biuisli grc! D;irk gnicn Grccriish ! cllot\ Sniiintcd ! clIo\\ P;islcl or,irigc 0r;ingc (darkcr iIim Cosniic Orringci Vcp dark rcd Rcddish o n n s c Vioict Purplc

L'CF- d;irk \.icrlct or blxk Drirk biuisli grc?. Grccriish grc? Sligtiil?- grccnisli lishi grcy Dnrk grccnisli SE?

Brou nish ycilo\\ -grccn S;iturdtcd Ycllow Omngc Bright ornngc û;irk rcd D;irk nirigcnin Pastc\ onngc

Purplisti grc?

Grcy Violci-bluc B l u c - ~ C C I I gr^!.

Ycllou~isti brou I I

Pinkish iight grcy Pink Dmic pink

Table 12. Sample List - Identifying Daylight Fluorescent Materials p. 2

(.'o!~!!r wdcr dy. !igh; l i Iliiorcsccncc Colo~ir undcr Li\'

Ptiints

\i':iIi;ick's Pai ru Brise (Tr~nsprirciir i \tr:illack's Lcniori Ycllow.

\L'rill:ick's Fliiorcsccni Ycllo\\

\t';illnckts Fluorcsccnr Onngc !Vnllnck's Fluorcsccnt hfagcniri Liqtiirc\: Fiiorcsccn! Bluc

L-iqiriic\: Fluorcsccnk Grccri

L.iqiiiic\: Fliiorcsccnr Ycllou Liquilcs Fliiorcsccnf Ormgc

L.iqiiiic\: Fliiorcsccrii Rcd

L-iqiiitcs Fluorc~ccni Pink

)-CS

No No

No

No Ycs Ycs Ycs

Ycs Ycs

Ycs Y CS

Y CS

Ycs

Ycs

(Bluc and orlicr colotirs) \Vliiic pins Y CS

Tnnsparctii. iio coloiir

Dark bmvn Grccnish ~ c l l o u .

Onngc Pinkisli rcd

Sliglii Violci-bluc

P:isicl gi-cc11

Pnsrcl 'cl lo\r

Ocingc Onngc

( rcddcr riciri Liquitcs Fluorcsccot Omngc~ Omngs

(simi' u ith Liqiiircs Fiiiorcsccnt Rcd)

Purpliah pirik

P:isicl bliic

Bliic pans Possibl~ Ycs Bluc \'cllu\\ p;ins Possibl' Ycs Smintcd > cl Ion

Table 13. Bluewool Standards Fading Monitor for Sunlight Exposure

Oli~c-\\ool Niinibcr D m Pcrccpitrl~ Eidcd D:i! s Esposcd io Siirili ytit

Vo I IO J t i l ! 1 O'N 7

No. 2 20 Jul! IWO 0

No. 3 27 Jul? lC)W i 3

Ko . 4 04 Augiisi IWO 2 1

No. 5 1 7 Scpicnibcr IWO 65

No. O 0.3 ~cbnirip ~ o ( n ) Z( 14

No 7 NOL f:idcd 'as of 0 7 Jul! Z o o 0

So s Soi fiidcd ris of (17 JiiI! 2ooo

Table 14. Factors for Intemrence Filters

Standard White Ceramic Tile Rcflccmncc w ï ~ h i nlcrfcrcncc Fil tcrs

(A) Filicr bmdpss [nm J

P d pl01 (C) Wavclcnglh Inml ID) Rcflcctancc l%J

:F) Rcgular rcflcctancc 1x1 ai pcak \~a~c lcngth (p070700 I )

Table 15. Monochromatic Excitation of Fluorescent Paints p. 1

Sriitiplc Filtcr Func~ion Basclinc Emission Pcak Fiuorcsccncc bandpass p d c (%J hcight 1x1 as % rcflcctancc

WLYrt15 400 nm (no ligiit)

450 nrn

L W r O l J O nni (sunlight)

150 nm

WFYrOS .)OC) nm (no lightl

150 nni

JSX nni

l F O i i ) l 400 nm (sunlight)

150 nni

WFOrO5 4OO nm (no light)

150 nrn

488 nrn

Table 15. Monochromatic Excitation of Fluorescent Paints p. 2

Srimplc Filtcr Function Basclinc Eniission P d Fluo rcsccncc bandpiss pc;ik (%j heighi (%J as % rcflcctancc

WFklrtil 4OOnm (sunlight)

450 nm

W W r O 5 W n m (no light)

450 nm

LFOrOI 4WJnni (sunlight)

450 nm

LFCho5 400 nm (no lighi)

450 nrn

488 nni

LFOg03 400 nm (no light)

450 nm

Table 16. Effectiveness of UV F ilter Against Paint Colour Fading (Altrenative Settings Exposure, 26 May 00)

Exposure Samples Reflectance Relative Relative Relative conditions at 650 nm [%j peak height fading rate fading speed

(Graph 46) NRSSO, RH5O0/0: UFRpOl O

Shinkolite, RH50%: UFRp02o no UV filter. RH50%: UFRp03o no light, RH50°h: UFRp04o no exposure: UFRpO9o

(Graph 47) NRSSO, RHOoA: UFRpOSo Shinkolite. RHOOh: UFRpO6o no UV filter, RHOOh: UFRp07o no light, RHO%: UFRp08o no exposure: UFRpO9o

(Graph 48) NRSSO, RH5096: WFOp01 O

Shinkolite, RH50%: WFOp02o no UV filter, RH50°h: WFOp03o no light, RH50%: WFOp04o no exposure: WFOpO9o

(Graph 49) NRS90, RHO%: WFOp05o Shinkolite, RHOOh: WFOpO6o no UV filter, RHO%: WFOp07o no light, RHO%: WFOp08o no exposure: WFOpO9o

APPENDIX V.

Figures

MacAdam Limits

Fig.

f ig. 2. Fig. 3.

Fig. 1. Locations of daylight fluorescent colours on the CIE chromaticity Diagram with MacAdarn limits at each lightness (luminance factor). (Voedisch,R.W. Pigment Hanbook vl . 1973. p.898.) Fig. 2. CIE 1931 (x, y, Y) colour space for light emitted by luminous objects. (Ag0ston.G.A. 1987. p.106.) Fig. 3. CIE 1931 (x, y, Y) colour space defined by MacAdam limits for non-luminous objects under CIE U C type of illumination. (Agoston,G.A. 1987. p.106.)

Fluorescent Materials

Fig. 4.

Fig. 5.

Wavclengih. nrn

pyridine furan thiophenc pyrrole

Fig. 6. quinoline isoquinoline indole

Fig. 4. Fluorescence excitation and emi::sion spectra for a quinine solution. (Skoo9,D.A-, et al. 1998. p.359.) Fig. 5. Materials that are non-fluorescent when there is no substitution, (Skoog,D.A., et al. 1998. p.361.) Fig. 6. Materials that are fluorescent without substitution. (Skoog,D.A., et al. 1998. p.362.)

Fluorescent Brighteners

Fig. 7.

Fig. 7 (a) - (i). Molecular structure of fluorescent brighteners. (Munay,S.G. 1996. pp.185-186.)

- 176 -

Fluorescent Dye's Excitation-Emirsion 30 Spectnrm

Fig. 8.

Fig. 8. Three-dimensional arrangement of excitation wavelength, emission wavelength and ernission intensity. A: emission wavelength range 370-700 nm. 6: excitation wavelength range 370-430 nm. Vertical axis: emission intensity. The fluorescence emission range of the specimen dye is similar to the emission range of Polish cochineal. (Wallert,A. 1986. p.153.)

- in-

Colour Diagrams p. 1

Fig. 9 (a).

Fig. 9 (a). Two dimensional colour diagrams in chronological order. (Genits8n.F. 1983. p21.)

- 178 -

Cofour Diagrams p. 2

Fig. 9 (b).

Fig. 9 (b). Three dimensional colour diagrams in chronological order. (Gerritsen,F. 1983. pp.22-23.)

- 179 -

Colour Diagmms p. 3

Fig. 9 (c).

Fig. 9 (c). Three dimensional colour diagrams in chronological order. (Gemtsen,F. 1983. pp.22-23.)

- 180-

Colour Diagmms p. 4

Fig. 9 (d).

Fig. 9 (d). Three dimensional colour diagrams in chronological order. (Gemtsen,F. 1983. p.24.)

- 181 -

Natural Colour System

Grrentsh y Rtdd~sh yel(ows I yctlows

GZOY G70Y

Fig. 10. Fig. 11.

Fig. 12. Fig. 13.

Fig. 10. Hering hue circk. (Agoston.G.A. 1987. p.258.) Fig. 1 1. NCS hue circle. (Agoston,G.A. 1987. p.134.) Çig. 12. NCS hue triangle. (Agoston,GA. 1987. p.136.) Fig. 13. NCS wlour solid. (Ag0ston.G.A. 1987. p.135.)

Ostwald Colour System

1s 10

Fig. 14. Fig. 15.

Neutra1 gray a(W) c c 9 I 1 n P ( B ~ )

Pure white 89.0 56.0 35.0 22.0 14.0 8.9 5.6 3.5 Pureblack 11.0 44.0 65.0 78.0 86.0 91.1 94.4 96.5

Fig. 16.

Fig. 17. (a) Fig. 1 7. (b) Fig. 18.

Fig. 14. Osîwald hue cide. (Agoston,G.A. 1987. p.125.) Fig. 15. Ostwald colour solid. (A9oston.G-A- 1987. p.124.) Fig. 16. Percentage of pure white and pure black in the Ostwald neutral greys. (Ag0ston.G.A 1987- p.126.) Fig. 1 7. (a), (b). Two-letter colour notation of Ostwald colour system. (Agoston,G.A. 1987. p.126.) Fig. 1 8. Verücal cross section of the Ostwald colour &id. (Agoston,G.A. 1987. p. 124.)

Munsell Colot System

Fig. 19.

Fig. 21, - I c h m r m _ t--

Fig. 19. Munsell Hue Circle. (Agoston,G.A. 1987. p.118.) Fig. 20. Horizontal cross section of Munsell color space at Munsell Value 6 (luminance factor Y = 0.30). Outer penmetre: MacAdam limit for Munsell Color Circle (CIE ILL C). lnner perimetre: available gamut of Munsell Standard Color Chips. (Agoston.G.A. 1987. p.118J Fig. 21. Vertical cross secüon of Munsell color space. Perimetre: MacAdam limit for Munsell Color Spa- (CIE IU C), Dots: available gamut of Munsell standard color chips. (Agoston,G.A. 1987. p.119.)

Colour Specincation with Trlstimulus Values

Fig. 22. Three primary coiours (red .green and Mue) are superimposed to mix the coloun and the amounts of the primary coiours are adjusted so that the colour of the mixiure becornes identical with the specirnen. (Johnston,R.M. 1973. p235.)

Chromaticity Oiagrams p. 1

Fig. 23.

Fig. 24. Fig. 25.

Fig. 23. Kelly's map for coiours of luminous objects on the CIE 1931 (x, y) chromaticity diagram. E: equai power point. C: CIE ILL C, Dos: CIE IL i &. The colour names and the abbreviations are show in the table. The numbers on the spectnim locus are the wavelengths of monochromatic lights and the numbers with C on the purple line are complementary wave lengths of the colours. (Agoston,G.A. 1987. p.67.) Fig. 24. CIE 1931 (x, y) chromaticity diagram, or Maxwell triangle, based on the three irnaginary primasr colours (R, G, 6). R: red. G: green. 8: blue. (Agoston,G.A. 1987. p.56.) Fig. 25. CIE 1976 (u', v') chrornaticity diagram. Curves show the colours of constant Munsell Chroma (8, 12 and 16) at Munsell Value 5 (luminance factor Y = 0.2). C: chromaticity of CIE ILL C. (Agoston.GA.1987.p.s4.)

Chromaticity Diagrams p. 2

Magenta

Fig. 26. Fig. 27.

Fig. 28. Fig. 30.

I

Fig. 31.

Fig. 26. Maxwell Triangle (chromaticity diagram). (Agoston,GA. 1987. p.49.) Fig. 27. Notation of the colour S. (Agoston,G-A. 1987. p.50.) Fig. 28- Lines of constant x: fractional amount of primary red (Maxwell triangle). (Agoston.G.A. 1987. p.50.) Fig. 29. Lines of constant y: fractional amount of primary green (Maxwell triangle). (Agostori.G.A 1987. p.50.) Fig. 30- Lines of constant z: fractional amount of primary blue (Maxwell triangle). (Agoston.G.A.1987. p.%.) Fig- 31. Maxwell Triangle (chmmaticity diagram) as a right triangle. (Agoston.G.A. 1987. p.52.)

Power Spectm of Illuminants

Fig. 32.

wawlenpin Inml

Fig. 35.

-1% N

Fig. 33. i.*.i*ngill IMd

Fig. 34.

Fig. 36.

Fig. 32. E: the equal power distribution. 1: direct sunlight. II: north-sky light. (Agoston,G.A. 1987. p.23.) Fig -33. Tungsten-filament lamp. (Ag0ston.G.A. 1 987. p-22) Fig. 34. Dayiight type fluorescent lamp. (colour temperature 6000 K) (Agoston,G.A, 1987. p.22,) Fig. 35. Cornparison of the CIE standard illuminants. (Agoston,G.A. f 987. p.25.) Fig. 36. Cornparison of the CIE standard illuminants. (Ag0ston.G.A- 1987. p.25.)

CIE Colour Space - CIE L'u'v* and CIE L*a*b*

Fig. 37.

Fig. 39.

Fig. 40.

Fig. 38.

Fig. 37. CIE LUV 1976 colour space. The u* axis and the vm axis indicate the horizontal plane at the metric light ness L* = 50. (Agoston,G.A. 1987. p.1 08.) Fig. 38. CIE LA6 1976 colour space. The a' am's and tha b' axis indicate the horizontal plane at the metric light ness L' = 50. (Agoston,G.A 1987. p.108.) Fig. 39. CIE LUV 1976 colour space showing the CIE L*umvg wburspecification of a colour that is represented by the point Pl (Le = 50, u* = 12, vg = 26). Pz (Lez, U'Z, ~ ' 2 ) shows a general .qmcificaüon of a colour. Colour difference between Pl and Pz is the distance between Pl and P2 in the colour space. (Agoston,G.A. 1987. p. 109.) Fig. 40. CIE LUV 1976 colour space showing the metnc Iightness L', the mettic chrome Cew and the metric hue angle Ho, of the colour Pt . (L' = 50, ug = 12, v* = 26). (Agoston,GA. 1987. p.109.)

The hue directions of the u* and vg axes (red or green, blue or yellow) in the Fig. 40 apply al1 four figures.

Fig. 41.

Fig. 41. Madder lake pigment under different illumination. Il-A: illuminated by an incandescent lamp (CIE ILL A). Il-C: iiiuminated by dayiight type lamp (CIE ILL C). (Agost0n.G.A. 1987. p.34.)

- 190-

ASTM form 38

Fig. 42.

Fig. 42. The size of the ASTM form 38 is 19.40 x 28.95 cm, approximately the letter size.

APPENDIX VI.

Graphs

O O (O w

O CV

( m u e p a ~ a ~ % se)

Graph 7. Standard White Ceramic Tile Reflectance: before and after experiment

83 i l I I r I I 1 O 1 O0 200 300 400 500 600 700 800

Reflection Wavelength [nm] -- r' CWo 14-Jul-99 - . CWo O F J U C O ~

Graph 8. Wallack's Lemon Yellow thin 03 (sunlight) Reflectance: before and after experiment

+ I 1 1 1 i 1 1 1

O 1 O0 200 300 400 500 600 700 800

Reflection Wavelength [nm]

Graph 9. Wallack's Lemon Yellow thin 04 (not exposed) Reflectance: before and after expariment

300 400 500

Reflection Wavelength [nm]

Graph 10. Wallack's Fluorescent Yellow thin 03 (sunlight) Reflectance: before and after experiment

- ,. ... .-.-.-.--..-. - .-.-. . -. . . ~ - .-.. .. .- . - . . . . .. . - .. .- - .- . .. -. - ... -- - . - . -

Reflection Wavelength [nm]

Graph 14. Wallack's Fluorescent Magenta thin 03 (sunlight) Reflectance: before and after experiment

Refelction Wavelength [nm]

Graph 15. Wallack's Fluorescent Magenta thin 04 (not exposed) Reflectance: before and after experiment

120 - n s 8 IO0 - f O, 80 -. E al E

60 -

40 - -

20 .'

O -

4

1

-------- I ------.-.. ---------'-----r-----..--.-. --.....-..------ 1

! 1 1 I -- - . - - - - - - - - --..-- -1 ------- .- - --.; 4

6 l 4 l . - - - - - - - - - - - . - 1 a - - - - - ---- +

I I

1 1

I

- .---.- .----.-.--.----lv---.-..----. I . .. - ...-, .C.*-...( l

t t 1

I

* i - (C \---W.-- -.-A 9.; 8 1 4 I

4 ' b 1

- 4 ---.--.-------..-.--------"- ---..--.--.- .----- ----. 4 \ r'

.*a. 0-.....u4

I I 1 I I I 1

O 100 200 300 400 500 600 700 800

Reflection Wavelength [nm]

Graph 17. Liquitex Fluorescent Orange thin O3 (sunlight) Reflectance: before and after experiment

Reflection Wavelength [nm]

Graph 18. Liquitex Fluorescent Orange thin 04 (not exposed) Reflectance: before and after experiment

Reflection Wavelength [nrn]

Graph 24. Wallack's Fluorescent Orange thick 09 (not exposed) Reflectance: before and after experiment

. . . . . . . . ........... ,-.- .. . . - -

300 400 500

Reflectoin Wavetength [nm]

Graph 27. Wallack's Fluorescent Orange thick 10 (lamp) Reflectance: before and after experiment

Reflection Wavelength [nm]

Graph 28. Wallack's Fluorescent Orange thick 14 (not exposed) Reflectance: before and after experiment

Reflection Wavelength [nmj

Graph 29. Wallack's Fluorescent Orange thin 06 (tamp) Reflectance: before and after experirnent

300 400 500

Reflection Wavelength [nm]

Graph 30. Wallack's Fluorescent Orange thin 10 (not exposed) Reflectance: before and after experiment

300 400 500

Reflection Wavelength [nrn]

Graph 31. Wallack's Lemon Yellow thin 03 Fading (sunlight)

Graph 32- Wallack's Lemon Yellow thin 04 Fading (not exposed)

Graph 33. Waltack's Fluorescent Yellow thin 03 Fading (sunlight)

Graph 34. Wallack's Fluorescent Yellow thin 04 Fading (not exposed)

' * 400 nm -45Onm - - - - / 480nm * 500nrn

1-520 nm C. 620 nrn - 660 nm

Graph 35- Wallack's Ffuorescent Orange thin 03 Fading (sunlight)

Wallack's Fluorescent Orange thin 04 Fading (not exposed)

Graph 37. Wallack's Fluorescent Magenta thin 03 Fading (sunlight)

Days Exposed

1- 620 nrn 9 650 nm - 700 nm 1

Graph 38. Wallack's Fluorescent Magenta thin 04 Fading (not exposed)

x - -400nm -430nm - - - - 550 nm a 610 nrn

-620 nm 0 650 nm - 700 nm

Graph 39. Liquitex Fluorescent Orange thin 03 Fading (sunlight)

150 200 250 300 350 400

Days Exposed

Liquitex Fluorescent Orange thin 04 Fading (not exposed)

Graph 41. Liquitex Fluorescent Orange thick 01 Fading (sunlight)

Days Exposed

Liquitex Fluorescent Orange thick 03 Fading (not exposed)

Graph 43- Utilac Fluorescent Red thick 03 Fading (lamp, no Citer, RH 50 O! )

Graph 44. Wallack's Fluorescent Orange thick 03 Fading (lamp, no fiiter, RH 50 ./O)

150 200

Days Expcsed

1 400 nrn - 500 nrn -600 nrn - 650 nrn ,2 700 nrn /

Wallack's Fluorescent Orange thin 06 Fading (lamp)

Days Exposed

Utilac Fluorescent Red thick RH 5O0h Reflectance 26-y-00

Graph 47. Utilac Fluorescent Red thick RH 0% Reflectance 26-my4û

' NU=. Riîû%: UFRpOSo - ainidite. RHOSb: UFRpOGa

- m UV Mer. RW%: UFR@7o nolight. RH(39b: UFRp(38o 1 - - - - - n o v e : UFRpQBo i

Graph 48. Wallack's Fluorescent Orange thick RH 50% Reflectance 26-my-00

1

O 100 200 300 400 500 600

Reflection Wavelength [nm]

I -NRSSO, AH50%: WFOpOl O - Shinkolite. RH50%: WFOp02o i

i no UV filter, RH5046: WFOp03o -- - -.no light. RH5096: WFOp04o .

- - - - - no expasure: WFOpOSo

Graph 49. Wallack's Fluorescent Orange tihck RH 0% Reflectance 26-my-00

Graph 50. RH Sû% vs RH û% with UV filter NRS9û (lamp) Reflectance: Utilac Fluorescent R d Chick

Graph 51. RH 50% vs RH 0% with UV filter Shinkolite (lamp) Retlectance: Uslac Fluorescent Red thick

Graph 52. RH 5 0 Y vs RH @XI without UV filta (lamp) Reflectance: Utilac Fluorescent Red thick

Graph 53. RH 50% vs RH 0% without Iight Reflectance: Utilac Fluorescent Red thick

lai

Graph 54. RH- vs RH û% with UV filter NRSSO (lamp) Reflectance: Wallack's Fluorescent ûrange aiick

Graph 55. RH SU% vs RH Ci% with UV filter Shinkdite (lamp) Reflectance: Wallack's Fluorescent Orange thick

Graph 56, RH 50% vs RH 0% without UV filter (Iamp) Reflectance: W allack's Fluorescent Orange thick

1 - - - - - no UV fiRer. RHSI%: WFOp030 - no UV filer. RHO%: WFOq07o

I no eqmwre: W F O ~ O B ~ I

Graph 57. RH 50% vs RH û% without light Reflectance: Wallack's Fluorescent Orange thick

Graph 60. Liquitex Fluorescent Orange thick Excitation-Ernission (Sunlight Exposure)

c023nOOsun Baseline 100°/oT - - - c02 Jn00sun LFOpOl exposed jlI c02JnOOsun ---- LFOpOÎexposed -- -- O c02 Jn00sun LFOp03not exposed --- y- --..--- .-*---

O I 1 I I I I 1 1 1

O 1 O0 200 300 400 500 600 700 800 900

Excitation Wavelength [nm]

( a u e p a ~ a ~ % se) uo~ss!ui~

Graph 63. Alternative Settings Exposure Sarnple Paints Excitation-Ernission (thick, not exposed)

--- 1 ,-- . ..-... c2Qmy00as UFRpOQlUtilac Fluorescent Red - c29MyOOas WFOp09Mlallack's ~ l u o n s c e ~ ] ---

10

O 1 I 1 I 1 L 1 I

O 1 O0 200 300 400 500 600 700 800 900

Excitation Wavelength [nm]

Graph 66. Reflectance: Wallack's Paints on Arches (p0707001)

.. - - .. . .. . - L . .- . . . -. -. . . - - - - . . . - -. . .. . .. - . . ~ _ _, .- . . . . .. ...- . _ -.. .__^__.____ ... _ . _ < _ _ ..

Reflection Wavelength [nm] ---- ---- -

~ ~ Y ~ ~ w ~ ~ ~ a 3 2 o u t Fluorescent Yellow WFYa32o 1 A Fluorescent Orange WFOa32o Fluorescent Magenta WFMa32o - ----- -----.

0 0 0 0 0 0 0 0 0 0 0 o Q ) a D < r > m m c u - Y

(muepa~a~ % se) UO!SS!UJ~

r p . I ).

0. M S. 0. C e b. * t x ' * --. E -- Y -

b-.

I i:

0 0 0 0 0 0 0 0 0 0 0 o a o ( D u , * t o c u - F

( m u e ~ ~ a ~ oh se) uo!s!ui3

Graph 73. Standard White Ceramic Tile (filter bandpass 400 nm) Reflectance: monochromatic excitation

Reflection Wavelength [nrn]

Graph 74. Standard White Ceramic Tile (filter bandpass 450nm) Reflectance: monochromatic excitation

- - . .- . - . .

Reflection Wavelength [nm]

Graph 75. Standard White Ceramic Tile (filter bandpass 488 nm) Reflectance: monochromatic excitation

. -

Reflection Wavelength [nm]

Graph 77. Wallack's fluorescent Yellow th Reflectance: monochromatic excita

in 01 (sunlight) lion

. . . -4 J ---. .--..- . . . . ..-.-- --.-..---.- ................... . . . . . . .

Reflection Wavelength [nm]

bandpass 400 nm e070800 WFYr1400

..... bandpass 450 nrn e070800 WFYr1450

- bandpass 488 nrn e070800 WFYrl488 --------.

E E E C C C

E E E C C C

Graph 80. Wallack's Fluorescent Orange thin 05 (not exposed) Reflectance: monochromatic excitation

. ... .

Reflection Wavelength [nm]

-------- bandpass 400 nm eO70800 WFOr5400

..... bandpass 450 nm e070800 WFOr5450

- bandpass 488 nm e070800 W f OrM88

€ € € C C C

Graph 82. Wallack's Fluorescent Magenta thin 05 (not exposed) Reflectance: monochromatic excitation

bandpass 400 nm e070800 WFMr5400

..-.. bandpass 450 nm e070800 WFMr5450 bandpass 488 nm e070800 WFMr5488

Reflection Wavelength [nm]

Graph 84. Liquitex Fluorescent Orange thin 05 (not exposed) Reftectance: monochromatic excitation

---*--. - --.. . . . , -.. .-.. . .

Reflection Wavelength [nm]

bandpass 400 nm e070800 LFOr5400

..... bandpass 450 nm 6070800 LFOr5450

- bandpass 488 nm e070800 LFOr5488 -----

Graph 85. Liquitex Fluorescent Orange thick O1 (sunlight) Reflectance: monochromatic excitation

. . . . . . . . . . . . . . . .

Reflection Wavelength [nm]

---- bandpass 400 nm e070800 LFOpl4OO

..... bandpass 450 nrn 0070800 1 LFOpl450 bandpass 488 nm e070800 1- LFOpi488

Graph 86. Liquitex fluorescent Orange thick 03 (not exposed) Reflectance: monochromatic excitation

-.A- ...... --. - -,-- .- .-..- . .. ... ... - . ,

- . . - . - , .-----a-- * --.-.- - - .---m.- -.-----. - .. . .. . . .~ ~.

Reflection Wavelength [nm]

bandpass 400 nm e070800 LFOp3400

. . . . . bandpass 450 nm e070800 LFOp3450

- bandpass 488 nm e070801 LFOp3488 -----------

Graph 87. ASTM form 38 (blank) Reflectance V.S. Excitation-Emission

RefiectionlExcitation Wavelength [nm]

Graph 88. Arches (blank) Reflectance v.s. Excitation-Emission

1 O0 200 300 400 500 600 700 800 900

Reflection/Excitation Wavelength [nm] - - - - - - . - - - L--__.--C -._.._ --__-. ------ - - -

Reflectance p0707001 arch320 Emission c29myOOar arch 32 j I - - ------ - - . . -- - - - - - ------

Graph 91. Wallack's Lemon Yellow thin 03 (sunlight) Reflectance (corrected with a factor of 1.045) V.S. Excitation-Emission

ReflectionlExcitation Wavelength [nm]

006 000 OOL 009 00Ç OOP OOC 001 00 1 O 1 1 I I l 1 I I I

,

uo!ss!uq-uo!aeapx3 'S'A (SW* L JO loaael e q a ! ~ p a p e ~ ~ o a ) e a u e ~ 3 e l ~ e ~ (pasoxa aou) PO u!qa M O I ~ E , u o w q s,yaelle~ '26 i1de~9

Graph 93. Wallack's Fluorescent Yellow thin 03 (sunlight) Reflectance (corrected with a factor of 1.045) V.S. Excitation-Emission

1 O0 200 300 400 500 600 700 800

ReflectionlExcitation Wavelength [nm] ----

P Emission c02JnOOsun WFYr03 . a Reflectance x Factor w~~~~

Graph 94. Wallack's Fluorescent Yellow thin 04 (not exposed) Reflectance (corrected with a factor of 1.045) V.S. Excitation-Emission

I I 1 I 1 1

!

I

O 1

1 O0 200 300 400 500 600 700 800 900

ReflectionIExcitation Wavelength [nm] - - - - ----.-- - -_.----- - ........... - -

Emission c02JnOOsun WFYr04 - . - - - Reflectance x Factor W F Y ~ O ~ O ] ------- ---

Graph 95. Wallack's Fluorescent Orange thin 03 (sunlight) Reflectance (corrected with a factor of 1.045) v.s. Excitation-Emission

Reflection/Excitation Wavelength [nm] - - - - -.------ -

~ m ~ s s l o n 6 n 0 0 s u n WFOr03 - - - - Reflectance x Factor W F O ~ O ~ O ] ------- --- --- ---- .--

Graph 96. Wallack's Fluorescent Orange thin 04 (not exposed) Reflectance (corrected with a factor of 1.045) vas. Excitation-Emission

ReflectionlExcitation Wavelength [nm]

Graph 97. Wallack's Fluorescent Magenta thin 03 (sunlight) Reflectance (corrected with a factor of 1.045) V.S. Excitation-Emission

300 400 500 600

ReflectionlExcitation Wavelength [nm]

1 Emission c02JnOOsun WFMr03 - . Reflectance x Factor WFMrû3o 1

006 008 OOL 009 00Ç OOP OOC 002 O0 1 O

Greph 100. Liquitex Fluorescent Orange thin 04 (not exposed) Reflectance (corrected with a factor of 1.045) V.S. Excitation-Emission

-. - -- -. --- - - - - -. - - - - - . . - - . -

300 400 500 600

ReflectionlExcitation Wavelength [nmj

Graph 101. Liquitex Fluorescent Orange thick 01 (sunlight) Reflectance (corrected with a factor of 1.045) v.s. Excitation-Emission

l

O l

1 1 I 1 1 I 1 1 1

O 1 O0 200 300 400 500 600 700 800 900

ReflectionlExcitation Wavelength [nm]

Ernission c02JnOOsun LFOpOI Reflectance x Factor LFOpOlo 1

Graph 102. Liquitex Fluorescent Orange thick 03 (not exposed)

ReflectionlExcitation Wavelength [nm]

Graph 103. Wallack's Lemon Yellow on Arches Refîectance (corrected with a factor of 1 . O W ) v.s. Excitation-Emission

O 4 I 1 1 1 1 I I r l O 1 O0 200 300 400 500 600 700 800 900

ReflectionlExcitation Wavelength [nm]

Graph 107. Liquitex Fluorescent Blue on Arches Reflectance (corrected with a factor of 1.057) V.S. Excitation-Emission

Reflection/Excitation Wavelength [nm]

r Emission cO5JtOOLQar LFB2a32 - . Reflectance x Factor L F B ~ Z ~

Graph 1 10. Liquitex Fluorescent Orange on Arches Reflectance (corrected with a factor of 1.057) V.S. Excitation-Ernission

ReftectionlExcitation Wavelength [nm] -A- r Ernission ~ & I O O L Q ~ ~ ~ ~ 0 x 3 2 . - - - - Reflectance x Factor ~ ~ 0 2 a 3 4 -

OOL

Graph 1 il. Papaer - Astrobrights - 2 Reflec tance

300 400 500

Reflection Wavelength [nm]

. . . . . Astrobrights Cosmic Orange -f Astrobrights Rocket Red -f Astrobrights Re-Entry Red Astrobrights Fireball Fuchsia -f Astrobrights Mars Magenta - ---- Astrobrights Planetary ---.---.-.---.a Purple

Graph 120. Paper - Envelopes - 2 Reflectance

300 400 500

Reflection Wavelength [nm] ------ ------ ----.--

1 a Envelope Pink, pale Envelopr Pink, dark . - - Envelope ~ e d 1

K . ;

Graph 122. Wallack's Lemon Yellow thin 03 Fading (sunlight) 1 resetlweek

Light Dosage [MLxHr]

Graph 123. Wallack's Fluorescent Yellow thin 03 Fading (sunlight) 1 resetlweek

20 30 40 50

Light Dosage [MLxHr]

'--400 nm -450 nm - - - - 480 nm --A-- 500 nm - 520 nm -6 620 nrn - 660 nrn

Graph 124. Wallack's Fluorescent Orange thin 03 Fading (sunlight) 1 resetlweek

Light Dosage [MLxHr]

Graph 125. Wallack's Fluorescent Orange thin 03 Fading (sunlight) 2 resetdweek

1 l

i

Light Dosage [MLxHr]

I r: 400nm-440nm---- 530 nm * 550 nrn

Graph 126. Wallack's Fluorescent Magenta thin 03 Fading (sunlight) 1 resetlweek

O 10 20 30 40 50 60 70

Light Dosage [MLxHr]

'-400 nm -430 nm - - - . I

550 nm -610 nm: l-620nm 0 650nm -700nm l

Graph 127. Liquitex Fluorescent Orange thin 03 Fading (sunlight) 1 resetlweek

Light Dosage [MLxHr]

Graph 128. Liquitex Fluorescent Orange thick 01 Fading (sunlight) 1 resetlweek

I

2oo -6ie- ag,-- 1 7 I

4

- 150

-- £r, - -0 *-• + ---CL

I - * P . - . * - - * ---O*S 0

i I - z - * ___I

8 y++++ -- ----A--_ U

&-- &-A 1

% + + - + + -+ 4

t - + + + . - + - - + [ I ca

c. O j 0, - *-. - -.- - ---- - - - - - - - --. .c

@-- - - - i al

/ C -- - = 100 .. .--- I

1

l f i

? j -

50

O -O

O - 0 o 0 - 0- --- O -

P - a - x- +-x # 9 - - 4 -x x W.

O f 10 20 30 40 50 60 70 O

Light Dosage [MLxHr] P

,-400nm 0 5 0 0 n m - - - - 590 nm - 6 0 0 nm

- ' 610nm -0- 650nm + 700nm - - -

APPENDIX VII.

Glossary

Some nwds appeared in this thesis have speçid definitions in art conservation. in the colour industry and in othcr fields. Since the tcrminology of thsse words is not ctl\+,ays clear. thrsc terms arc dsfined in this glossary. specifically for this thesis. and rire listed in alphabstical ordzr.

AATCC: Arnerican Association of Textile Chernisis and Colorists t Fe1ler.R.L. 19S5. PA!).

Absolute humidity : The concentration of water vapour in the air. Absolutr hurnidity is independrnt from temperature bvhile relative humidity changes corresponding to temperiture change (Cassar.M. 1995. p.145).

Affinity: The capability of a papcr dyc to be bound to the cellulose fibre (Murray.S.G. 1996. p.178).

Afterglow: Visual luminescrncr: that continues after the rsciter radiation is rernoved. Phosphorescence (By1er.W.H. Pignierir Hnridbook v . 1. 1973. p.907).

ASThI: Arncrican Society for Testing and hlateririls ( 1992 Amirrc~l Book of ASTM S~unciards v. 6).

Blue-IVool Standards: A set of blue colour fabric s\vatshes tc, mrasure the ripproximstr lizht dosrigr on the surface. The swatches are dyed to have known lightfrtstnsss in varying degrees (Feller.R.L. 19S5).

Brightness: Lightness of object colour or illuminance of light (Agoston.G.A. 1987. p. I I ) (Levkowitz.H. 1997. p.7).

CCJ: Canadian Conservation Institute. Ottawa Canada.

Chroma: Vividncss of ri colour in the MunsrlI Color S>.srem. Thc ratio of the chromatic component in a colour that consists of a chromatic component (ri colour with a hue) and an achromatic compontm (a colour without a hue). Also called saturation or excitation purity (.\goston.G.A. 1987. pp. 13. 1 16) (Levk0witz.H. 1997. p.7). cf. hue. value

CIE: The Commission Internationale d'Eclairage (Agoston.G.A. 1987. p.3).

CIE L*a*b*: A colour specifïcation systern recommended by the CIE. Designates the degrces of thc lightness (or rnetric lightness): L*. the rcdness (or greenness): a*. and the yellowness (or blueness): b* of a colour in numerical figures. The calculritions for these figures are bascd on the CIE tristimulus values X, Y, and Z . that rire obtriincd through spcctrophotometry (Ag0ston.G.A. 1987. pp. 105- 1 1 1 ).

Colorimeter: Photorneter. It consists of a source. a filter. and ri photoelectric trrinsducer. as wcll ris a signal processor and readout (Skoog.D.A., et al. 1998. pp. 1 S 1 - 182). A colorirnctcr can give the CIE tristimulus values but nor a colour spcctrum (a distribution ofrcflection energy as a function of wvclcngth). ( 1992 Atirirrnl Book of ASTM S m h r d s v.6. E- 1347-90). cf. spectrophotometcr

Colorant: A colourful material that is uscd ro rive colour ro rinothcr maicrial.

Colorirnctry: Colour meaurcmcnt using :_ colorimctcr.

Colour nielisurcment: A rnethod to spcci t). or designrite solour objectively using an instrument.

Conservationist: A person who work to protect (or tu conserve) natural sites. wild lit2 o r the natural environment (Lot~gman Dicriot~an of Cotirer~zporap Etrgltsft new ed. 199 1 ).

Conscrvator: A profession thrit restores and maintains cultural heritage such as art ~vorks. documents and archaeological rnaterials. Ir may be b~ttc 'r 10 use an expression "art conservator" as a general occupritionril category o r designrite the specialry as "paper conservator," "painting conservritor" and so on. in order io prevent people from confusing s"conservator" uith "conserva~ionist."

Convcntional pigment: Whsn talking about tluorescenr pigment o r luminescent pigment. conventionai pigment rncrins "non-fluorescent" pigment.

Darkcning: A phenornenon of colour deterioration in which lighrness decrerisr=s and the colour becomes darkcr (E1lis.M.H.. et al. (1 ) 1999). cf. lightening, fading. ysllowing

Daylight: A type of illumination that rcsembles indirect sunlight in the light enersy spectrum. The CIE ILLD6.5 is one of the daylight type illuminrints (Agoston.G..-\. 1987. pp.21-25).

Daylight fluorescent: Having a propcny to discharge energy as tluorescence when the materid rcceivrs visible light or long wavelength ultraviolet lipht. The ernission of light does not continue after the illumination is rernoved (Voedisch,R.W. Pigmmr Handbook v. 1 . 1973. pp.89 1-892).

Day-Glo: The name of an Amcrican manufacturer specializrs in daylight fluorescent colorants. The Company name is used as if it is ri gcnerril trrm to indicate d r i ~ l i ~ h t fluorescent colours (De~ i~~ t t i t i g rc-irli Da?.-Glo Color. 1998) (E1lis.M.H.. et al. (1) 1999).

Dominant wavelcngth: The wavekngth thrit determines the hue of the coIour (Agoston.G.A. 19S7. pp.5S-59) (Levkowitz.H. 1997. p.7). The wavdength of the surnmit of the dominant (main) perik in the rcflectance spectrum (El1is.M.H.. et 31. (1) 1999). cf. excitation purity

Dyc: A colorant that is used ris a Iiquid solution and gives ri colour to rinother matcrial by adsorption on or absorption in the material. To give colour by using a dye. cf. pigment

DycstuE A material (or product) that is used 3s a dye (Joseph,M.L. 1986. p.330).

Electromagnetic radiation: A flow of minute particles chat vibrate while proceeding in a spricc or in materials. The wavelength and the frequency arc determined by the rimount of energy of the radiation (Hushirni.K., et ai. 1983. p.239) (Skaog.D.A.. et al. 1998. pp. 1 1s. 130).

Excitation: Making elecuons move to a hizher energy srrite in a substance by giving energy to the clectrons. The energy of the excited clectrons is lost either through non-radiarive reIrixation o r luminescence (V0edisch.R.W. Pignicrrt Hctridhook v. 1. 1973. pp.89 1-892).

Escitation purity: Purity of 3 colour o r saruration of a colour. On the CIE chromriticity diagram excitation purity is the closeness CO the spectrurn locus o r to the purplc linc (Agoston.G.A. 1987. pp.58-60). On 3 rcflectance spectrurn or on an emission spectrum. this is the sharpness of the dominant peak (El1is.M.H.. et al. ( 1 ) 1999). cf. dominant wavelength

Fading: A phenomcnon of colour deterioration observcrd as ri loss of saturation. h d i n g is oticn associated with increase o f lightnzss (lightrning). with incrcrtse of transprirency (loss of hiding po\ver), and sornctirnes also with hue shift (El1is.M.H.. et 31. ( 1 ) 1999) (Fcrl1cr.R.L. 1985). cf. darkening. yeIlowing

FBA: Fluorescent brightencr.

Fluorence: A glowing appearance of a colour. Fluorence crin be fluorescence but it can be an optical illusion (Evans.R.M. 1972. p.4). cf. fluorent

Fluorent: Having an appearance as if it is glowing. A fluorent materid is not necessarily fluorescent (Evans.R.M. 1973. p.4). cf. fI uorence

Fluorescence: Re-emission of c.lectrornrignetic energy from ri substance folIo\ving energy absorption. or luminescence that does not continue after the exciter is rernovsd. To the humrin eye. tluorescence continues only while the substance is receiving the excitation radiation. (Voedisch.R.W. Pignimx Hatzdbook v. 1. 1973. pp.S9 1-892). cf. lurninescencc. phosphorescence. reflectance

Fluorescent: Having an ability ro fI uoresce. o r to re-emir the absorbed energy as fluorescence. but not glowing in the dark (Voedisch.R.W. P i p e t i t Hnfirll>oolr v. 1. 1973. pp.S9 1-892). cf. Luminescent. phosphorescent

Fluorescent brightener: A dye for paper. textile, plastic and for detergcnt ta impan fluorsscencr to products or to laundry. Absorbs light at the short wavelength rsgion (300430 nm) frorn driylisht and emits violet or blue visible fluorescence. The bluish fluorescence of tluorescent brightener counteracts the yellowish tint. adds brighcness and makes materials appear \vhiter. Also called optical brightener. fluorescent brightening agent (FBA). optical brightening agent (OBA) and fluorescent whitening agent (EWA). (Murray.S.G. 1996. pp. 1 84- 185) (Schwunger.M.J. 19S9. pp.336, 312) (Singh,N. 1999. p.33).

Fluorescent brightening agent: Fluoresceni brightener.

Fluorescent whitening agent: Fluorescent brightener.

Frcquency: The number of vibration thrit occurs in a cenain pcriod of tirne. Frequency is reciprocal of wavelength of elsctromagnetic radiation (light). The unit for frequency crin be Hz (hertz. cycle per second) or s-' (reciprocal second). (Skoog.D.A., et al. 199s. pp. i 17- 1 18). cf. wavclength

Fugitive: Susceptible to Ioss of colour. Erisily frided. Not bsing li=httjst. Fugitive means the colour of the substance is unstable and has low resistance to environmenial stress including light. CC lightfastness

FWA: Fluorescent brightener.

Glow-in-thedark: Adjective CO indicate that the matenal is phosphorescent. The Iight re-emission is visible and long enough to be appreciated by people. (Vosdisch.R.W. Pigrrrerir Hundbook v. 1. 1973. ~ 3 9 2 )

l1ALS: A type of UV stabiliser.

Hiding power: The ability of a pigment to obscure its substrate. Opacity. Opaquensss.

liuc: A propèrty (attribution) of colour that makes a colour name such as red. green o r blue (Agoston,G.A. 1987- pp. 12- 13) (Levkowitz.H. 1997. p.6 J. cf. chroma. vriluc

Infrarcd light: Abbreviated as IR. Ranges from 700 (or SOO) nrn to 1 mm in the electrornagnt.tic radiation spcctrum. Near-IR: 800 nm -2.5 pn, mid-IR: 2-5-50 pn. far-IR: 50 pm - 1 mm. IR is invisiblc and has Iongsr wavelengths. lowzr frequencies. and less encrgy than visible light (Ag0ston.G.A. 1987) (McDoire1l.R.S. 1997) (Skoog.D.A., et al. 19%). cf. ultrriviole[ light

IR: Infirirsd light.

ISO: The International Standards Organization (Fel1er.R.L. 1985. p.41).

Lake pigment: Pigment made by dyeing incrt coiourless particles. The dyestuff is prrcipitated on the particles that serves as a substrate o r as a carrier of the dye t Colour Iticfcr 3rd sd. 19S2. pp.6-9) (Gettens.R.J.. et al. 1966. p.96).

Langlcy: A unit for light energy. 1 Langley = 1 caI/crn2 = 4.1 S-4 ~/crn ' = 3 1840 ~/m' ( U T C C Tesr iCZerlzod 16- 1990). cal: calorie. I: Joule.

Light dosage: The total energy imdicited as light over a dssignated period of rime. Expressed 3s the light intensity multiplied by the tims period. with the unit "l.~x hour" (&O "lx-hr"). cf. light intensity. UV dosage

Lightfristntss: StribiIity of colour agriinst light darnage. The propeny of a material of being resistrint to coiour deterioration caused by light (Ba1lard.M.W. 1985) (Fellsr,R.L. 1985) ( Fe1ler.R.L.. et al. 1978) (Fel1er.R.L.. et al, 1979 ). cf. fugitive

Light intcnsity: The brightness o f illumination expresscd in a numerical ilgure. AIso called '~illurnination" o r "illuminance." Expressed by the unit "lux" (rilso "lx"). 1 lux = 1 lumen / rn2. (Mac1eod.K.J. 1975. p.7). cf. light dosage. UV content

Lightness: AIso callsd brightness. Iightness. merric lighmsss. luminance factor or value (Ag0ston.G.A. 19S7. p.l-4) (Levkowitz.H. 1997. p.7). The incrcase in lightnsss does not always imply that the colour becornes more whitish.

Lightness function: Lightness of the colour of an objrct undsr a specific illumination. and is calculatsd using the CIE L*a*b* colour specification (Agoston.G.A. 19S7. pp. 107.24 1).

Lightening: A phenornenon of colour deteriorrition in which lightness increases. saturation decrcases and the colour becomrs more whitish (Ellis,M.H., et al. ( 1) 1999). cf. fading. darkcning, yellowing

Luminance: Lightness of illumination. rspecially in the CIE colour systems (Agost0n.G.A. 1987. pp. 13. 54).

Luminance factor: Lightness of the colour of an object undsr ri specific illumination in the CIE colour systems (Agoston.G.A. 1957. pp.55.245).

Luminescence : Re-emission of electromrignctic energy frorn a substance following energy absorprion. Luminescence can be fluorescence or phosphorescence (Vocdisch,R. W. Pign~etir Hmdhook v. 1. 1973. pp.89 1-893). cf. re flectance. fluorescence. phosphorescence

Luminescent: Having an ability to re-ernit the absorbed energy a s luminescence. A luminescent substance can be cither fluorescent o r phosphorescent (Voedisch.R.W. Pignretzr Ffarui6ook v . 1. 1973. pp.89 1-892). cf. fluorescent, phosphorescent

Lux: Sec "Light intensity."

Mttric lightness: Lightness of a colour of an object in the CIE L4a*b* colour spccification. AIso çailcd the (CIE 1976) liehtness function (Agost0n.G.A. 1987. pp. 107. 23 1).

hlcdium: .4 material in which a pigment is suspendcd so that the pigment crin be npplicd to ri surface (Mc~rericrls cmd Teclirioiog~ (5 ) . p.3 17). The word medium is used in more generril terms than the ivad "vehicle."

hfil: .A unit for thickness. 1 mil = 1 x 1 0 ' ~ in = 0.023 mm. Imm = 30 mils ( [ mil is one thousandth of an inch.).

North tvindow light: Daylight. Indirect sunlight thrit illuminates a roorn through a nonh-facing \vindo\v. Preferred by an conservators as an illumination source for colour matching and inpainting.

Non-fluorescent: Not having an ability to tluorescing o r ro glowing under designritcd conditions. When talking about tine arts or colours. non-fluorescent rneans thai the material does not slow in daylight nos undcr ultraviolet light. nor is it phosphorescent.

OBA : Fluorescent brightener-

Opacifier: An opaque material thrit is mixed in a transparent material to make the mixture to appsar opaque.

Optical brightener: Fluorescent brightener.

Optical brightening agent: Fluorescent brightener.

Paint: A pigment suspension in a solution wirh si film-forming resin. Ofren contains solvent. bulk material. stabilizers and other additives (Muterinls arid Tecltriciogy (5). p.3 17). Gives colour to a surface by formin2 3 pigrnented fiIm coating. cf- dyr:

Phosphor: A luminescent substance (Vosdisch,R.W. Pigwmr Hnndbook v.1. 1973. p.907).

Phosphorescence: Re-ernission of electromagneiic energy from a substance following energy absorption. or luminescence that continues after the exciter is removed. Phosphorescence continues longer than fluorescence but it is not always long enough to be rccognised by human eye (Voedisch.R.W. Pigrnerit HnrzciDook v . 1. 1973. pp.89 1-89?) (Weik.M.H. 1997). cf. reflsctance, fluorescence, luminescence

Phosphorescent: Hriving an ability to re-ernit the absorbed energy as phosphorescence or alierglow (Voedisch,R.W. Pigrrterrr Ha~idbook v. 1. 1973. pp.891-892) (Weik.M.H, 1997). cf. fluorescent. luminescent

Pigment: A colorant, o r a material to give a colour to another material, in the fonn of insoluble solid panicles (Co/orcr Ittdex 3rd ed. 1982. pp.6-9). Pigment needs to be suspendcd in (mixed with) the vehicle or solvent with a film-forming resin and then applied on a surface as a coating.

Plastic: Material consisting of one or more kinds of high polymer a s essential components, can bc shaped by f7ow in the rnanufacturing prcxess. and is solid in its finished state. Excludes nibbers. textiles, adhesives and paints. The terms polyrner. resin and plastic(s) might bc interchangeable but polyrncr and resin often denote basic materiais whereas plastic(s) encompasses compounds containing additives such as plasficisers ( IVhittirtgrori 's Dicriotaary of Plcrsfics, 1993).

Purity of colour: Excitation purity (Agoston.G.A. 1987. pp.58-6 1 ).

Quenching: Quznching is an elimination of fluorescence due to absorption of the emitted light by other molecules. due to molecular collisions. and dur to othcr processes. The optimum fluorescence efficicncy of dye is gained by minirnising qucnching in a ditutc solution or in ri solid form (Manindil1.hl.G. 19SS. p. ISS) (Voedisch.R.W, Pigtnetu Hatidbook v . 1. 1973. pS93) .

Relative humidity: Cornmonly caIled hurnidity and expressrd in percentage. The ratio o f a mscisured amount of water vapour in the air against the maximum amount of writcr vapour that the air crin contain (saturation point) at that temperature (Cassar.M. 1995. p. 147). cf. absolute humidity

Resin: Resin defined by ASTM D883 is "a solid o r pseudosolid matcrial, often of high molecular weight. that exhibits a tendency to tlow whcn subjected to stress. usually hris a softening o r melting range. and usually fractures conchoidrilly" (Resin. Il'lrirririgrott 's Dicrionnry of Plastics. 1993. p.42S). In a broad sense. the tcrm resin designates ciny polymer that is a basic matsrial for plastics but the definition differs rimons industries (Resin. Wrirtirtgto~t 's Dicrio~iciq of Plasrics. 1993. p.428). Naturd resins are transparent o r trrinslucent organic substances that are enuded by plants. and are solid o r semi-solid, rimorphous and fusible. Natural resins are soluble in organic solvents but not in water. They are also called varnish resins. Examples of natunl resins art: copal, amber. and Canada baisam (C1rissJ.B. 1997. pp.29 1-292) (Resin, Natural. Wzittirigrori 's Dicriotzary of Plastics. 1993. p.428).

RH: Relative humidity.

Saturation: Purity of colour. Excitation purity. Chroma in the Munsell Color Systern. A saturatrd colour is vivid and bright rather than pastel (Agoston.G.A. 1987. p. 13) (Levkowitz.H. 1997. p.7).

Size: Adhesive added to paper during i t s rnanufacturing process to improve coherence among cellulose tïbres, and to improve the surface properties so thrit the product has appropriate strength, good printability. ease of uriting. cornfortable handling propenies and an enhanced appearance. To treat priper with a sizing agent. (Burns,T. 1999) Crinvases for painting and other textiies rire also sized.

Spectrophotometer: An instrurnrnt rhat compares two bsrims of light and determines the intensity ~f specirnen light against the reference light as a function of wavelength o r frequency (Skoog.D.A., et al. 1998: p. l S2).

Specular reflection: Reflection frorn a smooth surface such ris a rnirror that gives a clerir. sharp image of the lighr source. Specular reflection is observed at the sarne ansle with the incident light o n the opposite sidc of the line perpendicular to the refiecting surface (Weik.M.H. 1997) (Robemon.A.R. 1986. p. 133).

Substantivity: The ability of a pctper dye io be absorbed by ceIlulose fibres from an aqueous medium (Murray.S.G. 1996. p. 178).

Thcrrnoplastic resin: A critegory of organic polymer that is a hard solid at lower temperature, is soft at higher temperature, and accepts repeated heating and cooling within a certain range of temperature without 3 change in the rnolecular structure (IVhirrirtgrorz 's Dictionun of Plrrsrics. 1993). cf. thermosettint resin

Thermosetting resin: A category of organic polymer that becomcs hrird by hertting, critalysis or other chernical reactions. Once cured (hrirdcncd). it dors not becorne soft by hheating again (\VI~irritlgrorl's Dicrionary of Plastics. 1993). cf. thcrmosctting resin

Tint: The coIour produced by rnixing a colorrint and a white o r transparent material.

Toncr: This word has two dcfinitions: a "full strength pigment" that is not mixcd with other rnateririls. or a '.concentraied colouring matter" that is precipitated frorn a dye solution in water (Coloiw Itidrr 3rd ed. 1982. p.6).

Ultraviolet light: Abbrevirtted as UV. Ranges from 1 0 nrn to 300 nm in the electromagnetic radiation spectrurn. Near-UV: 200400 nm. vacuum UV: 10-200 nrn, UV componcnt in daylight: 300-400nm. UV is invisible and has shoner wavelcn_eths. higher frequencies. and more enrirgy than visible light ( .4p~i0n.G.A. 1957. pp. 17. 19) (McDowell,R. 1997. p.630) (5ngh.N. 1999. p.3S) (Skoog.D.A.. et al. 199s. pp. 1 19. 146). cf. Infrared light

Unsaturated: Means chat the çolour is pastel. dull o r wesk.

UV : Ultraviolet light.

UV absorber, UV stabiliser: Additive in varnish to protzçt 3 paint layer from ultraviolet Iight. Radical scavensers such as Tinuvin 292 (Ciba-Geigy) are called hzdered amine ligltr srabiliscrs (HALS). UV absorbers rire substituted 2-hydroxybenzophcnones such as Univil 300.397 and 490 (BASF) and substirutsd 2-hydroxybenzotriazoles such as Tinuvin 327 and 328 (Ciba-Geigy). (Bourdeau J. 199s. pp.2 1 1-220).

UV content: T h e ratio o f UV energy in the total energy o f Iight k i n g irradiated at the moment. UV content is called "UV component" by museurn professionals. Expressed with the unit "micro watts per lumen" (rilso "pW / lumen"). cf. light intensity, UV dosage

UV dosage: T h e total energy irradiated as UV over the designated period of time. When the UV content is constant. the UV dosage is expressed as the UV content rnultiplied both by the light intensity and by the timc psriod. with the unit "(micro) watts hour" (also "(p)W hr"). cf. light dosage. UV content

UV filter: A material that cransrnits visible light but not ultraviolet light. Used as a transparent coating on windows. illumination lamps. painting frames. and glass show cases in museurns. galleries. and a n conservation laboratories.

UV fluoresccnt: Being capable o f fluorescing o r glow upon receiving ultraviolet Iight. cf. daylight tluoresccnt

Value: Lightness of colour in the Munsell Coior System (Agoston.G.A. 1957. pp. 14-16. 1 16) (Lcvkowitz.H. 1997. p.7). Also csl lrd brightness, lightness, metric lightness, luminance factor. (t4goston.G.A. 1987. pp.53-55, 107,241) (Levkowitz.H. 1997. p.7). T h e increase in value does not impiy thrtt the coIour bçcomes more whitish. cf. chroma. hue

Varnish: A transparent hard glossy coating of film-formine resin applied ovcr a paint layer (hIuterials ntid Tecl~rrolog_v (5). p.3 17). Varnish protects paint Iayer frorn dust, soifing, air pollutant. and scratching. Varnish containing UV absorber o r UV inhibitor protects paint layer from ultraviolet light. as well. Vrirnish rnay contain a small amount o f pigment for a coloured effect.

Vehicle: A material in which a pigment is suspended so chat the pigment can be applied to a surface (V0cdisch.R. W. Pigrrient Handbook v.2. 1973). Medium.

Visible light: Visible light is a pan of the clectromagnetic spectrum that crin be sesn by the hurnan cye. and its wavelength ranges approximately frorn 400 nm to 700 nrn (Agoston.G.A. L9S7. pp. 17. 19) (McDowe1l.R. 1997. p.630) (Skoog,D.A., et al. 1998. pp.119. 146).

Wavelength of Iightkolour: The distance the electrornagnetic radiation (light) proceeds during one cycle o f vibration. Wavelength is rcciprocal of frequency. The unit for wavelength can be nrn (nano meter) o r km (Skoog.D.A.. e t al. 1998). cf. frcquency

Yellowing: A phenornenon o f colour deterioration in which ri yellowish hue is griined. Yrllowing is often mrntioned in ri discussion on clerir. transparent, white. or lightly coloured materials such ris vrirnish. rtdhesive, resin and priper. cf. drirkening. fading. li_ghtening