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Journal of Cultural Heritage 9 (2008) 179e183http://france.elsevier.com/direct/CULHER/

Case study

Physico-chemical and analytical studies of the muralpaintings at Kariye Museum of Istanbul

Sara Bianchin a, Umberto Casellato a, Monica Favaro a, Pietro Alessandro Vigato a,*,Maria Perla Colombini b, Gwanelle Gautier b

a ICIS e CNR, Corso Stati Uniti 4, 35127 Padova, Italyb Dipartimento di Chimica e Chimica Industriale, Universita di Pisa, via Risorgimento 35, 56126 Pisa, Italy

Received 20 February 2007; accepted 25 October 2007

Abstract

Optical (OM) and Scanning Electron Microscopy (SEM-EDS), mFT-IR spectroscopy and Gas Chromatography-Mass Spectrometry (GC-MS)have been used to ascertain, at molecular, nano- or micrometric level, the state of conservation of the mural paintings at the Kariye Museum inIstanbul. The characterization of the original organic and inorganic materials used in the painting preparation and plaster layers allows to definethe painting techniques. Furthermore, the nature and the extent of the degradation phenomena and the materials used in subsequent restorationshave been identified. The poor state of conservation of the pictorial cycle, due to quite severe deterioration processes, noticeable detachments,presence of salts, etc., strongly calls for a prompt intervention, guided by an exhaustive and appropriate scientific approach.

The present study offered the possibility to compare the results obtained by different techniques on the same samples, in order to evaluateperformance, advantages, limits of each of them.� 2008 Published by Elsevier Masson SAS.

Keywords: Mural painting; State of conservation; Pigments; Inorganic materials; Binders; Pictorial technique

1. Research aim

This study represents a contribution to an integrated inves-tigation aimed at an exhaustive description of the differentmaterial typologies present in the building. Physico-chemicaland analytical studies of pictorial fragments, collected fromdifferent areas of the wall paintings, were especially addressedtoward the determination of the stratigraphy and the character-ization of the original composition and the restoration mate-rials, in order to define the state of conservation and thepictorial technique. The study of salt formation and their effecton the mural paintings, the degradation products of organicand inorganic compounds and the comparison of the resultsobtained by different techniques on the same sample representother valuable goals of this research.

* Corresponding author. Tel.: þ39 049 829 5962; fax: þ39 049 870 2911.

E-mail address: vigato@icis.cnr.it (P.A. Vigato).

1296-2074/$ - see front matter � 2008 Published by Elsevier Masson SAS.

doi:10.1016/j.culher.2007.10.004

2. Introduction

Prior to the Turkish conquest of Constantinople in 1453 andthe subsequent conversion of many of the city’s Byzantinechurches to Moslem use, the Kariye mosque was the churchof the celebrated monastery of Chora. The existing superstruc-ture of the church is not of great antiquity but incorporatesthree major phases of Byzantine construction of the XI, XII,and XIV centuries [1].

The excavations carried out during the restorations haveshown that a new church was erected during the Comnene pe-riod, in the late XI century, on a site within the grounds of theancient monastery which had not been occupied by any of theearlier churches. They have shown that this church was partlydestroyed and was re-erected, although this rebuilding is notrecorded in any of the extant documents. Finally, in the seconddecade of the XIV century, extensive restorations were carriedout and new additions were made [1] (Fig. 1).

Fig. 1. Plan of S. Saviour in Chora, today Kariye Museum (a). The rooms L, M, N, O, U and P form the Parecclession. The Naos is connected to the south with

Parecclession. The rooms A, B, C, D, E, F and G, H, I, J, K form the Narthexes. A view of particular of the pictorial cycle (b).

180 S. Bianchin et al. / Journal of Cultural Heritage 9 (2008) 179e183

The Narthexes and the Parecclession were an entirely newconstruction of the ktetor (curator) Theodore Metochites; andstudies made by the Byzantine Institute [1] indicated that theParecclession was the mortuary chapel of the monastery. Firsta monastic church, then a mosque, the Kariye building is nowone of the museums of Istanbul. During these modifications itsfrescoes and mosaics suffered from extensive whitewashing,and in 1948 they were heavily restored [1]. Currently, theyneed a careful check up and quite probably a new intervention.

3. Experimental

Twenty-one samples containing different polychromieshave been collected from the Parecclession and Narthex.The fragments were first observed as received, then their strati-graphic sequence was investigated on cross-sections by opticalmicroscopy analyses with an Olympus BX51 microscope un-der visible light and UV illumination, the latter to make outthe organic layers. The cross sections were analysed also bySEM-EDS, with a Philips XL-40 instrument equipped withan energy dispersion microanalytical system (EDAX-EDS)[2], after metallization by electro-deposition of a graphitefilm. mFT-IR analyses were primarily carried out on the sam-ples crushed on a gold surface to study especially the bindingmedia of the painting layers. Extraction experiments with dif-ferent solvents (dichloromethane CH2Cl2, water H2O, ethanolEtOH, acetone), followed by deposition of some drops of theextracted fraction on a gold surface, were carried out to studyand identify the organic components. The infrared analysiswere carried out by a Nicolet Magna IR560 FT-IR Spectrom-eter and Spectra Teck microscope [3]. The IRUG database [4]was used for the identification of the material constituents ofthe samples.

Samples suitable for GC-MS measurements were preparedaccording to the procedure described elsewhere [5]. Wheneveran interference from pigments was suspected, a clean up of theammonia extract by OMIX tips (Varian, Milan, Italy) wasperformed [6]. A 6890N gas chromatograph (Hewlett Packard,Milan, Italy), equipped with a PTV injection port and a mass

spectrometric detector mod. 5975 (electron impact 70 eV, ionsource temperature 180 �C, interface temperature 280 �C) wasused. Chromatographic separation was performed with a chem-ically bonded fused-silica capillary column HP-5MS (AgilentTechnologies, Palo Alto, CA, USA). Chromatograms were re-corded both in TIC (Total Ion Current, mass range 50e600)and SIM (Single Ion Monitoring) mode.

4. Results and discussion

Twenty pictorial fragments and one specimen of surfacematerial, representative of the pigments and the other inorganicor organic products employed in the pictorial cycle or in thesubsequent restorations, were sampled from appropriate areasof the Parecclession and the Narthexes rooms (Table 1). Thestratigraphic sequence, studied by optical microscopy and bySEM-EDS, gave a satisfactory indication of the differentcomponents inside each layer. As an example of the complex-ity of the structure, the stratigraphic sequence of KM58 isreported in Fig. 2. Finally, mFT-IR studies, primarily addressedto corroborate the optical and electron microscopy data, of-fered a fast and relatively easy characterization of the inorganicand organic compounds. Subsequent GC-MS measurementsallow a more reliable identification of the organic products.

The inner layer of all the samples mainly contains a whitishcalcite matrix with variously sized and coloured inclusions ofsand aggregates. A thin layer containing calcite with a finegranulometry, identified on several samples (KM8, KM9,KM10, KM11, KM18, KM22, KM46), may be attributed toan intentional finishing applied to smooth the surface beforethe applications of the pigments. Four samples (KM25,KM30, KM46, KM61) can be considered as made of stucco,as the plaster is mainly constituted by gypsum (calcium sulfatedihydrate, CaSO4 $ 2H2O). Mineral and synthetic inorganicpigments have been identified on the different painting layers:green earth (potassium and iron silicate, K[(Al,FeIII),(FeII,Mg)] (AlSi3,Si4) O10 (OH)2, on the basis of SEM-EDS andIR spectroscopy), carbon black, natural and artificial lapisla-zuli [(Na, Ca)8 (AlSiO4)6 (SO4, S, Cl)2], red (Fe2O3) and

Table 1

Description of the fragments detached from Parecclession and Exonarthex rooms

Label Description

KM8 Sample from the green basement on a black background of the third left pilaster

KM9 Black sample from the lower part of the first figure of the Saint on the left with the inscription Kypmao of the apsidal basin

KM10 Yellow sample of the lower part of the third figure from the left above a false marble of the apsidal basin

KM11 Yellow fragment from the figure on the right, detached 160 cm from the ground

KM14 Blue sample from the Virgin Mary with the Child of the right wall

KM18 Red sample from the edge of the triumph arch

KM22 Blue sample from the left figure on the right of the window opening first lunette on the left above a marble structural component

KM25 Gilding sample from the marble bas-relief on the left of Parecclession

KM29 Blue sample from the top area of the mant of the Virgin Mary with the Child in the Parecclession room

KM30 Gilding sample containing a blue pigment from the marble bas-relief

KM31 Sample from the red garment of the third figure in the Parecclession room

KM33 Sample from the green mantle on the right wall, first niche under-arch of the Parecclession room

KM34 Yellow sample from the right wall, second niche under-arch on the right of the Parecclession room

KM36 Red sample from the garment of the first figure on the right wall of the Parecclession room

KM37 White sample from the frame of the first figure on the right wall

KM42 Red sample from the stock of the fifth figure on the right wall

KM46 Gilding sample containing polychrome pigments from the left side of the altar

KM56 Green sample from the right wall, entrance arch on the cornice of the Parecclession room

KM58 Red sample from the right wall, triumphal arch of the Parecclession room

KM61 Sample from an area containing different pigments which separates the vertical wall of the apse from the orange marble frame in the apse

181S. Bianchin et al. / Journal of Cultural Heritage 9 (2008) 179e183

yellow (FeO(OH)) ochres, minium (Pb3O4), barite (BaSO4),gold powder and leaf for gilding, azurite (2Cu-CO3 $ Cu(OH)2), antimony white (Sb2O3), basic lead carbon-ate [2PbCO3 $ Pb(OH)2] and traces of bone white [Ca3(PO4)2][7e10]. In KM29 the surface percentage of barium and tita-nium, too high to be related to the employed the earths respon-sible for the yellowish colouration of the sample, is certainlydue to an intervention during the last century, dating after1920, when titanium oxide was produced for the first time[8], although largely used only from the mid 1930s. The pres-ence in KM46 at same time of titanium oxide with traces ofbarium sulfate (BaSO4) [9], a pigment employed since 1774,offers a convincing indication of restoration interventionsand may be useful as qualitative dating marker.

All the samples have a non-homogeneous surface layer ofgypsum with traces of Fe and Si, possibly due to a heavy

Fig. 2. The cross-section of KM58, observed by MOP (white lamp, 100X): a)

calcium carbonate, b) red ochre and whitewash, c) red ochre and carbon black,

d) neoformation gypsum.

repainting although an environmental pollution by S-contain-ing contaminants cannot be ruled out. Furthermore, sodiumand/or calcium oxalate and sodium chloride, identified bySEM-EDS and IR spectroscopy, quite often occur.

According to OM and SEM-EDS indications, in blue areas(KM14, KM22, KM29) a grey preparation layer is appliedabove the plaster, and is composed by small black inclusionsof whitewash [7,10] and vegetable carbon black [7] (Fig. 3).

The thickness (5e35 mm) of the layers and the presence ofproteic binders in KM8, KM9, KM14, KM18, KM22, KM29,KM31, KM37 and KM61 (IR bands at 3400e3200 cm�1

n NH, n C]O band at 1650 cm�1, d CeNeH band between1565 and 1500 cm�1), the latter corroborated by GC-MS, indi-cate the use of tempera. In two samples bees wax was identified(KM11, KM22 IR bands between 3000 and 3200 cm�1 n OH, at2924 and 2854 cm�1 n CH of the aliphatic groups, at 1740 cm�1

n C]O of ester groups and at 1480 O 1300 cm�1 d CH of thealiphatic groups, at 1300 O 900 cm�1 n CO) [7,10].

mFT-IR investigations probably indicate the use of a lake[11] in KM30. Lake pigments are quite complex materials,very difficult to be correctly identified by IR: the spectrum ofthe extracted fraction (bands at 1736 and 1635 cm�1 n C]Oof ester groups, at 1187, 1145, 1093, 1026 cm�1n CeO) paral-lels that of shellac [12], a natural resin used as coating andadhesive. However the typical OM autofluorescence of shellacunder UV examination, was not particularly clear.

Poly(vinyl acetate) [11] (n C]O at 1739 cm�1 of carbox-ylate esters and n CeO at 1258, 1240, 1087 and 1024 cm�1),a synthetic polymer in the artists’ market as medium since1938 and as adhesive for gilding [11] was identified inKM61, KM25 and KM30: it strongly supports a recent resto-ration intervention.

IR spectrum of the CH2Cl2 soluble fraction of KM34 andKM42 proves the use of the artificial cellulose nitrate [11](n OH bands at 3503 cm�1, n C]O at 1729 and 1653 cm�1

Fig. 3. Cross-section of KM14 (50�) (a), KM22 (50�) (b), KM29 (200�) (c).

KM29

KM9

KM8KM22

KM61

KM37

KM14

KM18

KM30

-4

0

-3 -2 -1 0 1 2 3 4 5 6 7 8PC1

PC2

egg

casein

animal glue

Fig. 4. Score plot of the Principal Component Analysis of the examined

samples.

182 S. Bianchin et al. / Journal of Cultural Heritage 9 (2008) 179e183

of ester groups and n CeO at 1285, 1240, 1121, 1072 cm�1),a polymeric material used as consolidant since the end of theXIX century and for the whole XX century particularly duringthe fifties. This ascertains that the fragment belongs to a re-touching of the last century (approximately 1930e1950,when the last restoration was carried out).

The use of natural lapis lazuli in KM14 and KM22 and ar-tificial lapis lazuli [7,10,11,13] in KM29 was proved by an in-frared ‘‘marker’’: the occurrence of a well detectable band at2341 cm�1, in fact, is a proof of the use of natural lapis lazuli[12]. In addition a shape difference of the grains of samplesKM14 and KM22 containing natural lapis lazuli and KM29with artificial lapis lazuli adds additional information for dis-criminating between the two lapis lazuli typologies. The pres-ence of azurite [7,10,11] was ascertained in KM30 (bands at1490, 1415, 1090, 837 and 817 cm�1). Furthermore, the IRspectra prove the presence of carbonates, gypsum, oxalatessalts and silicates in all the detached samples. GC-MS studiestestify the occurrence of oxalate and sulfate salts.

Samples KM8, KM9, KM11, KM14, KM18, KM22, KM25,KM29, KM30, KM37, KM46 and KM61 were analysed usingthe combined analytical procedure based on multiple extrac-tions and GC/MS analysis described in the literature [5] forthe protein and lipid characterisation.

The Fig. 4 reports the score plot of the Principal ComponentAnalysis for all the examined samples and the reference ones.On this base and on the proteinaceous profiles, it results thatKM11 is outside of the clusters because the proteinaceous ma-terial determined is at the blank level, anyway, traces of hy-droxyproline may indicate a quite low level of animal glue;KM8, KM9, KM14, KM22, KM29, KM30, KM37 containa mixture of glue and casein in different ratios; KM61 mainlycontains glue and probably another proteinaceous matter suchas whole egg or yolk as the lipid analysis revealed traces ofcholesterol; KM18 may contains glue and another proteina-ceous material, probably egg though no cholesterol was high-lighted in the lipid analysis. GC/MS analysis rules out thepresence of drying oils and plant resins and evidences tracesof animal fat probably deriving from impurities in the protein-aceous material.

Table 2 summarises the organic materials in the samplesidentified by GC/MS and mFT-IR. A comparison of the ob-tained data clearly indicates that the different physico-chemicaland analytical methodologies are complementary each other,

jointly giving an exhaustive knowledge of the organic andinorganic materials in this pictorial cycle and their evolutionin consequence of degradation processes and restorationintervention.

5. Conclusion

Integrated physico-chemical and analytical measurements,carried out on the same samples, allowed a satisfactorydescription of the components of the wall paintings and ofthe deterioration products together with those added duringsubsequent restoration interventions. The physico-chemicaldata offer quite convincing evidence about the pictorialtechnique used: fresco was mainly used but secco was alsoemployed with a tempera based on casein. The presence ofanimal glue may be related to its use for wetting the plasterbefore the application of tempera.

Mineral and synthetic inorganic pigments have been identi-fied: green earth, carbon black, natural and artificial lapisla-zuli, red and yellow ochres, minium, barite, titanium oxide,gold powder and leaf for gilding, azurite, antimonite white,basic lead carbonate and traces of bone white [7e10].

The presence of products, synthesized in more recent pe-riods of time (as cellulose nitrate, poly(vinyl acetate), bariumsulphate, titanium dioxide), clearly identifies areas involvedin past and/or recent restorations. On the other hand, a heavy in-tervention in the fifties of the last century it is well documented;

Table 2

Summary of the identified material in the samples

Sample GC/MS mFT-IR Pigments identified

Proteins analysis Lipids analysis

KM8 Glue þ casein e Proteins Green earth, white lime, carbon black

KM9 Glue þ casein e Proteins Carbon black, calcite

KM10 / / None Red ochre, white lime, carbon black

KM11 None Traces of animal fat None Yellow ochre, white lime

KM14 Glue þ casein e Proteins Lapis lazuli, white lime, carbon black

KM18 Glue þ egg e Proteins Red ochre, lime white

KM22 Glue þ casein e Proteins Lapis lazuli, white lime, carbon black,

traces of green and red earths

KM25 Glue þ casein Traces of animal fat Polysaccharide, PVA Gold leaf gilding, yellow ochre

KM29 Glue þ casein e Proteins Lapis lazuli, carbon black, lime white

KM30 Glue þ casein e PVA, proteins False gilding, yellow ochre, red ochre, azurite,

antimony white

KM31 / / Proteins Red ochre, white lime, carbon black, minium

KM33 / / None Green earth, lime white

KM34 / / Cellulose nitrate Yellow ochre, barite

KM36 / / None Red ochre, lime white

KM37 Glue þ casein e Proteins White lime, red ochre, carbon black

KM42 / / Cellulose nitrate Lime white, red ochre, carbon black

KM46 Glue þ casein e None Powder gold gilding, red ochre, yellow ochre,

azurite, white lime

KM56 / / None Green earth, white lime, carbon black

KM58 / / None White lime, red ochre, carbon black

KM61 Glue þ egg Traces of cholesterol

and animal fat

Proteins, PVA Yellow ochre, white lime, gold traces

e, the lipid content is at the field blank level.

183S. Bianchin et al. / Journal of Cultural Heritage 9 (2008) 179e183

it involved extensive areas of the pictorial cycle. Nevertheless,the physico-chemical data are able to give information on theoriginal materials used.

The scientific data indicate the pictorial cycle is in a criticalstate of conservation: several areas are affected by significantdecohesions and detachments of the pictorial layers, by thepresence of salts which deeply penetrated from the surfaceinto the bulk. For instance, NaCl was ascertained almost inall the investigated pictorial layers. Furthermore, the presenceof gypsum was proved in many samples.

This paper represents a first contribution to a wider inte-grated study aimed at an exhaustive molecular description ofthe state of conservation of the whole building. A further inves-tigation of the complexity of materials is currently in progress,particularly of mosaics, salts, mortars and building materials.

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