carty nceca 2012

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The Effect of Firing Time on Glaze Chemistry (Deciphering Ancient Practice Through Forensic Analysis) William M. Carty Kazuo Inamori School of Engineering Alfred University NCECA · 2012 Seattle, Washington Hyojin Lee Alfred University

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Page 1: Carty Nceca 2012

The Effect of Firing Time on Glaze

Chemistry(Deciphering Ancient Practice Through Forensic Analysis)

William M. Carty Kazuo Inamori School of Engineering

Alfred University

NCECA · 2012

Seattle, Washington

William M. Carty

Hyojin Lee Alfred University

Page 2: Carty Nceca 2012

Background

Glaze-body interaction is extensive during firing.

This results in a significant shift in the glaze

chemistry that increases with firing time.

Modern bodies average 60 µm penetration depth

(the thickness of a typical human hair).

The analysis of a 12th Century Korean Celadon,

from the Koryǒ period (918-1392 CE), indicated

approximately 200 µm penetration depth!

This was significantly greater than anything we

had evaluated up to that point.

Page 3: Carty Nceca 2012

Examples: Time-Temperature Results12th Century Bowl

Koryǒ period

(918-1392 CE)

Gangjin, Korea Gimjae, Korea

4 days at 1180°C

3 days at 1210°C

4 days at 1050°C

Page 4: Carty Nceca 2012

Analysis of Ancient Shards

This analysis can be tricky:

Shards from kiln sites may not have been

properly fired (discarded as inferior).

How to identify the original body-glaze interface How to identify the original body-glaze interface

(when the glaze was applied)?

The sample will likely be destroyed.

Page 5: Carty Nceca 2012

Analytical Tool: WDS

Wavelength Dispersive Spectroscopy (WDS), an electron

microscopy tool, allows us to map chemistry.

By comparing chemistry maps, we can identify chemistry locations and

ultimately chemistry shifts.

There is (essentially) no Ca in the

Gla

zeThere is (essentially) no Ca in the

body, therefore all Ca comes

from the glaze.

Need the original body-glaze

interface (as applied).

Ca MapBo

dy

Gla

ze

Ca Map

Page 6: Carty Nceca 2012

Example from a modern body

Alumina in the body served as a marker.David Finkelnburg, M.S., Alfred University, 2006

Page 7: Carty Nceca 2012

Zircon used as a marker in

experimental studies

Map of Zr Map of Ca

Original Body-Glaze

Glaze

1300°C · 1 hour

Original Body-Glaze

Interface

Body

Zircon is typically not soluble in either the body or glaze.

It was added to the body to provide a marker.

Glaze penetration occurs around the zircon particles.

Page 8: Carty Nceca 2012

Results of experimental studies

1300°C

1 hour

10 hours

1 week

Thomas Rein, B.S., Alfred University, 2010

Page 9: Carty Nceca 2012

Gimjae Shard Sample

Penetration Depth:

∼100 µm

Page 10: Carty Nceca 2012

Gangjin Shard Sample

Penetration Depth:

∼170 µm

Page 11: Carty Nceca 2012

12th Century

Koryó Period Bowl

Mullite (from grog) now serves as the marker.How to identify the original body-glaze interface?

Penetration Depth: ∼200 µm

Page 12: Carty Nceca 2012

Greater penetration of the glaze into the

body means a greater shift in chemistry

Glaze

chipped from

the body is far

from the from the

original glaze

chemistry

This example

assumes that the

penetration depth is

equal to the

application thickness

Page 13: Carty Nceca 2012

Chemistries of Korean Celadon

Bodies and Glazes

SiO2 Al2O3 TiO2 Fe2O3 Na2O K2O MgO CaO

Glazes

57.6 12.4 0.1 2.1 0.7 2.8 4.2 17.7

58.1 13.9 0.2 1.4 0.5 2.9 1.8 19.9

59.6 14.1 0.1 1.4 0.8 3.8 2.7 16.0

BodiesWe

igh

t %

Bodies

76.0 17.0 0.8 2.1 0.7 2.5 0.5 0.3

73.0 17.5 0.9 2.8 0.8 2.6 0.7 0.2

73.0 18.0 1.2 2.5 0.9 3.4 0.5 0.5

Nigel Wood, Chinese Glazes, 1999

Glaze

2.24 0.31 0.00 0.05 0.02 0.08 0.16 0.73

Body

19.8 2.7 0.19 0.49 0.21 0.48 0.23 0.09

UM

FW

eig

ht

%

Page 14: Carty Nceca 2012

Comparison with modern ceramics?

Modern bodies: 60 µm penetration depth.

Ancient bodies: 200 µm penetration depth.

How to rectify?

Ancient bodies must have been held at

temperature for significantly longer times. temperature for significantly longer times.

Body analysis indicates much lower firing

temperatures.

We need a new matrices.One for firing temperature &

one for glaze penetration depth

Page 15: Carty Nceca 2012

Sili

ca

UM

F in

Gla

ss P

ha

se

14

16

1300°C

Body glass chemistry at different temperatures

Korean Celadon body

Firing Time (hours)

100 101 102

Sili

ca

UM

F in

Gla

ss P

ha

se

8

10

12

1200°C

1250°C

1300°C

Furnace Setting

1200°C

1250°C

Page 16: Carty Nceca 2012

Penetration depth at different temperaturesG

laze P

enetr

ation D

epth

(µm

)

103

1200°C

1250°C

1300°C

Korean Celadon body and glaze – estimated chemistries

Firing Time (hours)

100 101 102

Gla

ze P

enetr

ation D

epth

(

101

102

Page 17: Carty Nceca 2012

Firing conditions for Korean Celadons?

SampleSilica

UMF

Glaze

Depth

(µm)

Firing time

(hours)

Firing

Temperature (°C)

12th Century

Koryó bowl11.8 190 100 1180

Koryó bowl

Gangjin Shard 11.1 170 70 1210

Gimjae Shard 7.5 100 100 1050*

* Data and sample condition (poor strength, continuous

porosity) indicates this shard was underfired.

Page 18: Carty Nceca 2012

Correcting glaze chemistry to reflect

glaze-body interaction

Used a “rule of mixture” (ROM) approach.

dG,f × ChemG,f = dB × ChemB + dG,A × ChemG,A

d ≡ final glaze thickness.dG,f ≡ final glaze thickness.

dB ≡ depth of body penetration.

dG,A ≡ Original glaze application thickness.

ChemG,f ≡ Fired glaze chemistry.

ChemB ≡ Chemistry of the body.

ChemG,A ≡ Chemistry of glaze as applied.

Page 19: Carty Nceca 2012

Original Glaze Chemistry (as applied)

SiO2 Al2O3 Fe2O3 Na2O K2O MgO CaO

35.6% 7.5% 0.4% 0.5% 3.8% 6.8% 46.7%

Seger

0.564 0.070 0.002 0.007 0.039 0.160 0.794

Final Glaze chemistry if Final Glaze chemistry if

the glaze batch is

calculated to match the

fired glaze chemistry

(ignoring the body

incorporation).

Page 20: Carty Nceca 2012

Glaze chemistry for modern firing

Calculated glaze

SiO2 Al2O3 Fe2O3 Na2O K2O MgO CaO

52.3% 11.8% 1.3% 0.6% 3.4% 4.1% 26.7%

Seger

1.393 0.186 0.013 0.016 0.058 0.163 0.764

Calculated glaze

batch chemistry for a

modern glaze to

match ancient glaze

(corrected for modern

firing cycles and

incorporating body

interaction).

Page 21: Carty Nceca 2012

Proposed batch for ancient celadon

and modern equivalent (1250°C)

G-200 EPK Whiting Flint

Koryǒ Celadon

(100 hour soak)19.9 4.1 67.5 8.5

(100 hour soak)

Modern

(3 hour soak)21.9 14.5 44.9 18.7

Similar feldspar, but a significant increase in clay and silica (due to

the reduction in glaze-body interactions as

a consequence of much shorter firing times).

Also, much less whiting.

Page 22: Carty Nceca 2012

Conclusions

Glaze-body interactions significantly alter the glaze

chemistry during firing.

Compensating for body-glaze interactions leads to a

very different glaze batch compared to

the batch calculated from a glaze chip.

very different glaze batch compared to

the batch calculated from a glaze chip.

Knowing the extent of the glaze-body interactions is

essential to formulate glazes

for modern firing schedules that mimic

ancient results.

Page 23: Carty Nceca 2012

Acknowledgements

Korean Institute of Ceramic Engineering and Technology (KICET), Korea

David Finkelnburg (M.S., 2006)David Finkelnburg (M.S., 2006)

Tom Rein (B.S. Thesis, 2010)

Chorwon Kim

Matt Katz

Hyojin Lee (my co-author)