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Raman spectroscopy of the pigments on Korean traditional paintings
Accepted Manuscript Title: Raman spectroscopy of the pigments on Korean traditional paintings Author: Ji-Yeon Nam Kiok Han Jeong-Eun Ji Seung Kim Hanhyoung Lee Daiill Kang Minsu Han In-Sang Yang PII: DOI: Reference:
S0924-2031(16)30075-3 http://dx.doi.org/doi:10.1016/j.vibspec.2016.04.011 VIBSPE 2546
To appear in:
VIBSPE
Received date: Revised date: Accepted date:
13-10-2015 23-2-2016 20-4-2016
Please cite this article as: Ji-Yeon Nam, Kiok Han, Jeong-Eun Ji, Seung Kim, Hanhyoung Lee, Daiill Kang, Minsu Han, In-Sang Yang, Raman spectroscopy of the pigments on Korean traditional paintings, Vibrational Spectroscopy http://dx.doi.org/10.1016/j.vibspec.2016.04.011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Raman spectroscopy of the pigments on Korean traditional paintings
Ji-Yeon Nama, Kiok Hana, Jeong-Eun Jia, Seung Kima, Hanhyoung Leeb, Daiill Kangb, Minsu Hanc, In-Sang Yanga,*
a
Department of Physics and Division of Nano-Sciences, Ewha Womans University, Seoul
120-750, Korea b
Department of Conservation Science, Korea National University of Cultural Heritage,
Buyeo 323-812, Korea c
Conservation Science Division, National Research Institute of Cultural Heritage, Daejeon
341-22, Korea
*Corresponding author. Tel. +82-2-3277-2332, fax: +82-2-3277-2372; E-mail address: [email protected] (I.-S. Yang).
1
Highlights;
Raman spectroscopy of the pigments used in paintings of Korean heritage.
Identified some of the pigments on a Buddha painting of the Tongdosa temple, Korea.
Results would provide a useful scientific basis for the preservation of cultural heritages.
ABSTRACT Raman spectroscopy is now a well-established tool in characterizing archaeological materials, such as traditional paintings. In this report, we applied Raman spectroscopy to investigate the pigments used in Korean traditional paintings. Korean traditional colors are often represented by the five basic colors; blue, red, yellow, white, and black. In real paintings, the colors are more diverse including orange and green. We report a Raman spectroscopy of the various pigments found in Korean traditional paintings. Raman spectra are used to identify the several components of minerals in the pigments if they are mixtures of different minerals. Our work would provide a useful scientific basis for the conservation and restoration of aged and damaged Korean traditional heritages.
Keywords: Traditional pigments, Mineral pigments; Raman spectroscopy; Traditional painting; Nondestructive measurements; Vibrational spectroscopy
2
1. Introduction
Raman spectroscopy is widely used in characterizing archaeological materials, such as traditional paintings and building decorations. Non-destructive in-situ analysis of pigments in large paintings by mounting the Raman microscope on a scanning gantry is presented by Ernst [1]. With the recent advent of hand-held Raman instruments with relatively good resolution, applicability of the Raman spectroscopy in art and archaeology is even greater [2]. Raman spectroscopic library of pigments of various origins from prehistoric ages are already available [3]. However, Raman measurements on pigments found on Korean heritage are not readily seen. Korean traditional colors are often represented by five basic colors (“Obang” colors); blue, red, yellow, white, and black, meaning east, south, center, west, and north, respectively (Fig. 1). The “Obang” colors are abundantly found in traditional Korean food, costumes, ornaments, paintings, and building decorations. In real paintings and decorations, more diverse colors including orange and green are readily found. In this article, we report a Raman spectroscopic analysis of several kinds of pigments, especially the mineral pigments found in traditional paintings. We have identified the pigments and dye on a 18th -century Buddha painting of the Tongdosa temple, Korea. Our Raman analyses of the pigments and dyes on a Korean traditional painting would be a starting point of similar scientific work on Korean traditional arts, which would eventually be useful in preserving and restoring the valuable Korean cultural heritage.
2. Experimental
Raman spectra of the pigment samples were measured using Horiba Jobin Yvon LabRam Aramis with 532 nm excitation source, Ⅹ10 lens of microscope, 1800 gr/mm-reflective grating with focal length of 450 mm, and Peltier-cooled CCD of 1024Ⅹ256 arrays. The diameter of the focused beam on the sample surface was 2.6 μm. The spectral resolution was
3
found to be about 2.5 cm-1 at 532 nm excitation when the entrance slit was set to 100 µm. For pigments which are photo-degradable, we used high throughput capability of NANOBASE XperRam200 with 1800 lpmm holographic transmissive grating. The spectral resolution of NANOBASE XperRam200 was about 3.0 cm-1 at 532 nm excitation line.
The pigments from the Buddha painting of Tongdosa temple were obtained from the National Research Institute of Cultural Heritage of Korea during the restoration process of the Korean heritage. Fig. 1 shows the Buddha painting of Tongdosa temple with several indications of the location of the pigment sampling. The colors of the pigment or dye samples are denoted in the figure. Even one kind of color is sampled from several locations, and all the seven colors are measured in our Raman measurements. The Tongdosa Buddha painting measured in this study was first completed in 1792 during Yi dynasty by at least 23 artists, and all the information is recorded in the bottom of the painting. The painting was done on silk with several layers of back sheets. The size of the painting is 11.01Ⅹ5.21 m2. The record shows that the back sheets were replaced during the preservation process in 1994, and no other record of previous conservation activity is known. The painting was registered as the Korea treasure No. 1351 in 2002.
Raman spectroscopy is non-destructive when the incident laser power is low enough. However, excessive laser power could not only damage the valuable heritage but also alter the phase or physical and chemical state of the mineral pigments on the paintings during the measurements. For example, strong laser power can blacken the azurite by altering it into the copper oxide (tenorite). Mattei et al. [4] studied the laser-induced degradation of azurite as a function of the particle size. They found that the temperature of the particles decreases as the size increases, and azurite degrades into tenorite only below the critical value of 25 µm. The typical particle sizes of pigments on the paintings are smaller than 25 µm. Therefore extreme care was paid in measuring the Raman spectra of all the pigment samples. NANOBASE XperRam200 was highly effective in throughput so that high signal-to-noise ratio could be achieved even at low laser power. All Raman measurements were done with laser power less than ~0.1 mW/µm2 and excitation time of 10 sec with multiple averaging.
4
3. Results and discussion
Fig. 2 shows Raman spectra of the pigments and dyes obtained from the Tongdosa Buddha painting. The colors measured are blue, red, yellow, white, black, orange, and green. The pigment for blue color is easily identified to be azurite, not smalt, as clearly seen in top part of Fig. 3. The reference Raman spectra of azurite and smalt are taken from RRUFF project website [5]. The RRUFF Project website contains an integrated database of Raman spectra for various minerals, as well as x-ray diffraction and chemistry data for the minerals. The Raman spectra of azurite have been studied extensively by Frost et al. [6]. Azurite is monoclinic in crystal structure, and it is Cu3(CO3)2(OH)2 in chemical formula. The characteristic mode at ~400 cm-1 is Cu-O stretching mode, and most of the Raman modes above ~700 cm-1 are from the hydroxyl group and carbonate group in the azurite crystal structure. It has been used as a pigment for blue color from ancient time, as found in cave paintings at Dunhuang in Western China and wall paintings in Central China from the Tang and Song dynasties. It was also the most important blue pigment in European painting throughout the middle ages and Renaissance. On the other hand, smalt is an artificial blue pigment, potassium glass containing small amounts of cobalt oxide, and it was widely used in Europe as early as 16th century because of its low cost in manufacturing. It has been often used as a blue pigment in 11th - 13th century Chinese wall painting and became widespread in the 16th - 17th-centuries [7]. In the bottom of Fig. 3, the Raman spectrum for the yellow color of the Tongdosa Buddha is shown along with those of gamboge and goethite. The Raman spectrum of gamboge from Ref. [8] matches well with that from the yellow part of the Tongdosa Buddha painting, which is much different from the spectrum of goethite, FeO(OH), taken from RRUFF project webpage. Gamboge is a yellow dye, composed of gamboge acids, C38H44O8 and C29H36O6 , extracted by tapping resin from the gamboge tree.
Fig. 4 shows the Raman spectra of the Tongdosa pigments for red, white, black, orange, and green colors, along with reference Raman spectra for various materials as denoted. By comparing with the reference Raman spectra, the pigment for red color is cinnabar, mercury(II) sulfide HgS in chemical formula. The Raman spectrum for hematite is completely
5
different from that of Tongdosa red pigment. The pigments for the white and black are identified as hydrocerussite (lead white) and amorphous carbon, respectively. Hydrocerussite or lead white, 2PbCO3-Pb(OH)2 in chemical formula, has characteristic Raman peaks at 326, 416, 680, and 1051 cm-1.[9] The Raman spectrum of the pigment for white color on the Tongdosa Buddha painting is matching with that from lead white as depicted in the Fig. 4. Burgio et al. studied the Raman spectra of various lead oxides including lead white and their laser-induced degradation products [9]. Note that the spectrum from the white pigment is much different from that of calcite. Amorphous carbon is used as black pigment in paintings east and west as well. It is known to have broad Raman peaks at 1350 (D-peak) and 15801600 (G-peak) cm-1 [10, 11]. The black color in the Tongdosa Buddha painting is surely from the amorphous carbon. The Raman spectrum from the orange pigment on the Tongdosa Buddha painting matches with that of minium, and the green pigment with that of botallackite as seen in the bottom of the figure. Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4 also known as red lead. Botallackite is mineral containing copper, Cu2Cl(OH)2 in chemical formula, which is different from malachite, a copper carbonate hydroxide mineral with the formula Cu2CO3(OH)2 although similar in green color. In summary, a Raman spectroscopic analysis of several kinds of mineral pigments from a Korean traditional Buddha painting is presented. We could identify several pigments from a 18th -century Buddha painting of the Tongdosa temple. The Raman spectra of the blue pigment on the Tongdosa Buddha painting show that it is azurite, not smalt which was prevalent then. The pigments for the yellow, red, white, and black colors are identified as gamboge, cinnabar, hydrocerussite, and amorphous carbon, respectively. The orange and green pigments are found to be minium and botallackite, respectively. There are many different minerals even for the same color. Therefore, identifying the pigments precisely is the first step in assessing the valuable traditional paintings. Our Raman spectroscopic analyses of the pigments on Korean traditional paintings would provide a useful scientific basis for the preservation and restoration of the cultural heritage.
Acknowledgement Authors thank the National Research Institute of Cultural Heritage of Korea for the financial aid (grant number:15F006Y-00120-2015).
6
References [1] R. R. Ernst, J. Raman Spectrosc. 41 (2010) 275–287. [2] D. Bersani, J.M. Madariaga, J. Raman Spectrosc. 43 (2012) 1523–1528. [3] I.M. Bell, Robin J.H. Clark, P.J. Gibbs, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 53 (1997) 2159–2179. [4] E. Mattei, G. de Vivo, A. De Santis, C. Gaetani, C. Pelosi and U. Santamaria, J. Raman Spectrosc. 39, (2008) 302 . [5] B. Lafuente, R.T. Downs, H. Yang, N. Stone, The power of databases: the RRUFF project. in Highlights in Mineralogical Crystallography, T Armbruster and R M Danisi, eds. Berlin, Germany, W. De Gruyter, pp 1-30 (2015). [6] R.L. Frost, W.N. Martens, L. Rintoul, E. Mahmutagic, J.T. Kloprogge, J. Raman Spectrosc. 33 (2002), 252-259. [7] CAMEO: Conservation & Art Materials Encyclopedia Online, Museum of Fine Arts Boston, http://cameo.mfa.org/wiki/Smalt [8] Ian M. Bell, Robin J.H. Clark, and Peter J. Gibbs, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 53 (1997) 2159–2179. [9] L. Burgio, R. J. H. Clark, S. Firth, Analyst 126 (2001) 222-227. [10] P.K. Chu, L. Li, Materials Chemistry and Physics 96 (2006) 253–277. [11] R. T. Mayes, C. Tsouris, J. O. Kiggans Jr, S. M. Mahurin, D. W. DePaoli, S. Dai, J. Mater. Chem. 20 (2010) 8674–8678.
7
Figure captions Fig. 1. The Buddha painting of Tongdosa temple with several indications of the location of the pigment sampling. The colors of the pigment or dye samples are denoted.
8
Fig. 2. Raman spectra of the pigments from the Tongdosa Buddha painting.
9
Fig. 3. (Top) Raman spectrum of the blue pigment from the Tongdosa Buddha painting along with reference Raman spectra of azurite and smalt taken from the RRUFF database.(Bottom) Raman spectrum of the pigment for yellow color along with the reference Raman spectra for gamboge and goethite.
10
Fig. 4. Raman spectra of the Tongdosa pigments for red, white, black, orange, and green colors, along with reference Raman spectra for various materials as denoted.
11
S0924-2031(16)30075-3 http://dx.doi.org/doi:10.1016/j.vibspec.2016.04.011 VIBSPE 2546
To appear in:
VIBSPE
Received date: Revised date: Accepted date:
13-10-2015 23-2-2016 20-4-2016
Please cite this article as: Ji-Yeon Nam, Kiok Han, Jeong-Eun Ji, Seung Kim, Hanhyoung Lee, Daiill Kang, Minsu Han, In-Sang Yang, Raman spectroscopy of the pigments on Korean traditional paintings, Vibrational Spectroscopy http://dx.doi.org/10.1016/j.vibspec.2016.04.011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Raman spectroscopy of the pigments on Korean traditional paintings
Ji-Yeon Nama, Kiok Hana, Jeong-Eun Jia, Seung Kima, Hanhyoung Leeb, Daiill Kangb, Minsu Hanc, In-Sang Yanga,*
a
Department of Physics and Division of Nano-Sciences, Ewha Womans University, Seoul
120-750, Korea b
Department of Conservation Science, Korea National University of Cultural Heritage,
Buyeo 323-812, Korea c
Conservation Science Division, National Research Institute of Cultural Heritage, Daejeon
341-22, Korea
*Corresponding author. Tel. +82-2-3277-2332, fax: +82-2-3277-2372; E-mail address: [email protected] (I.-S. Yang).
1
Highlights;
Raman spectroscopy of the pigments used in paintings of Korean heritage.
Identified some of the pigments on a Buddha painting of the Tongdosa temple, Korea.
Results would provide a useful scientific basis for the preservation of cultural heritages.
ABSTRACT Raman spectroscopy is now a well-established tool in characterizing archaeological materials, such as traditional paintings. In this report, we applied Raman spectroscopy to investigate the pigments used in Korean traditional paintings. Korean traditional colors are often represented by the five basic colors; blue, red, yellow, white, and black. In real paintings, the colors are more diverse including orange and green. We report a Raman spectroscopy of the various pigments found in Korean traditional paintings. Raman spectra are used to identify the several components of minerals in the pigments if they are mixtures of different minerals. Our work would provide a useful scientific basis for the conservation and restoration of aged and damaged Korean traditional heritages.
Keywords: Traditional pigments, Mineral pigments; Raman spectroscopy; Traditional painting; Nondestructive measurements; Vibrational spectroscopy
2
1. Introduction
Raman spectroscopy is widely used in characterizing archaeological materials, such as traditional paintings and building decorations. Non-destructive in-situ analysis of pigments in large paintings by mounting the Raman microscope on a scanning gantry is presented by Ernst [1]. With the recent advent of hand-held Raman instruments with relatively good resolution, applicability of the Raman spectroscopy in art and archaeology is even greater [2]. Raman spectroscopic library of pigments of various origins from prehistoric ages are already available [3]. However, Raman measurements on pigments found on Korean heritage are not readily seen. Korean traditional colors are often represented by five basic colors (“Obang” colors); blue, red, yellow, white, and black, meaning east, south, center, west, and north, respectively (Fig. 1). The “Obang” colors are abundantly found in traditional Korean food, costumes, ornaments, paintings, and building decorations. In real paintings and decorations, more diverse colors including orange and green are readily found. In this article, we report a Raman spectroscopic analysis of several kinds of pigments, especially the mineral pigments found in traditional paintings. We have identified the pigments and dye on a 18th -century Buddha painting of the Tongdosa temple, Korea. Our Raman analyses of the pigments and dyes on a Korean traditional painting would be a starting point of similar scientific work on Korean traditional arts, which would eventually be useful in preserving and restoring the valuable Korean cultural heritage.
2. Experimental
Raman spectra of the pigment samples were measured using Horiba Jobin Yvon LabRam Aramis with 532 nm excitation source, Ⅹ10 lens of microscope, 1800 gr/mm-reflective grating with focal length of 450 mm, and Peltier-cooled CCD of 1024Ⅹ256 arrays. The diameter of the focused beam on the sample surface was 2.6 μm. The spectral resolution was
3
found to be about 2.5 cm-1 at 532 nm excitation when the entrance slit was set to 100 µm. For pigments which are photo-degradable, we used high throughput capability of NANOBASE XperRam200 with 1800 lpmm holographic transmissive grating. The spectral resolution of NANOBASE XperRam200 was about 3.0 cm-1 at 532 nm excitation line.
The pigments from the Buddha painting of Tongdosa temple were obtained from the National Research Institute of Cultural Heritage of Korea during the restoration process of the Korean heritage. Fig. 1 shows the Buddha painting of Tongdosa temple with several indications of the location of the pigment sampling. The colors of the pigment or dye samples are denoted in the figure. Even one kind of color is sampled from several locations, and all the seven colors are measured in our Raman measurements. The Tongdosa Buddha painting measured in this study was first completed in 1792 during Yi dynasty by at least 23 artists, and all the information is recorded in the bottom of the painting. The painting was done on silk with several layers of back sheets. The size of the painting is 11.01Ⅹ5.21 m2. The record shows that the back sheets were replaced during the preservation process in 1994, and no other record of previous conservation activity is known. The painting was registered as the Korea treasure No. 1351 in 2002.
Raman spectroscopy is non-destructive when the incident laser power is low enough. However, excessive laser power could not only damage the valuable heritage but also alter the phase or physical and chemical state of the mineral pigments on the paintings during the measurements. For example, strong laser power can blacken the azurite by altering it into the copper oxide (tenorite). Mattei et al. [4] studied the laser-induced degradation of azurite as a function of the particle size. They found that the temperature of the particles decreases as the size increases, and azurite degrades into tenorite only below the critical value of 25 µm. The typical particle sizes of pigments on the paintings are smaller than 25 µm. Therefore extreme care was paid in measuring the Raman spectra of all the pigment samples. NANOBASE XperRam200 was highly effective in throughput so that high signal-to-noise ratio could be achieved even at low laser power. All Raman measurements were done with laser power less than ~0.1 mW/µm2 and excitation time of 10 sec with multiple averaging.
4
3. Results and discussion
Fig. 2 shows Raman spectra of the pigments and dyes obtained from the Tongdosa Buddha painting. The colors measured are blue, red, yellow, white, black, orange, and green. The pigment for blue color is easily identified to be azurite, not smalt, as clearly seen in top part of Fig. 3. The reference Raman spectra of azurite and smalt are taken from RRUFF project website [5]. The RRUFF Project website contains an integrated database of Raman spectra for various minerals, as well as x-ray diffraction and chemistry data for the minerals. The Raman spectra of azurite have been studied extensively by Frost et al. [6]. Azurite is monoclinic in crystal structure, and it is Cu3(CO3)2(OH)2 in chemical formula. The characteristic mode at ~400 cm-1 is Cu-O stretching mode, and most of the Raman modes above ~700 cm-1 are from the hydroxyl group and carbonate group in the azurite crystal structure. It has been used as a pigment for blue color from ancient time, as found in cave paintings at Dunhuang in Western China and wall paintings in Central China from the Tang and Song dynasties. It was also the most important blue pigment in European painting throughout the middle ages and Renaissance. On the other hand, smalt is an artificial blue pigment, potassium glass containing small amounts of cobalt oxide, and it was widely used in Europe as early as 16th century because of its low cost in manufacturing. It has been often used as a blue pigment in 11th - 13th century Chinese wall painting and became widespread in the 16th - 17th-centuries [7]. In the bottom of Fig. 3, the Raman spectrum for the yellow color of the Tongdosa Buddha is shown along with those of gamboge and goethite. The Raman spectrum of gamboge from Ref. [8] matches well with that from the yellow part of the Tongdosa Buddha painting, which is much different from the spectrum of goethite, FeO(OH), taken from RRUFF project webpage. Gamboge is a yellow dye, composed of gamboge acids, C38H44O8 and C29H36O6 , extracted by tapping resin from the gamboge tree.
Fig. 4 shows the Raman spectra of the Tongdosa pigments for red, white, black, orange, and green colors, along with reference Raman spectra for various materials as denoted. By comparing with the reference Raman spectra, the pigment for red color is cinnabar, mercury(II) sulfide HgS in chemical formula. The Raman spectrum for hematite is completely
5
different from that of Tongdosa red pigment. The pigments for the white and black are identified as hydrocerussite (lead white) and amorphous carbon, respectively. Hydrocerussite or lead white, 2PbCO3-Pb(OH)2 in chemical formula, has characteristic Raman peaks at 326, 416, 680, and 1051 cm-1.[9] The Raman spectrum of the pigment for white color on the Tongdosa Buddha painting is matching with that from lead white as depicted in the Fig. 4. Burgio et al. studied the Raman spectra of various lead oxides including lead white and their laser-induced degradation products [9]. Note that the spectrum from the white pigment is much different from that of calcite. Amorphous carbon is used as black pigment in paintings east and west as well. It is known to have broad Raman peaks at 1350 (D-peak) and 15801600 (G-peak) cm-1 [10, 11]. The black color in the Tongdosa Buddha painting is surely from the amorphous carbon. The Raman spectrum from the orange pigment on the Tongdosa Buddha painting matches with that of minium, and the green pigment with that of botallackite as seen in the bottom of the figure. Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4 also known as red lead. Botallackite is mineral containing copper, Cu2Cl(OH)2 in chemical formula, which is different from malachite, a copper carbonate hydroxide mineral with the formula Cu2CO3(OH)2 although similar in green color. In summary, a Raman spectroscopic analysis of several kinds of mineral pigments from a Korean traditional Buddha painting is presented. We could identify several pigments from a 18th -century Buddha painting of the Tongdosa temple. The Raman spectra of the blue pigment on the Tongdosa Buddha painting show that it is azurite, not smalt which was prevalent then. The pigments for the yellow, red, white, and black colors are identified as gamboge, cinnabar, hydrocerussite, and amorphous carbon, respectively. The orange and green pigments are found to be minium and botallackite, respectively. There are many different minerals even for the same color. Therefore, identifying the pigments precisely is the first step in assessing the valuable traditional paintings. Our Raman spectroscopic analyses of the pigments on Korean traditional paintings would provide a useful scientific basis for the preservation and restoration of the cultural heritage.
Acknowledgement Authors thank the National Research Institute of Cultural Heritage of Korea for the financial aid (grant number:15F006Y-00120-2015).
6
References [1] R. R. Ernst, J. Raman Spectrosc. 41 (2010) 275–287. [2] D. Bersani, J.M. Madariaga, J. Raman Spectrosc. 43 (2012) 1523–1528. [3] I.M. Bell, Robin J.H. Clark, P.J. Gibbs, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 53 (1997) 2159–2179. [4] E. Mattei, G. de Vivo, A. De Santis, C. Gaetani, C. Pelosi and U. Santamaria, J. Raman Spectrosc. 39, (2008) 302 . [5] B. Lafuente, R.T. Downs, H. Yang, N. Stone, The power of databases: the RRUFF project. in Highlights in Mineralogical Crystallography, T Armbruster and R M Danisi, eds. Berlin, Germany, W. De Gruyter, pp 1-30 (2015). [6] R.L. Frost, W.N. Martens, L. Rintoul, E. Mahmutagic, J.T. Kloprogge, J. Raman Spectrosc. 33 (2002), 252-259. [7] CAMEO: Conservation & Art Materials Encyclopedia Online, Museum of Fine Arts Boston, http://cameo.mfa.org/wiki/Smalt [8] Ian M. Bell, Robin J.H. Clark, and Peter J. Gibbs, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 53 (1997) 2159–2179. [9] L. Burgio, R. J. H. Clark, S. Firth, Analyst 126 (2001) 222-227. [10] P.K. Chu, L. Li, Materials Chemistry and Physics 96 (2006) 253–277. [11] R. T. Mayes, C. Tsouris, J. O. Kiggans Jr, S. M. Mahurin, D. W. DePaoli, S. Dai, J. Mater. Chem. 20 (2010) 8674–8678.
7
Figure captions Fig. 1. The Buddha painting of Tongdosa temple with several indications of the location of the pigment sampling. The colors of the pigment or dye samples are denoted.
8
Fig. 2. Raman spectra of the pigments from the Tongdosa Buddha painting.
9
Fig. 3. (Top) Raman spectrum of the blue pigment from the Tongdosa Buddha painting along with reference Raman spectra of azurite and smalt taken from the RRUFF database.(Bottom) Raman spectrum of the pigment for yellow color along with the reference Raman spectra for gamboge and goethite.
10
Fig. 4. Raman spectra of the Tongdosa pigments for red, white, black, orange, and green colors, along with reference Raman spectra for various materials as denoted.
11