- Email: [email protected]
Analytical study of Saint Gregory Nazianzen Icon, Old Cairo, Egypt
Journal of Molecular Structure 1100 (2015) 70e79
Contents lists available at ScienceDirect
Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc
Analytical study of Saint Gregory Nazianzen Icon, Old Cairo, Egypt Yousry M. Issa a, Gomaa Abdel-Maksoud b, *, Mina Magdy c a
Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt Conservation Department, Faculty of Archeology, Cairo University, Giza, 12613, Egypt c National Museum of Egyptian Civilization, Cairo, Egypt b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 May 2015 Received in revised form 2 July 2015 Accepted 3 July 2015 Available online 15 July 2015
The study aims to evaluate the state of icon through characterization of the icon layers (ground, paint and varnish layers) and to provide tools for assessment the impact of aging and environmental conditions in order to produce some solutions for conservation of the icon. Analytical techniques used in this study were attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscope-energy dispersive X ray spectroscopy (FESEM-EDX) and amino acid analyzer (AAA). The results obtained revealed that gypsum and lead white were used for ground layer. The identified pigments were lamp carbon black, brown ochre, Prussian blue, yellow ochre and gold leaf. Egg yolk was the binder used with most of pigments and animal glue was used with gold color. The varnish used was shellac resin. It was concluded that stable pigments gave permanent colors and environmental conditions had an influence on promotion of oxidation process. Auto-oxidation of binder and varnish materials occurred by the action of pigment components and light result in cracking of the paint film and fading of the varnish glaze. © 2015 Published by Elsevier B.V.
Keywords: Icon ATR-FTIR FESEM-EDX AAA Deterioration
1. Introduction Icons carry a lot of spiritual meaning in our lives. The art of icons presents symbolism of one or several events that carries a meaningful message [1]. The Icons are described as fruits of the Coptic art. Icons are composed of four layers: support, ground, paint “pigments and binder” and varnish layer. The support is the surface upon which the paint is applied [2]. The ground layer, also known as the primer or preparation layer, is the layer on which a drawing is made before the paint is applied [3]. The paint is a colored fluid preparation that is applied as a thin coating to the surface of solid materials. Generally, paint is mixture of at least three basic components: a pigment, a medium and a binder. Pigments are finely powdered solids used to impart color to other materials [4]. Medium, also known as vehicle or diluent, provides the material agent in which the other components of the paint are either dissolved or suspended [2,4]. Binder, also known as the binding medium or film former, is the component that binds the particles of pigment to each other and to the painted surface [4]. The varnish is a
* Corresponding author. E-mail addresses: [email protected] (Y.M. Issa), gomaaabdelmaksoud@ yahoo.com (G. Abdel-Maksoud), [email protected] (M. Magdy). http://dx.doi.org/10.1016/j.molstruc.2015.07.004 0022-2860/© 2015 Published by Elsevier B.V.
transparent material used to protect the paint layers and to provide the gloss of paint colors [3]. Deterioration of paintings is defined as a gradual decomposition of the chemical structure and physical integrity of the icon materials with time. This may be a result of environmental effects such as heat, sunlight, weathering, bacterial action, pollutants, or human activity [5]. Chemicals used in pigments can have a notable effect on binder and varnish materials because they promote lightinduced oxidation reactions [6]. Multi-techniques with high spatial resolutions are required for characterization of the icon layers and observation of the degradation products that associate with natural aging and concomitant effect of the environmental conditions. Attenuated total reflectionFourier transform infrared spectroscopy (ATR-FTIR) gives information about both organic and inorganic components in the paint and their degradation. Field emission scanning electron microscopy (FESEM) can be used for examination of the icon materials. The surface characteristics of painting can be investigated using electron imaging. Energy dispersive spectroscopy (EDS) gives information about elemental composition of the icon components. Amino acid analyzer (AAA) is used for identification of proteinaceous binding medium and observing the change of amino acids concentration [3]. The analysis and investigation used in this study will help the
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
71
conservator to make accurate conservation treatment especially in the process of completion of missed parts or in gap filling of cracks by using the same materials used in the icon components. They are also useful to determine the causes of deterioration forms, which help the conservators to make good preventive conservation (controlling of the surrounding environmental conditions such as light, temperature, relative humidity and etc.). The aim of present work is to analyze the icon layers (ground, paint and varnish layers) by multi-techniques in order to identify the chemical composition of icon materials and describe the influence of environmental conditions. After that, the conservator will have the ability to make very good plan for conservation of the icon. 1.1. Historical background Icon of Saint Gregory Nazianzen is located in church of Saint George, Monastery of Saint Mina (South of Cairo). The icon dates back to 18th century. It is believed to have been drawn by painter from school of Ibrahim El-Naseh and Yuhanna Al-Armani. 1.2. Icon description Icon of Saint Gregory Nazianzen (Fig. 1) is characterized by its bright colors and accurate implementation. Saint Gregory wears sticharion with blue color at upper part, red color at lower part and gray-color tailasan with crown on his head. The Saint Gregory also holds golden cross in his right hand and black stick in his left hand. There is a golden halo around his head. The Saint stands with yellow background. Name of Saint Gregory mentioned in the painting of icon with black color. The icon shows sever longitudinal and transversal fractures of the wood support. 2. Experimental data 2.1. Materials 2.1.1. Historical samples Seven micro samples were carefully taken from the fallen parts of damaged icon. The samples colors were white, black, brown, gray, blue, yellow and gold colors. The authors were not able to get sample from the support of icon. 2.1.2. Reference samples Seven fresh samples of ground (gypsum and lead white), binder (egg yolk and animal glue), pigments (lamp carbon, iron oxide “mars yellow”), varnish (shellac resin) and aluminum silicate (kaolin) materials were assembled and analyzed by ATR-FTIR method, while Prussian blue was obtained from library of Bio-Rad system [7]. Egg yolk reference sample was also analyzed by AAA method for comparison with the historical sample.
Fig. 1. Icon of Saint Gregory Nazianzen.
field emission scanning electron microscope (Quanta FEG-250, FEI Company, Hillsboro, Oregon, USA) equipped with EDX unit (Energy Dispersive X-ray Spectrophotometer, EDAX Apollo SDD, Mahwah, New Jersey, USA), with low-vacuum mode, accelerating voltage 20 kV, magnification 14 up to1,000,000 and resolution of 1 nm.
2.2. Methods 2.2.1. Attenuated total reflection Fourier transform infrared (ATRFTIR) spectroscopy Mid Infrared (MIR) spectra are recorded with a Vertex 70 FTIR spectrometer (Bruker Optics, Billerica Inc., Massachusetts, USA) equipped with a diamond ATR system. The spectra were acquired with 16 scans in the wavenumber range from 400 to 4000 cm1 and room temperature DLaTGS detector at 4 cm1 spectral resolution. 2.2.2. Field emission scanning electron microscopy-energy dispersive X-Ray spectroscopy (FESEM-EDX) Scanning electron microscopy (SEM) images were taken using
2.2.3. Amino acid analyzer (AAA) The chromatographic analysis of proteinaceous binder was carried on an LC 3000 amino acid analyzer (Eppendorf, Hamburg, Germany). The separation system comprised of a cooled compartment for autosampler, 4 buffer bottles, ninhydrin, washing solution, helium-inert gas manifold for the solutions, heating compartment for analytical column and derivatization-reactor, as well as twochannel photometric detection. The chromatographic separation was achieved with a cation exchange column BTC 2410-4 mm, 125 4 mm and lithium citrate buffer system. The device was controlled by WinLC combined with EZChrom data software. Samples were analyzed with 6 N HCl at 110 C in Teflon-capped
72
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Table 1 Infrared bands of the reference samples. Material
Band (cm1), (Assignment)
Gypsum [8] Lead White Prussian Blue Iron Oxide (Mars Yellow) Aluminum Silicate (Kaolin) Egg Yolk [8] Animal Glue Shellac Resin
2 3606, 3551 y(OeH), 1110, 1087, 1007 y(SO2 4 ), 658 d(SO4 ) 3344 y(OeH), 1642 d(OeH), 1033 y(CO2 3 ) 2082 y(C^N) 793, 711, 667 y(FeeO) 3689, 3649, 3620 y(OeH), 1026, 999 y(SieOeSi), y(SieOeAl), 910 y(AleOeH) 3282 y(NeH), 2923, 2853 y(CeH), 1744, 1633 y(C]O), 1541, 669 d(NeH), 1541 y(CeN), 1458, 1416, 1378 d(CeH) 2928, 2867 y(CeH), 1691 y(C]O), 1460, 1446, 1385 d(CeH) 3376 y(OeH), 2920, 2852 y(CeH), 1709, 1635 y(C]O), 1635 d(OeH), 1463, 1414, 1374 d(CeH), 1247, 1146, 1111, 1002, 943, 927 y(CeO)
vials for 24 h. After vacuum removal of HCl, the residue was dissolved in a lithium citrate buffer. 20 mL of the solution were loaded onto the cation exchange column, then four buffer system was applied with increased pH and it followed by post column reaction with ninhydrin. The ninhydrin flow rate was 0.2 mL/min at pressure of 0e50 bar. Detection carried out at 570 nm (Channel A) and in case of fault of detection or high concentration detection on a second channel (Channel B) at 470 nm.
3. Results and discussion Infrared bands of the historical samples (Table 1) will be compared to the bands of reference samples (Table 2). Energy dispersive X-ray spectroscopy (Table 3) detects the elemental composition of each paint color. Meanwhile, Scanning electron microscope (Fig. 2) gives images about the surface of paint colors. The study of paint layers of Saint Gregory Nazianzen by ATRFTIR, FESEM-EDX and AAA methods reveals that the ground material are gypsum and lead white, the binder is egg yolk, the varnish is shellac resin and animal glue is a binder agent for the bole leaf. Gypsum manifests ATR-FTIR bands at 3700e3399 cm1 y(OeH),
1649e1647 cm1 d(OeH), 1113e1110 cm1 y(SO2 and 4 ) 669e667 cm1 d(SO2 4 ) [9e11]. EDS microanalysis detects Ca, S and O elements which are characteristic of gypsum [12]. ATR-FTIR analysis exhibits lead white at 3700e3399 cm1 y(OeH), 1649e1647 cm1 d(OeH), 1429e1418 cm1 y(CO2 3 ) and 875e874 cm1 d(CO2 3 ) [11], [13e15]. EDS microanalysis detects Pb element which is characteristic of lead white [12]. FESEM micrograph shows bright particles of lead white. Egg yolk shows characteristic bands at 3402e3396 cm1 y(NeH), 2924e2849 cm1 y(CeH), 1732e1541 cm1 y(C]O), 1541, 669e667 cm1 d(NeH), 1541 cm1 y(CeN) and 1429e1324 cm1 d(CeH) [16e19]. EDS microanalysis detects P element as one component of egg yolk (phosphoprotein and phospholipid) [20] and ATR-FTIR spectrum exhibits phosphate band at 1030e1019 cm1 [21]. ATR-FTIR analysis exhibits bands for animal glue at 3396 cm1 y(NeH), 2919, 2852 cm1 y(CeH), 1620 cm1 y(C]O), 1541, 667 cm1 d(NeH) and 1418 cm1 d(CeH) [11,22,23]. Shellac resin is proved by appearance of ATR-FTIR bands at 3700e3399 cm1 y(OeH), 2924e2849 cm1 y(CeH), 1 1732e1620 cm y(C]O), 1649e1620 cm1 y(CeC),
Table 2 Infrared bands of the paint colors of historical samples. Color
Characteristic bands (cm1) in IR spectra
Material
White
3516, 1106, 1054, 667 3516, 1426, 874 3530, 3402, 1649, 1113 3530, 3402, 1649, 1429, 3402, 2924, 2853, 1649, 3530, 3402, 2924, 2853, 3700, 3530, 3399, 1647, 3700, 3530, 3399, 1647, 793, 669 3700, 3530, 3399, 1021, 3399, 2922, 2852, 1732, 3399, 2922, 2852, 1732, 3529, 3400, 1111, 669 3529, 3400, 1426, 875 3400, 2919, 2851, 1731, 3529, 3400, 2919, 2851, 3537, 3402, 1649, 1112, 3537, 3402, 1649, 1428, 2087 3402, 2922, 2852, 1730, 3537, 3403, 2922, 2852, 3396, 1648, 1110, 667 3396, 1648, 1422, 873 792, 711, 667 3396, 1020, 948, 873 3396, 2918, 2849, 1732, 3396, 2918, 2849, 1732, 3524, 1104, 667 3524, 1418, 873 3396, 2919, 2852, 1620, 3524, 3396, 2919, 2852,
Gypsum Lead White Gypsum Lead White Egg Yolk Shellac Resin Gypsum Lead White Iron Oxide Aluminum Silicate Egg Yolk Shellac Resin Gypsum Lead White Egg Yolk Shellac Resin Gypsum Lead White Prussian Blue Egg Yolk Shellac Resin Gypsum Lead White Iron Oxide Aluminum Silicate Egg Yolk Shellac Resin Gypsum Lead White Animal Glue Shellac Resin
Black
Brown
Gray
Blue
Yellow
Gold
874 1429, 1730, 1112, 1427,
1371 1649, 1429, 1371, 1231, 1113, 1020, 947 669 875
875 1647, 1622, 1541, 1427, 1372, 1324, 669 1647, 1622, 1427, 1372, 1324, 1233, 1112, 1021, 947
1620, 1426, 1372, 1324, 669 1731, 1620, 1426, 1372, 1324, 1234, 1111, 1019 669 874 1649, 1621, 1428, 1371, 669 1730, 1649, 1621, 1428, 1371, 1232, 1112, 1020, 947
1648, 1622, 1541, 1422, 1372, 667 1648, 1622, 1422, 1372, 1232, 1110, 1020, 948
1541, 1418, 667 1732, 1620, 1418, 1339, 1104
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79 Table 3 EDS microanalysis and elemental composition (atomic percentage) of each color of historical sample. Element
White
Black
Brown
Gray
Blue
Yellow
Gold
CK OK Na K Mg K Al K Ca K Si K SK Cl K KK PK Fe K Pb L Ba L Ti K Zn K Cr K As L NK Au L Cu K
38.30 49.69 0.45 0.36 0.55 4.55 0.98 4.34 0.52 e e 0.11 0.15 e e e e e e e e
62.14 25.82 e 0.44 0.74 1.18 0.82 1.69 1.66 0.18 0.21 e 0.32 1.36 e 0.40 2.34 e e e 0.70
59.63 30.80 0.83 0.35 3.62 0.93 0.83 e 1.29 0.25 0.41 0.14 0.84 e e e e e e 0.09 e
46.17 27.61 e 0.67 1.72 2.68 2.11 6.71 1.28 e e 0.55 e 8.28 e 2.23 e e e e e
47.77 32.34 0.29 0.15 1.15 1.88 1.71 4.83 0.87 0.24 0.21 0.29 0.61 2.22 3.87 1.58 e e e e e
58.58 29.54 1.05 e 1.13 2.77 0.93 2.22 0.91 0.26 0.18 0.32 e 1.76 e e e 0.36 e e e
48.71 7.47 e e 0.88 1.64 1.24 e e 0.18 e e e e e e e e 14.29 24.55 1.05
1429e1324 cm1 d(CeH) and 1324e947 cm1 y(CeO) [11,24,25]. All colors give the same chemical composition regarding the ground, the binder, and the varnish materials. 1 White color Fibers of paper appear within FESEM micrograph (Fig. 2A) as a flexible support for the paint layers and it is characteristic with ribbon-twisted structure that is remarkable to cotton fibers [26,27]. The fibers appear randomly with good distribution of the filler and the distance between fibers is very close [28]. There are tears due to the natural aging of fibers. In general, the state of most fibers is
73
good and this illustrates that area is a good climate for the icon with adjustment the environmental conditions. ATR-FTIR spectrum of (Fig. 3) shows characteristic bands of gypsum and lead white. EDS microanalysis (Fig. 4) detects Pb element of lead white and Ca, S and O elements of gypsum. FESEM micrograph (Fig. 2B) shows fracture crystals of calcium sulfate (gypsium), lead carbonate (lead white). White color shows that sample without paint and varnish layers. 2 Black color EDS microanalysis (Table 3) shows a high carbon content, which indicates the presence of carbon organic material. Carbon black has no characteristic infrared bands (Fig. 5). Carbon black is a common name for black pigment that made of plant materials or soot lamps [29]. FESEM micrograph (Fig. 2C) shows the paint surface is homogenous and smooth without globular particles or rough topography, so carbon black may be lamp black pigment [30e32]. Carbon black has a protecting influence against the light [5]. EDS microanalysis detects Ba, S and O elements of barite as extender with carbon black pigment, ATR-FTIR spectrum shows sulfate bands at 1113 cm1 [33,34]. Black pigment contains zinc element as impurities and copper element as contamination from palette's artist. A high amount of Chromium element may be attributed to contamination from artist's brush and this demonstrates usage of chromate pigment in painting of the icon and dates the icon to late 18th century or early 19th century. 3 Brown color EDS microanalysis (Table 3) did not detect Mn element so the use of umber and sienna pigments can be excluded. Brown color shows ATR-FTIR bands (Fig. 6) at 793 and 669 cm1 that refer to iron oxide [35,36] and bands at 1021 and 875 cm1 that refer to aluminum silicate [17,37]. FESEM micrograph (Fig. 2D) shows fracture of aluminosilicate crystals. EDS microanalysis detects Al,
Fig. 2. FESEM micrograph of historical samples: (A) paper support; (B) white color; (C) black color; (D) brown color; (E) gray color; (F) blue color; (G) yellow color; (H) gold color. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
74
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 3. ATR-FTIR spectra of: (1) historical sample “white color”; (2) gypsum; (3) Lead white.
Fig. 4. EDX spectrum and elemental composition of white color. (Representative Figure).
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
75
Fe, Si and O elements [37,38]. Ochre pigment is a natural pigment or synthetic iron oxide (Fe2O3) and kaolin clay (aluminum silicate, Al2Si2O5(OH)4) [29,39]. It can be concluded that brown pigment is ochre pigment (brown ochre). Brown color may be result of calcining the yellow ochre at certain temperature or mixing of yellow ochre with carbon black causing change the tone of the pigment to brown [37,39]. Brown pigment contains gold element as contamination from palette's artist. Presence of metal oxide and other salts have a role in promotion of light-induced oxidation for organic materials causing cracking of the paint film and fading of the varnish glaze [6,40e42]. Iron ions can form complexes with egg yolk protein, shellac resin and it acts as catalyst for oxidation of the binder and varnish materials. This assumption can be confirmed by presence of infrared bands of oxalate at 1622 and 1324 cm1 [14,43]. 4 Gray color Gray color may be a result of mixing white and black pigments. This assumption is confirmed by EDS microanalysis (Table 3) showing a high carbon content of carbon black pigment and a high percentage of calcium, silicon, aluminum, and oxygen elements of calcium sulfate and lead carbonate of white ground materials. ATRFTIR spectrum of gray color (Fig. 7) exhibits characteristic bands of gypsum and lead white of white pigment with no characteristic bands of carbon black pigment. FESEM micrograph (Fig. 2E) shows flakes of calcium sulfate and lead carbonate. EDS microanalysis detects Ba, S and O elements of barite as extender with the pigments, ATR-FTIR spectrum shows sulfate bands at 1111 cm1 [33,34]. Gray pigment contains zinc element as impurities for barite. Gray color shows fading of the varnish glaze due to presence of calcium salts, which promote light-induced oxidation [6,40e42]. Calcium salts of white pigment cause degradation of the egg yolk binder and shellac resin through association of Caþ2 ions with free carboxyl group of the organic materials producing calcium oxalate. This assumption can be confirmed by infrared bands of calcium oxalate at 1620 and 1324 cm1 [14,43]. Amino acid analysis of gray color (Table 4) exhibits distinctive concentration of amino acids: phenylalanine (20.34%), alanine (14.89%), proline (14.39%), glutamic acid (9.72%), serine (9.30%), cystine (8.39%), threonine (7.42%), glycine (5.88%), isoleucine (3.54%), histidine (2.24%), aspartic acid (1.60%), tyrosine (1.00%), arginine (0.62%), valine (0.42%) and leucine (0.27%). The results obtained shows that content of some amino acids of gray color are reduced (aspartic acid, glutamic acid, valine, leucine, tyrosine, histidine and arginine) or zeroed (lysine and methionine) as a result of oxidation process. 5 Blue color ATR-FTIR spectrum (Fig. 8) shows band at 2087 cm1, which is characteristic for Prussian blue [10,12,44]. FESEM micrograph (Fig. 2F) shows small particles of Prussian blue. EDS microanalysis detects Ba, S and O elements of barite as extender with Prussian blue pigment, ATR-FTIR spectrum shows sulfate bands at 1112 cm1 [33,34]. Blue pigment contains zinc and titanium elements as impurities for barite. Prussian blue appears a permanent pigment that did not expose to vigorous light [29]. Blacking of yellow patches within the blue area refers to interaction of the yellow pigment with environmental conditions. 6 Yellow color Fig. 5. ATR-FTIR spectra of: (1) historical Sample “black color”; (2) gypsum; (3) lead white; (4) lamp black; (5) egg yolk; (6) shellac resin.
ATR-FTIR spectrum (Fig. 9) shows bands at 792, 711 and 667 cm1 that refer to iron oxide [35,36] and bands at 1020 and 873 cm1 that refer to aluminum silicate [17,37]. FESEM micrograph
76
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 7. ATR-FTIR spectra of: (1) historical sample “gray color”; (2) gypsum; (3) lead white; (4) lamp black (5) egg yolk; (6) shellac resin. Fig. 6. ATR-FTIR spectra of: (1) historical sample “brown color”; (2) gypsum; (3) lead white; (4) iron oxide “mars yellow”; (5) aluminum silicate “kaolin”; (6) egg yolk; (7) shellac resin.
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
77
Table 4 Relative concentration of amino acids of gray color and reference sample. Amino acid
Gray Color
Reference sample
Aspartic Acid Threonine Serine Glutamic Acid Proline Alanine Valine Leucine Tyrosine Phenylalanine Histidine Arginine Isoleucine Cystine Glycine Lysine Methionine
1.60 7.42 9.30 9.72 14.39 14.89 0.42 0.27 1.00 20.34 2.24 0.62 3.54 8.39 5.88 e e
5.06 3.38 5.10 39.44 2.05 7.97 4.28 7.57 2.74 6.43 2.45 7.65 e e e 4.90 0.98
(Fig. 2G) shows cluster of aluminosilicate crystals within groove of the paint film [45] and EDS microanalysis (Table 3) detects Fe, Al and Si elements [38], so it can be said that yellow pigment is yellow ochre. EDS microanalysis detects Ba, S and O elements of barite as extender with yellow ochre pigment, ATR-FTIR spectrum shows sulfate bands at 1110 cm1 [33,34]. Yellow pigment contains arsenic element as impurities. FESEM micrograph shows cracking of the paint film that attributes to presence of iron oxide and calcium salts, which promote light-induced oxidation [6,40e42]. 7 Gold color EDS microanalysis (Table 3) detects a high gold content alloy (Au 24.55 wt%) with trace amounts of copper (Cu 1.05 wt%) [12,46,47]. Gold color has no characteristic infrared bands (Fig. 10). FESEM micrograph (Fig. 2H) shows smooth gray surface with gaps that mean use of gilding technique in the painting.
4. Conclusion The study introduces more information about identity of the icon such as chemical composition of the icon layers, general state of the icon and impact of environmental conditions on the icon painting. The results obtained shows gypsum and lead white were used as ground materials in Saint Gregory Nazianzen Icon, Old Cairo. Lamp carbon black, brown ochre, Prussian blue, yellow ochre and gold were used as pigments. Egg yolk was used as binder of the paint layers. Shellac resin was used as varnish layer for the painting. Chemical composition of the pigments shows stability with the environmental conditions and it exhibits permanence of the paint colors, taking into account the effect of metal oxide and salts in promotion of light-induced oxidation for egg yolk binder and shellac varnish. The oxidation process leads to decreasing of the free amino acids of egg yolk binder, fading of the varnish glaze and cracking of the paint film. The identification of icon components will help the conservators to use the same materials used in the icon studied (ground, binder, pigments and varnish) in the gap filling of cracks, which were noticed by investigation of the surface morphology by scanning electron microscope. The analysis and investigations gave an indication that there is an oxidation mechanism for binder and varnish, and this means that preventive conservation especially light control should be applied by conservator for the icon studied.
Fig. 8. ATR-FTIR spectra of: (1) historical sample “blue color”; (2) gypsum; (3) lead white; (4) Prussian blue (5) egg yolk; (6) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
78
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 10. ATR-FTIR spectra of: (1) historical sample “gold color”; (2) gypsum; (3) lead white; (4) animal glue; (5) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 9. ATR-FTIR spectra of: (1) historical sample “blue color”; (2) gypsum; (3) lead white; (4) iron oxide “mars yellow”; (5) aluminum silicate “kaolin”; (6) egg yolk; (7) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Acknowledgment The authors would like to thank Dr. Wadea Malek (Ministry of Antiquities, Egypt) for his help during the collection of samples. References [1] http://www.coptic.net/EncyclopediaCoptica. [2] W.S. Taft, J.W. Mayer, The Science of Paintings, first ed., Springer Verlag, New York, USA, 2000. [3] B.H. Stuart, Analytical Techniques in Materials Conservation, first ed., John Wiley & Sons, Chichester, England, 2007. [4] Z. Goffer, Archaeological Chemistry, second ed., John Wiley & Sons, New Jersey, USA, 2007. [5] http://cameo.mfa.org. nech-Carbo , Anal. Chim. Acta 621 (2008) 109e139. [6] M.T. Dome [7] http://www.bio-rad.com. [8] G. Abdel-Maksoud, Y.M. Issa, M. Magdy, Int. J. Eng. Res. Gen. Sci. 3 (2015) 489e500. [9] C. Genestar, C. Pons, Anal. Bioanal. Chem. 382 (2005) 269e274. [10] D. Kovala-Demertzi, L. Papathanasis, R. Mazzeo, M.A. Demertzis, E.A. Varellac, S. Prati, J. Cult. Herit. 13 (2012) 107e113. , V.P. Martínez, J.V.G. Adelantado, F.B. Reig, M.C.M.M. Moreno, [11] M.T.D. Carbo J. Mol. Struct. 410e411 (1997) 559e563. nchez, A. Koutsoudis, M. Pamplona, [12] J.A. Stratis, C. Makarona, D. Lazidou, E.G. Sa R. Pauswein, G. Pavlidis, S. Simon, N. Tsirliganis, J. Cult. Herit. 15 (2012) 85e91. rez-Alonso, K. Castro, I. Martinez-Arkarazo, M. Angulo, M.A. Olazabal, [13] M. Pe J.M. Madariaga, Anal. Bioanal. Chem. 379 (2004) 42e50. , U. Casellato, E. Fiorin, P.A. Vigato, J. Cult. Herit. 5 (2004) 333e348. [14] D. Ajo , M. Ohlídalova , M. Novotna , I. Ne mec, Vib. Spec[15] E. Svobodov a, Z. Bos akova trosc. 63 (2012) 380e389. [16] R.J. Meilunas, J.G. Bentsen, A. Steinberg, IIC-Int. Inst. Conserv. 35 (1990) 33e51. [17] V. Ganitis, E. Pavlidou, F. Zorba, K.M. Paraskevopoulos, D. Bikiaris, J. Cult. Herit. 5 (2004) 349e360. [18] R. Mazzeo, S. Prati, M. Quaranta, E. Joseph, E. Kendix, M. Galeotti, Anal. Bioanal. Chem. 392 (2008) 65e76. [19] K.A. Dooley, S. Lomax, J.G. Zeibel, C. Miliani, P. Ricciardi, A. Hoenigswald, M. Loewb, J.K. Delaney, Analyst 138 (2013) 4838e4848. [20] G. Schmidt, M.J. Bessman, M.D. Hickey, S.J. Thannhauser, J. Biol. Chem. 223 (1956) 1027e1031. [21] T. Baird, S.E. Solomon, D.R. Tedstone, Br. Poult. Sci. 16 (1975) 201e208.
79
[22] C. Pelosi, G. Falletta, B.D. Dominicis, P. Baraldi, Procedia Chem. 8 (2013) 248e257. [23] S. Bruni, S. Caglio, V. Guglielmi, G. Poldi, Appl. Phys. A 92 (2008) 103e108. [24] M.R. Derrick, D. Stulik, J.M. Landry, Infrared Spectroscopy in Conservation Science, first ed., J. Paul Getty Trust, Los Angeles, USA, 1999. [25] S. Prati, G. Sciutto, R. Mazzeo, C. Torri, D. Fabbri, Anal. Bioanal. Chem. 399 (2011) 3081e3091. [26] M. Humphries, Fabric Reference, fourth ed., Prentice Hall, New Jersey, USA, 2008. [27] M.L. Ryder, T. Gabra-Sanders, Text. Hist. 16 (1985) 123e140. [28] G. Abdel-Maksoud, Z. Al-Saad, Mediterr. Archaeol. Archaeom. 9 (2009) 69e87. [29] Pigments through the Ages, http://www.webexhibits.org/pigments. [30] E. Tomasini, G. Siracusano, M.S. Maier, Microchem. J. 102 (2012) 28e37. [31] A. Bonneau, D.G. Pearce, A.M. Pollard, J. Archaeol. Sci. 39 (2012) 287e294. [32] L. Burgio, R.J.H. Clark, L. Sheldon, G.D. Smith, Anal. Chem. 77 (2005) 1261e1267. [33] S. Akyuz, T. Akyuz, G. Emre, A. Gulec, S. Basaran, Spectrochim. Acta A 89 (2012) 74e81. [34] P.L. Lang, C.D. Keefer, J.C. Juenemann, K.V. Tran, S.M. Peters, N.M. Huth, A.G. Joyaux, Microchem. J. 74 (2003) 33e46. [35] S. Vahur, A. Teearu, I. Leito, Spectrochim. Acta A 75 (2010) 1061e1072. [36] S. Vahur, U. Knuutinen, I. Leito, Spectrochim. Acta A 73 (2009) 764e771. [37] E. Pavlidou, M. Arapi, T. Zorba, M. Anastasiou, N. Civici, F. Stamati, K.M. Paraskevopoulos, Appl. Phys. 83 (2006) 709e717. [38] G.A. Mazzocchin, F. Agnoli, S. Mazzocchin, I. Colpo, Talanta 61 (2003) 565e572. [39] P. Seymour, The Artist's Handbook: a Complete Professional Guide to Materials and Techniques, first ed., Arcturus Publishing, London, United Kingdom, 2003. [40] C. Duce, L. Ghezzi, M. Onor, I. Bonaduce, M.P. Colombini, M.R. Tine, E. Bramanti, Anal. Bioanal. Chem. 402 (2012) 2183e2193. [41] L. Valianou, S. Wei, M.S. Mubarak, H. Farmakalidis, E. Rosenberg, S. Stassinopoulos, I. Karapanagiotis, J. Archaeol. Sci. 38 (2011) 246e254. [42] S.M. Halpine, IIC-Int. Inst. Conserv. 37 (1992) 22e38. [43] C. Miliani, B. Doherty, A. Daveri, A. Loesch, H. Ulbricht, B.G. Brunetti, A. Sgamellotti, Spectrochim. Acta A 73 (2009) 587e592. , G. Coccolini, S. Micheli, C. Lofrumento, M. Galeotti, A. Cagnini, [44] J. Striova E.M. Castellucci, Spectrochim. Acta A 73 (2009) 539e545. [45] A.E.D.C. Varajeao, I.R.J. Gilkes, R.D. Hart, Clay Clay Min. 49 (2001) 44e59. [46] M. Abdel-Ghani, B. Stern, H.G.M. Edwards, R. Janaway, Vib. Spectro. 62 (2012) 98e109. [47] A. Iordanidis, J. Garcia-Guinea, A. Strati, A. Gkimourtzina, Anal. Lett. 46 (2013) 936e945.
Contents lists available at ScienceDirect
Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc
Analytical study of Saint Gregory Nazianzen Icon, Old Cairo, Egypt Yousry M. Issa a, Gomaa Abdel-Maksoud b, *, Mina Magdy c a
Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt Conservation Department, Faculty of Archeology, Cairo University, Giza, 12613, Egypt c National Museum of Egyptian Civilization, Cairo, Egypt b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 May 2015 Received in revised form 2 July 2015 Accepted 3 July 2015 Available online 15 July 2015
The study aims to evaluate the state of icon through characterization of the icon layers (ground, paint and varnish layers) and to provide tools for assessment the impact of aging and environmental conditions in order to produce some solutions for conservation of the icon. Analytical techniques used in this study were attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscope-energy dispersive X ray spectroscopy (FESEM-EDX) and amino acid analyzer (AAA). The results obtained revealed that gypsum and lead white were used for ground layer. The identified pigments were lamp carbon black, brown ochre, Prussian blue, yellow ochre and gold leaf. Egg yolk was the binder used with most of pigments and animal glue was used with gold color. The varnish used was shellac resin. It was concluded that stable pigments gave permanent colors and environmental conditions had an influence on promotion of oxidation process. Auto-oxidation of binder and varnish materials occurred by the action of pigment components and light result in cracking of the paint film and fading of the varnish glaze. © 2015 Published by Elsevier B.V.
Keywords: Icon ATR-FTIR FESEM-EDX AAA Deterioration
1. Introduction Icons carry a lot of spiritual meaning in our lives. The art of icons presents symbolism of one or several events that carries a meaningful message [1]. The Icons are described as fruits of the Coptic art. Icons are composed of four layers: support, ground, paint “pigments and binder” and varnish layer. The support is the surface upon which the paint is applied [2]. The ground layer, also known as the primer or preparation layer, is the layer on which a drawing is made before the paint is applied [3]. The paint is a colored fluid preparation that is applied as a thin coating to the surface of solid materials. Generally, paint is mixture of at least three basic components: a pigment, a medium and a binder. Pigments are finely powdered solids used to impart color to other materials [4]. Medium, also known as vehicle or diluent, provides the material agent in which the other components of the paint are either dissolved or suspended [2,4]. Binder, also known as the binding medium or film former, is the component that binds the particles of pigment to each other and to the painted surface [4]. The varnish is a
* Corresponding author. E-mail addresses: [email protected] (Y.M. Issa), gomaaabdelmaksoud@ yahoo.com (G. Abdel-Maksoud), [email protected] (M. Magdy). http://dx.doi.org/10.1016/j.molstruc.2015.07.004 0022-2860/© 2015 Published by Elsevier B.V.
transparent material used to protect the paint layers and to provide the gloss of paint colors [3]. Deterioration of paintings is defined as a gradual decomposition of the chemical structure and physical integrity of the icon materials with time. This may be a result of environmental effects such as heat, sunlight, weathering, bacterial action, pollutants, or human activity [5]. Chemicals used in pigments can have a notable effect on binder and varnish materials because they promote lightinduced oxidation reactions [6]. Multi-techniques with high spatial resolutions are required for characterization of the icon layers and observation of the degradation products that associate with natural aging and concomitant effect of the environmental conditions. Attenuated total reflectionFourier transform infrared spectroscopy (ATR-FTIR) gives information about both organic and inorganic components in the paint and their degradation. Field emission scanning electron microscopy (FESEM) can be used for examination of the icon materials. The surface characteristics of painting can be investigated using electron imaging. Energy dispersive spectroscopy (EDS) gives information about elemental composition of the icon components. Amino acid analyzer (AAA) is used for identification of proteinaceous binding medium and observing the change of amino acids concentration [3]. The analysis and investigation used in this study will help the
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
71
conservator to make accurate conservation treatment especially in the process of completion of missed parts or in gap filling of cracks by using the same materials used in the icon components. They are also useful to determine the causes of deterioration forms, which help the conservators to make good preventive conservation (controlling of the surrounding environmental conditions such as light, temperature, relative humidity and etc.). The aim of present work is to analyze the icon layers (ground, paint and varnish layers) by multi-techniques in order to identify the chemical composition of icon materials and describe the influence of environmental conditions. After that, the conservator will have the ability to make very good plan for conservation of the icon. 1.1. Historical background Icon of Saint Gregory Nazianzen is located in church of Saint George, Monastery of Saint Mina (South of Cairo). The icon dates back to 18th century. It is believed to have been drawn by painter from school of Ibrahim El-Naseh and Yuhanna Al-Armani. 1.2. Icon description Icon of Saint Gregory Nazianzen (Fig. 1) is characterized by its bright colors and accurate implementation. Saint Gregory wears sticharion with blue color at upper part, red color at lower part and gray-color tailasan with crown on his head. The Saint Gregory also holds golden cross in his right hand and black stick in his left hand. There is a golden halo around his head. The Saint stands with yellow background. Name of Saint Gregory mentioned in the painting of icon with black color. The icon shows sever longitudinal and transversal fractures of the wood support. 2. Experimental data 2.1. Materials 2.1.1. Historical samples Seven micro samples were carefully taken from the fallen parts of damaged icon. The samples colors were white, black, brown, gray, blue, yellow and gold colors. The authors were not able to get sample from the support of icon. 2.1.2. Reference samples Seven fresh samples of ground (gypsum and lead white), binder (egg yolk and animal glue), pigments (lamp carbon, iron oxide “mars yellow”), varnish (shellac resin) and aluminum silicate (kaolin) materials were assembled and analyzed by ATR-FTIR method, while Prussian blue was obtained from library of Bio-Rad system [7]. Egg yolk reference sample was also analyzed by AAA method for comparison with the historical sample.
Fig. 1. Icon of Saint Gregory Nazianzen.
field emission scanning electron microscope (Quanta FEG-250, FEI Company, Hillsboro, Oregon, USA) equipped with EDX unit (Energy Dispersive X-ray Spectrophotometer, EDAX Apollo SDD, Mahwah, New Jersey, USA), with low-vacuum mode, accelerating voltage 20 kV, magnification 14 up to1,000,000 and resolution of 1 nm.
2.2. Methods 2.2.1. Attenuated total reflection Fourier transform infrared (ATRFTIR) spectroscopy Mid Infrared (MIR) spectra are recorded with a Vertex 70 FTIR spectrometer (Bruker Optics, Billerica Inc., Massachusetts, USA) equipped with a diamond ATR system. The spectra were acquired with 16 scans in the wavenumber range from 400 to 4000 cm1 and room temperature DLaTGS detector at 4 cm1 spectral resolution. 2.2.2. Field emission scanning electron microscopy-energy dispersive X-Ray spectroscopy (FESEM-EDX) Scanning electron microscopy (SEM) images were taken using
2.2.3. Amino acid analyzer (AAA) The chromatographic analysis of proteinaceous binder was carried on an LC 3000 amino acid analyzer (Eppendorf, Hamburg, Germany). The separation system comprised of a cooled compartment for autosampler, 4 buffer bottles, ninhydrin, washing solution, helium-inert gas manifold for the solutions, heating compartment for analytical column and derivatization-reactor, as well as twochannel photometric detection. The chromatographic separation was achieved with a cation exchange column BTC 2410-4 mm, 125 4 mm and lithium citrate buffer system. The device was controlled by WinLC combined with EZChrom data software. Samples were analyzed with 6 N HCl at 110 C in Teflon-capped
72
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Table 1 Infrared bands of the reference samples. Material
Band (cm1), (Assignment)
Gypsum [8] Lead White Prussian Blue Iron Oxide (Mars Yellow) Aluminum Silicate (Kaolin) Egg Yolk [8] Animal Glue Shellac Resin
2 3606, 3551 y(OeH), 1110, 1087, 1007 y(SO2 4 ), 658 d(SO4 ) 3344 y(OeH), 1642 d(OeH), 1033 y(CO2 3 ) 2082 y(C^N) 793, 711, 667 y(FeeO) 3689, 3649, 3620 y(OeH), 1026, 999 y(SieOeSi), y(SieOeAl), 910 y(AleOeH) 3282 y(NeH), 2923, 2853 y(CeH), 1744, 1633 y(C]O), 1541, 669 d(NeH), 1541 y(CeN), 1458, 1416, 1378 d(CeH) 2928, 2867 y(CeH), 1691 y(C]O), 1460, 1446, 1385 d(CeH) 3376 y(OeH), 2920, 2852 y(CeH), 1709, 1635 y(C]O), 1635 d(OeH), 1463, 1414, 1374 d(CeH), 1247, 1146, 1111, 1002, 943, 927 y(CeO)
vials for 24 h. After vacuum removal of HCl, the residue was dissolved in a lithium citrate buffer. 20 mL of the solution were loaded onto the cation exchange column, then four buffer system was applied with increased pH and it followed by post column reaction with ninhydrin. The ninhydrin flow rate was 0.2 mL/min at pressure of 0e50 bar. Detection carried out at 570 nm (Channel A) and in case of fault of detection or high concentration detection on a second channel (Channel B) at 470 nm.
3. Results and discussion Infrared bands of the historical samples (Table 1) will be compared to the bands of reference samples (Table 2). Energy dispersive X-ray spectroscopy (Table 3) detects the elemental composition of each paint color. Meanwhile, Scanning electron microscope (Fig. 2) gives images about the surface of paint colors. The study of paint layers of Saint Gregory Nazianzen by ATRFTIR, FESEM-EDX and AAA methods reveals that the ground material are gypsum and lead white, the binder is egg yolk, the varnish is shellac resin and animal glue is a binder agent for the bole leaf. Gypsum manifests ATR-FTIR bands at 3700e3399 cm1 y(OeH),
1649e1647 cm1 d(OeH), 1113e1110 cm1 y(SO2 and 4 ) 669e667 cm1 d(SO2 4 ) [9e11]. EDS microanalysis detects Ca, S and O elements which are characteristic of gypsum [12]. ATR-FTIR analysis exhibits lead white at 3700e3399 cm1 y(OeH), 1649e1647 cm1 d(OeH), 1429e1418 cm1 y(CO2 3 ) and 875e874 cm1 d(CO2 3 ) [11], [13e15]. EDS microanalysis detects Pb element which is characteristic of lead white [12]. FESEM micrograph shows bright particles of lead white. Egg yolk shows characteristic bands at 3402e3396 cm1 y(NeH), 2924e2849 cm1 y(CeH), 1732e1541 cm1 y(C]O), 1541, 669e667 cm1 d(NeH), 1541 cm1 y(CeN) and 1429e1324 cm1 d(CeH) [16e19]. EDS microanalysis detects P element as one component of egg yolk (phosphoprotein and phospholipid) [20] and ATR-FTIR spectrum exhibits phosphate band at 1030e1019 cm1 [21]. ATR-FTIR analysis exhibits bands for animal glue at 3396 cm1 y(NeH), 2919, 2852 cm1 y(CeH), 1620 cm1 y(C]O), 1541, 667 cm1 d(NeH) and 1418 cm1 d(CeH) [11,22,23]. Shellac resin is proved by appearance of ATR-FTIR bands at 3700e3399 cm1 y(OeH), 2924e2849 cm1 y(CeH), 1 1732e1620 cm y(C]O), 1649e1620 cm1 y(CeC),
Table 2 Infrared bands of the paint colors of historical samples. Color
Characteristic bands (cm1) in IR spectra
Material
White
3516, 1106, 1054, 667 3516, 1426, 874 3530, 3402, 1649, 1113 3530, 3402, 1649, 1429, 3402, 2924, 2853, 1649, 3530, 3402, 2924, 2853, 3700, 3530, 3399, 1647, 3700, 3530, 3399, 1647, 793, 669 3700, 3530, 3399, 1021, 3399, 2922, 2852, 1732, 3399, 2922, 2852, 1732, 3529, 3400, 1111, 669 3529, 3400, 1426, 875 3400, 2919, 2851, 1731, 3529, 3400, 2919, 2851, 3537, 3402, 1649, 1112, 3537, 3402, 1649, 1428, 2087 3402, 2922, 2852, 1730, 3537, 3403, 2922, 2852, 3396, 1648, 1110, 667 3396, 1648, 1422, 873 792, 711, 667 3396, 1020, 948, 873 3396, 2918, 2849, 1732, 3396, 2918, 2849, 1732, 3524, 1104, 667 3524, 1418, 873 3396, 2919, 2852, 1620, 3524, 3396, 2919, 2852,
Gypsum Lead White Gypsum Lead White Egg Yolk Shellac Resin Gypsum Lead White Iron Oxide Aluminum Silicate Egg Yolk Shellac Resin Gypsum Lead White Egg Yolk Shellac Resin Gypsum Lead White Prussian Blue Egg Yolk Shellac Resin Gypsum Lead White Iron Oxide Aluminum Silicate Egg Yolk Shellac Resin Gypsum Lead White Animal Glue Shellac Resin
Black
Brown
Gray
Blue
Yellow
Gold
874 1429, 1730, 1112, 1427,
1371 1649, 1429, 1371, 1231, 1113, 1020, 947 669 875
875 1647, 1622, 1541, 1427, 1372, 1324, 669 1647, 1622, 1427, 1372, 1324, 1233, 1112, 1021, 947
1620, 1426, 1372, 1324, 669 1731, 1620, 1426, 1372, 1324, 1234, 1111, 1019 669 874 1649, 1621, 1428, 1371, 669 1730, 1649, 1621, 1428, 1371, 1232, 1112, 1020, 947
1648, 1622, 1541, 1422, 1372, 667 1648, 1622, 1422, 1372, 1232, 1110, 1020, 948
1541, 1418, 667 1732, 1620, 1418, 1339, 1104
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79 Table 3 EDS microanalysis and elemental composition (atomic percentage) of each color of historical sample. Element
White
Black
Brown
Gray
Blue
Yellow
Gold
CK OK Na K Mg K Al K Ca K Si K SK Cl K KK PK Fe K Pb L Ba L Ti K Zn K Cr K As L NK Au L Cu K
38.30 49.69 0.45 0.36 0.55 4.55 0.98 4.34 0.52 e e 0.11 0.15 e e e e e e e e
62.14 25.82 e 0.44 0.74 1.18 0.82 1.69 1.66 0.18 0.21 e 0.32 1.36 e 0.40 2.34 e e e 0.70
59.63 30.80 0.83 0.35 3.62 0.93 0.83 e 1.29 0.25 0.41 0.14 0.84 e e e e e e 0.09 e
46.17 27.61 e 0.67 1.72 2.68 2.11 6.71 1.28 e e 0.55 e 8.28 e 2.23 e e e e e
47.77 32.34 0.29 0.15 1.15 1.88 1.71 4.83 0.87 0.24 0.21 0.29 0.61 2.22 3.87 1.58 e e e e e
58.58 29.54 1.05 e 1.13 2.77 0.93 2.22 0.91 0.26 0.18 0.32 e 1.76 e e e 0.36 e e e
48.71 7.47 e e 0.88 1.64 1.24 e e 0.18 e e e e e e e e 14.29 24.55 1.05
1429e1324 cm1 d(CeH) and 1324e947 cm1 y(CeO) [11,24,25]. All colors give the same chemical composition regarding the ground, the binder, and the varnish materials. 1 White color Fibers of paper appear within FESEM micrograph (Fig. 2A) as a flexible support for the paint layers and it is characteristic with ribbon-twisted structure that is remarkable to cotton fibers [26,27]. The fibers appear randomly with good distribution of the filler and the distance between fibers is very close [28]. There are tears due to the natural aging of fibers. In general, the state of most fibers is
73
good and this illustrates that area is a good climate for the icon with adjustment the environmental conditions. ATR-FTIR spectrum of (Fig. 3) shows characteristic bands of gypsum and lead white. EDS microanalysis (Fig. 4) detects Pb element of lead white and Ca, S and O elements of gypsum. FESEM micrograph (Fig. 2B) shows fracture crystals of calcium sulfate (gypsium), lead carbonate (lead white). White color shows that sample without paint and varnish layers. 2 Black color EDS microanalysis (Table 3) shows a high carbon content, which indicates the presence of carbon organic material. Carbon black has no characteristic infrared bands (Fig. 5). Carbon black is a common name for black pigment that made of plant materials or soot lamps [29]. FESEM micrograph (Fig. 2C) shows the paint surface is homogenous and smooth without globular particles or rough topography, so carbon black may be lamp black pigment [30e32]. Carbon black has a protecting influence against the light [5]. EDS microanalysis detects Ba, S and O elements of barite as extender with carbon black pigment, ATR-FTIR spectrum shows sulfate bands at 1113 cm1 [33,34]. Black pigment contains zinc element as impurities and copper element as contamination from palette's artist. A high amount of Chromium element may be attributed to contamination from artist's brush and this demonstrates usage of chromate pigment in painting of the icon and dates the icon to late 18th century or early 19th century. 3 Brown color EDS microanalysis (Table 3) did not detect Mn element so the use of umber and sienna pigments can be excluded. Brown color shows ATR-FTIR bands (Fig. 6) at 793 and 669 cm1 that refer to iron oxide [35,36] and bands at 1021 and 875 cm1 that refer to aluminum silicate [17,37]. FESEM micrograph (Fig. 2D) shows fracture of aluminosilicate crystals. EDS microanalysis detects Al,
Fig. 2. FESEM micrograph of historical samples: (A) paper support; (B) white color; (C) black color; (D) brown color; (E) gray color; (F) blue color; (G) yellow color; (H) gold color. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
74
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 3. ATR-FTIR spectra of: (1) historical sample “white color”; (2) gypsum; (3) Lead white.
Fig. 4. EDX spectrum and elemental composition of white color. (Representative Figure).
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
75
Fe, Si and O elements [37,38]. Ochre pigment is a natural pigment or synthetic iron oxide (Fe2O3) and kaolin clay (aluminum silicate, Al2Si2O5(OH)4) [29,39]. It can be concluded that brown pigment is ochre pigment (brown ochre). Brown color may be result of calcining the yellow ochre at certain temperature or mixing of yellow ochre with carbon black causing change the tone of the pigment to brown [37,39]. Brown pigment contains gold element as contamination from palette's artist. Presence of metal oxide and other salts have a role in promotion of light-induced oxidation for organic materials causing cracking of the paint film and fading of the varnish glaze [6,40e42]. Iron ions can form complexes with egg yolk protein, shellac resin and it acts as catalyst for oxidation of the binder and varnish materials. This assumption can be confirmed by presence of infrared bands of oxalate at 1622 and 1324 cm1 [14,43]. 4 Gray color Gray color may be a result of mixing white and black pigments. This assumption is confirmed by EDS microanalysis (Table 3) showing a high carbon content of carbon black pigment and a high percentage of calcium, silicon, aluminum, and oxygen elements of calcium sulfate and lead carbonate of white ground materials. ATRFTIR spectrum of gray color (Fig. 7) exhibits characteristic bands of gypsum and lead white of white pigment with no characteristic bands of carbon black pigment. FESEM micrograph (Fig. 2E) shows flakes of calcium sulfate and lead carbonate. EDS microanalysis detects Ba, S and O elements of barite as extender with the pigments, ATR-FTIR spectrum shows sulfate bands at 1111 cm1 [33,34]. Gray pigment contains zinc element as impurities for barite. Gray color shows fading of the varnish glaze due to presence of calcium salts, which promote light-induced oxidation [6,40e42]. Calcium salts of white pigment cause degradation of the egg yolk binder and shellac resin through association of Caþ2 ions with free carboxyl group of the organic materials producing calcium oxalate. This assumption can be confirmed by infrared bands of calcium oxalate at 1620 and 1324 cm1 [14,43]. Amino acid analysis of gray color (Table 4) exhibits distinctive concentration of amino acids: phenylalanine (20.34%), alanine (14.89%), proline (14.39%), glutamic acid (9.72%), serine (9.30%), cystine (8.39%), threonine (7.42%), glycine (5.88%), isoleucine (3.54%), histidine (2.24%), aspartic acid (1.60%), tyrosine (1.00%), arginine (0.62%), valine (0.42%) and leucine (0.27%). The results obtained shows that content of some amino acids of gray color are reduced (aspartic acid, glutamic acid, valine, leucine, tyrosine, histidine and arginine) or zeroed (lysine and methionine) as a result of oxidation process. 5 Blue color ATR-FTIR spectrum (Fig. 8) shows band at 2087 cm1, which is characteristic for Prussian blue [10,12,44]. FESEM micrograph (Fig. 2F) shows small particles of Prussian blue. EDS microanalysis detects Ba, S and O elements of barite as extender with Prussian blue pigment, ATR-FTIR spectrum shows sulfate bands at 1112 cm1 [33,34]. Blue pigment contains zinc and titanium elements as impurities for barite. Prussian blue appears a permanent pigment that did not expose to vigorous light [29]. Blacking of yellow patches within the blue area refers to interaction of the yellow pigment with environmental conditions. 6 Yellow color Fig. 5. ATR-FTIR spectra of: (1) historical Sample “black color”; (2) gypsum; (3) lead white; (4) lamp black; (5) egg yolk; (6) shellac resin.
ATR-FTIR spectrum (Fig. 9) shows bands at 792, 711 and 667 cm1 that refer to iron oxide [35,36] and bands at 1020 and 873 cm1 that refer to aluminum silicate [17,37]. FESEM micrograph
76
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 7. ATR-FTIR spectra of: (1) historical sample “gray color”; (2) gypsum; (3) lead white; (4) lamp black (5) egg yolk; (6) shellac resin. Fig. 6. ATR-FTIR spectra of: (1) historical sample “brown color”; (2) gypsum; (3) lead white; (4) iron oxide “mars yellow”; (5) aluminum silicate “kaolin”; (6) egg yolk; (7) shellac resin.
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
77
Table 4 Relative concentration of amino acids of gray color and reference sample. Amino acid
Gray Color
Reference sample
Aspartic Acid Threonine Serine Glutamic Acid Proline Alanine Valine Leucine Tyrosine Phenylalanine Histidine Arginine Isoleucine Cystine Glycine Lysine Methionine
1.60 7.42 9.30 9.72 14.39 14.89 0.42 0.27 1.00 20.34 2.24 0.62 3.54 8.39 5.88 e e
5.06 3.38 5.10 39.44 2.05 7.97 4.28 7.57 2.74 6.43 2.45 7.65 e e e 4.90 0.98
(Fig. 2G) shows cluster of aluminosilicate crystals within groove of the paint film [45] and EDS microanalysis (Table 3) detects Fe, Al and Si elements [38], so it can be said that yellow pigment is yellow ochre. EDS microanalysis detects Ba, S and O elements of barite as extender with yellow ochre pigment, ATR-FTIR spectrum shows sulfate bands at 1110 cm1 [33,34]. Yellow pigment contains arsenic element as impurities. FESEM micrograph shows cracking of the paint film that attributes to presence of iron oxide and calcium salts, which promote light-induced oxidation [6,40e42]. 7 Gold color EDS microanalysis (Table 3) detects a high gold content alloy (Au 24.55 wt%) with trace amounts of copper (Cu 1.05 wt%) [12,46,47]. Gold color has no characteristic infrared bands (Fig. 10). FESEM micrograph (Fig. 2H) shows smooth gray surface with gaps that mean use of gilding technique in the painting.
4. Conclusion The study introduces more information about identity of the icon such as chemical composition of the icon layers, general state of the icon and impact of environmental conditions on the icon painting. The results obtained shows gypsum and lead white were used as ground materials in Saint Gregory Nazianzen Icon, Old Cairo. Lamp carbon black, brown ochre, Prussian blue, yellow ochre and gold were used as pigments. Egg yolk was used as binder of the paint layers. Shellac resin was used as varnish layer for the painting. Chemical composition of the pigments shows stability with the environmental conditions and it exhibits permanence of the paint colors, taking into account the effect of metal oxide and salts in promotion of light-induced oxidation for egg yolk binder and shellac varnish. The oxidation process leads to decreasing of the free amino acids of egg yolk binder, fading of the varnish glaze and cracking of the paint film. The identification of icon components will help the conservators to use the same materials used in the icon studied (ground, binder, pigments and varnish) in the gap filling of cracks, which were noticed by investigation of the surface morphology by scanning electron microscope. The analysis and investigations gave an indication that there is an oxidation mechanism for binder and varnish, and this means that preventive conservation especially light control should be applied by conservator for the icon studied.
Fig. 8. ATR-FTIR spectra of: (1) historical sample “blue color”; (2) gypsum; (3) lead white; (4) Prussian blue (5) egg yolk; (6) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
78
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Fig. 10. ATR-FTIR spectra of: (1) historical sample “gold color”; (2) gypsum; (3) lead white; (4) animal glue; (5) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 9. ATR-FTIR spectra of: (1) historical sample “blue color”; (2) gypsum; (3) lead white; (4) iron oxide “mars yellow”; (5) aluminum silicate “kaolin”; (6) egg yolk; (7) shellac resin. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Y.M. Issa et al. / Journal of Molecular Structure 1100 (2015) 70e79
Acknowledgment The authors would like to thank Dr. Wadea Malek (Ministry of Antiquities, Egypt) for his help during the collection of samples. References [1] http://www.coptic.net/EncyclopediaCoptica. [2] W.S. Taft, J.W. Mayer, The Science of Paintings, first ed., Springer Verlag, New York, USA, 2000. [3] B.H. Stuart, Analytical Techniques in Materials Conservation, first ed., John Wiley & Sons, Chichester, England, 2007. [4] Z. Goffer, Archaeological Chemistry, second ed., John Wiley & Sons, New Jersey, USA, 2007. [5] http://cameo.mfa.org. nech-Carbo , Anal. Chim. Acta 621 (2008) 109e139. [6] M.T. Dome [7] http://www.bio-rad.com. [8] G. Abdel-Maksoud, Y.M. Issa, M. Magdy, Int. J. Eng. Res. Gen. Sci. 3 (2015) 489e500. [9] C. Genestar, C. Pons, Anal. Bioanal. Chem. 382 (2005) 269e274. [10] D. Kovala-Demertzi, L. Papathanasis, R. Mazzeo, M.A. Demertzis, E.A. Varellac, S. Prati, J. Cult. Herit. 13 (2012) 107e113. , V.P. Martínez, J.V.G. Adelantado, F.B. Reig, M.C.M.M. Moreno, [11] M.T.D. Carbo J. Mol. Struct. 410e411 (1997) 559e563. nchez, A. Koutsoudis, M. Pamplona, [12] J.A. Stratis, C. Makarona, D. Lazidou, E.G. Sa R. Pauswein, G. Pavlidis, S. Simon, N. Tsirliganis, J. Cult. Herit. 15 (2012) 85e91. rez-Alonso, K. Castro, I. Martinez-Arkarazo, M. Angulo, M.A. Olazabal, [13] M. Pe J.M. Madariaga, Anal. Bioanal. Chem. 379 (2004) 42e50. , U. Casellato, E. Fiorin, P.A. Vigato, J. Cult. Herit. 5 (2004) 333e348. [14] D. Ajo , M. Ohlídalova , M. Novotna , I. Ne mec, Vib. Spec[15] E. Svobodov a, Z. Bos akova trosc. 63 (2012) 380e389. [16] R.J. Meilunas, J.G. Bentsen, A. Steinberg, IIC-Int. Inst. Conserv. 35 (1990) 33e51. [17] V. Ganitis, E. Pavlidou, F. Zorba, K.M. Paraskevopoulos, D. Bikiaris, J. Cult. Herit. 5 (2004) 349e360. [18] R. Mazzeo, S. Prati, M. Quaranta, E. Joseph, E. Kendix, M. Galeotti, Anal. Bioanal. Chem. 392 (2008) 65e76. [19] K.A. Dooley, S. Lomax, J.G. Zeibel, C. Miliani, P. Ricciardi, A. Hoenigswald, M. Loewb, J.K. Delaney, Analyst 138 (2013) 4838e4848. [20] G. Schmidt, M.J. Bessman, M.D. Hickey, S.J. Thannhauser, J. Biol. Chem. 223 (1956) 1027e1031. [21] T. Baird, S.E. Solomon, D.R. Tedstone, Br. Poult. Sci. 16 (1975) 201e208.
79
[22] C. Pelosi, G. Falletta, B.D. Dominicis, P. Baraldi, Procedia Chem. 8 (2013) 248e257. [23] S. Bruni, S. Caglio, V. Guglielmi, G. Poldi, Appl. Phys. A 92 (2008) 103e108. [24] M.R. Derrick, D. Stulik, J.M. Landry, Infrared Spectroscopy in Conservation Science, first ed., J. Paul Getty Trust, Los Angeles, USA, 1999. [25] S. Prati, G. Sciutto, R. Mazzeo, C. Torri, D. Fabbri, Anal. Bioanal. Chem. 399 (2011) 3081e3091. [26] M. Humphries, Fabric Reference, fourth ed., Prentice Hall, New Jersey, USA, 2008. [27] M.L. Ryder, T. Gabra-Sanders, Text. Hist. 16 (1985) 123e140. [28] G. Abdel-Maksoud, Z. Al-Saad, Mediterr. Archaeol. Archaeom. 9 (2009) 69e87. [29] Pigments through the Ages, http://www.webexhibits.org/pigments. [30] E. Tomasini, G. Siracusano, M.S. Maier, Microchem. J. 102 (2012) 28e37. [31] A. Bonneau, D.G. Pearce, A.M. Pollard, J. Archaeol. Sci. 39 (2012) 287e294. [32] L. Burgio, R.J.H. Clark, L. Sheldon, G.D. Smith, Anal. Chem. 77 (2005) 1261e1267. [33] S. Akyuz, T. Akyuz, G. Emre, A. Gulec, S. Basaran, Spectrochim. Acta A 89 (2012) 74e81. [34] P.L. Lang, C.D. Keefer, J.C. Juenemann, K.V. Tran, S.M. Peters, N.M. Huth, A.G. Joyaux, Microchem. J. 74 (2003) 33e46. [35] S. Vahur, A. Teearu, I. Leito, Spectrochim. Acta A 75 (2010) 1061e1072. [36] S. Vahur, U. Knuutinen, I. Leito, Spectrochim. Acta A 73 (2009) 764e771. [37] E. Pavlidou, M. Arapi, T. Zorba, M. Anastasiou, N. Civici, F. Stamati, K.M. Paraskevopoulos, Appl. Phys. 83 (2006) 709e717. [38] G.A. Mazzocchin, F. Agnoli, S. Mazzocchin, I. Colpo, Talanta 61 (2003) 565e572. [39] P. Seymour, The Artist's Handbook: a Complete Professional Guide to Materials and Techniques, first ed., Arcturus Publishing, London, United Kingdom, 2003. [40] C. Duce, L. Ghezzi, M. Onor, I. Bonaduce, M.P. Colombini, M.R. Tine, E. Bramanti, Anal. Bioanal. Chem. 402 (2012) 2183e2193. [41] L. Valianou, S. Wei, M.S. Mubarak, H. Farmakalidis, E. Rosenberg, S. Stassinopoulos, I. Karapanagiotis, J. Archaeol. Sci. 38 (2011) 246e254. [42] S.M. Halpine, IIC-Int. Inst. Conserv. 37 (1992) 22e38. [43] C. Miliani, B. Doherty, A. Daveri, A. Loesch, H. Ulbricht, B.G. Brunetti, A. Sgamellotti, Spectrochim. Acta A 73 (2009) 587e592. , G. Coccolini, S. Micheli, C. Lofrumento, M. Galeotti, A. Cagnini, [44] J. Striova E.M. Castellucci, Spectrochim. Acta A 73 (2009) 539e545. [45] A.E.D.C. Varajeao, I.R.J. Gilkes, R.D. Hart, Clay Clay Min. 49 (2001) 44e59. [46] M. Abdel-Ghani, B. Stern, H.G.M. Edwards, R. Janaway, Vib. Spectro. 62 (2012) 98e109. [47] A. Iordanidis, J. Garcia-Guinea, A. Strati, A. Gkimourtzina, Anal. Lett. 46 (2013) 936e945.