Scientific Examination of Mosaic and Mural Painting in Third Millennium BC in Iran

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1 Proceedings of the 39 th International Symposium for Archaeometry, Leuven (2012) Scientific Examination of Mosaic and Mural Painting in Third Millennium BC in Iran R. Bahadori 1, F. Bahrololoumi 1 and S. H. Ahmadi 2 1. Research centre for conservation of cultural relics, Tehran, Iran, bahadoriroya@yahoo.com, R.bahadori@richt.ir, bfaranak@yahoo.com 2. Chemistry & Chemical Engineering Research Centre of Iran, ahmadi@ccerci.ac.ir ABSTRACT Colours have always played an important role in improving the quality of our environment. Many of the artefacts that we store in the museums are decorated with a wide variety of different dyes and pigments. The fragments of mural paintings in Malian (Fars, south of Iran), mural paintings and mosaics at the archaeological sites of Shahdad in Kerman (east of Iran) and Tappeh Zaghe (Ghazvin plain, central of Iran) were analyzed in this work. All of these paintings belong to 3 rd millennium BC in Iran. Polarized light microscopy (PLM), X-ray diffraction (XRD), scanning electron microscopy in combination with energy dispersive X-ray (SEM-EDX) microanalysis and Fourier transform infrared (FTIR) spectroscopy were used for the characterization of the structure of the painting layers of samples taken from mural paintings and mosaics. According to the obtained results, red and yellow ochres, charcoal black and calcium were detected as red, yellow, black and white pigments in Malian painting, respectively. Calcium, dolomite, quartz and clay were also identified in plaster layer of this painting. In the Shahdad painting, a mixture of calcium and quartz were used as the white colour. Red, blue and white stones mounted on mosaics from Shahdad were identified as red ochre, azurite and calcium, respectively. The black material used as adhesive for pasting the mosaic, includes calcium, dolomite and an organic material. The red and yellow colours as traces in Tappe Zaghe were red and yellow ochres respectively, and the white colour was a mixture of quartz and calcium. KEYWORDS Iran, Mural Painting, Pigment, Third Millennium BC. Introduction Identifying the pigments used in various historical eras and understanding the methods of preparation and processing are considered as the important indices in studying the level of technological improvement at any era. Notwithstanding the lack of, or limited, written sources in this field, the type of applied pigments and their preparation methods may be investigated based on instrumental analysis of archaeological artefacts. Such information may also be used to regenerate the cultural behaviour of the humans in the societies and various establishments. Additionally, the prehistoric trade relationships among the tribes established in regions may be investigated by following up and determining the origin of the ingredients. In this article, the pigments and plaster layer used in mural paintings from the archaeological site of Malian (in Fars, Iran), mural painting and mosaics of the archaeological site of Shahdad (Kerman, Iran) and traces of paint layers in Tapeh Zagheh (Ghazvin, Iran) belonging to the 3 rd millennium B.C. were analytically studied and their ingredients were identified. Methodology There are a variety of methods used to study ancient pigments and mural paintings, the most suitable method may be chosen depending on the type and amount of the sample (Stuart, 2007). Considering the low quantity of the sample and limitations of the available analytical methods, certain methods were used which would be as non-destructive as possible or at least require the least amount of the sample. After sampling the colours (if any), all of them were studied by using polarized light microscopy (PLM). In order to do so, a part of each sample was mounted using a suitable resin and prepared for microscopic studies. Cross sections were recorded with a James Swift system metallurgical microscope. For the identification of pigment composition, the samples were investigated with wet chemical methods. This study included the effect of acid, alkaline and other chemical agents on the samples. This is a simple low-cost method and gives good information regarding the identification of pigments. Chemical methods shall be ignored and replaced by instrumental methods in microsamples. Scanning electron microscopy in combination with energy dispersive X-ray (SEM-EDX) was used for elemental microanalysis of the samples. This technique requires a small amount of the sample without sample preparation. A Tescan (Brno, Czech) scanning electron microscope equipped with energy dispersive X-ray microanalysis system was used in this work. In order to identify the composition of the samples, the X-ray Diffraction (XRD) method was used. Finely powdered sample was used for coating the lamella. The used instrument was a Seifert 19

2 (Frankfurt, Germany) 3000T2T X-ray diffractometer with copper tube (40kV, 30mA). The diffraction of powdered samples was measured from 5-80 degrees, within 0.02 intervals with 0.4 sec steps. Organic and some mineral pigments, varnish and plaster layers, were studied by Fourier Transform Infrared spectroscopy. For preparation, some micrograms of the sample are ground inside an agate mortar with times dried potassium bromide (KBr) and this is then compressed into a transparent disc (THK= 1mm) under high pressure in vacuum conditions. The spectra were recorded by a Shimadzu (Tokyo, Japan) IR Prestige spectrometer. Discussion Identification of pigments used in the mural paintings of Malian, Fars One set of the most ancient mural paintings discovered in Iran are those of Malian, Fars. The ancient Malian tall in Beyza Plain, western Fars, is located at a distance of roughly 36km from the northwest of Shiraz. The excavations in Malian indicate that this site was habitable from the late 4 th millennium to the late 3 rd millennium B.C. During the excavations in the 70 s by Sumner, certain mural paintings were discovered, some of which are now kept in the storage rooms of national museum of Iran (Sumner, 1975). Red, yellow, white and black colours were sampled from the paintings in order to identify the pigments (Fig. 1A). Results of the analysis showed that red and yellow pigments use red and yellow ochres (Fe 2 O 3 ), black and white pigments use charcoal black and calcium (CaCO 3 ) and the plaster layer of the paintings uses calcium, dolomite (CaMg(CO 3 ) 2 ), quartz (SiO 2 ) and clay minerals. EDX analyses of the red layer in cross section (Fig. 1B) and yellow colour, confirm red and yellow ochres respectively, which is in agreement with the presence of higher contents of iron (Fig. 2). "# Fig. 1. A) The fragments of mural painting in Malian B) microscopic image of the cross section of red colour, 50x. Fig. 2. EDX analysis of the yellow colour in the M2 sample. Identification of mural painting and mosaics from Shahdad, Kerman Shahdad archaeological site with the ancient name Khabis is located at the western margin of the Lout desert within a 4km distance from the current city of Shahdad. Certain samples of superficial potteries were found at the eastern side of this site by the research group of the geographical institute of Tehran university in The archaeological department of Lout desert managed to discover prehistoric civilizations from the 4 th and 3 rd millenniums B.C. during several seasons of excavation, and found valuable objects and artefacts such as pottery, stone, metal, painting, mat, small statues and cloth items. The image of a man sitting in front of a palm which was painted using red, white and black pigments is one of these artefacts (Catalogue of Lout desert Exhibition, 1972). A design of this painting has been given in Fig. 3 and the location of the sampling to determine the type of pigments has been given in Fig. 4 (Hakemi, 1997). Fig. 3. Design of mural painting of Shahdad. 20

3 The results of analysis of this painting indicate that red pigment includes calcium ; however, the elemental analysis results do not indicate the existence of any element which could be used for the red colour. This may be due to the light colour of the pigment. The white pigment and plaster layer includes a mixture of calcium and quartz. XRD showed that the grey support layer was a mixture of quartz and calcium. Fig. 4. The fragment of mural painting in Shahdad. Another object found in this region is a piece of mosaic decorated by tiny parts of stone in white, green and red colours. A design of this mosaic and the parts of stone taken from the same are shown in Fig. 5 and 6 respectively. These stones, which have been regularly cut, have rough dimensions of 0.1 x 0.1 x 0.1mm. This mosaic is now kept in the Iranian national museum. Fig. 5. Design of a mosaic in Shahdad. A B Fig. 6. A) Red, green and white stones used in the mosaic of Shahdad and B) Green stones change to blue when was crushed. The stone pieces installed on the mosaic were analyzed after being powdered. Red colour stone pieces included traces of iron. The microscopic study under polarized light indicated that the red stone is red ochre (Fig. 7). The white pieces were calcium. The green colour pieces became blue after being powdered (Fig. 6B) and it was known that the respective outer surface was blue first. These stone pieces were azurite (2CuCO 3. Cu(OH) 2 ) and calcite (Fig. 8). Conversion of azurite to green malachite is a recognized phenomenon due to the environmental agents (Rapp, 2009). Certain effects of an oily black material was seen at the outer sides which was identified as an organic oily substance using the FTIR method. An absorption band at 1730cm -1 was attributed to oil in the FTIR spectrum. "# Fig. 7. Photomicrograph of the red stone of shahdad, 10x, A) in polarized light B) in reflected light. Fig. 8. XRD spectrum of the green stones in the mosaic of shahdad. 21

4 Identification of traces of paint layers at Tappeh Zagheh, Ghazvin Tappeh Zagheh is located approximately 60km south of Ghazvin city and roughly 8km northeast of Sagezabad village in the region of Bolouk Zahra on the Ghazvin Plain. Ghazvin plain is located at a rough height of 1,100m from the surface of the free seas, north of the Alborz mountains and east of the Zagros Mountains. The archaeological site of Tepe Zaghe together with Tepe Ghabrestan and Sagezabad have been under excavation since 1970 by the excavation boards of the archaeology group and archaeological institute of Tehran university. The history of Tappeh Zaghe dates back to the 5 th millennium B.C. (Negahban, 1972). A variety of works, such as different pottery, metal works and certain traces of paint layers on the floors and walls were found during the archaeological excavations of In order to identify these, red, yellow and white colours were sampled (Fig. 9). The results of the chemical analysis of the colour samples applied to the paint works of Tappeh Zaghe indicate that the red and yellow pigments used in these paintings include or ochre. The white pigment contains a mixture of quartz and calcium and its plaster layer includes quartz, clay minerals and calcium. The results of three various analytical methods completely confirm each other. The EDX results of the red colour have been presented in Fig. 10 and these indicate the existence of iron compounds. of calcium, quartz and clay mineral. It is emphasized that in these samples there was no gypsum in the support layers and the paintings were made on limestone. Transforming blue coloured azurite to green coloured malachite in the stones mounted on the mosaic of Shahdad is of a considerable point in this study. Fig. 10. EDX analysis corresponding to T1. Fig. 9. Traces of red and yellow coluor from the Tappeh Zaghe painting in Ghazvin. The results of different analysis methods of colours of three painting and stone pieces mounted on the mosaic have been given in Table 1. Conclusion In this study, 13 samples of coloured and stone pieces mounted on the mosaic were analyzed. These samples belonged to the archaeological sites of Malian, Shahdad and Tappeh Zaghe from the layers attributed to the 3 rd millennium B.C. In order to analyze these samples, chemical, analytical and instrumental methods including wet chemistry, OM, XRD, FTIR and SEM-EDX were used. The first three methods mentioned were used for compound analysis while the fourth method was applied for elemental analysis. In these paintings, organic substances were used as binding material or varnishes. These results indicate that the pigments used in the 3 rd millennium B.C. paintings include calcium or limestone, yellow and red ochre and azurite. The plaster layer on which the pigment layer is applied used is a mixture 22

5 Table 1. The result of Identification of samples. Name of sample Locatio n Type&color of sample M1 Malian Red color M2 Malian Yellow color EDX analysis Cross section: Fe,Ca,Si Fe, Si, Ca Mg, Al XRD analysis, Calcite,, Dolomite, Ochre C alcite, Dolomite,, Other analysis PLM:, calcium PLM: ochre, limestone Identification Pigment: iron oxide plaster layer: calcium, Dolomite,, clay M3 Malian Black color Si, Ca, Fe, Mg, Al, M4 Malian White color - S1 Shahdad Red color (painting) S2 Shahdad White color (painting) S3 Shahdad Red Stone S4 Shahdad Green Stone S5 Shahdad White Stone Black S6 Shahdad Adhesive (between mosaic) T1 Tappeh Zaghe Red color Ca, Na, Si, Mg Dolomite, Calcite, Calcite, Dolomite, Calcite, - Calcite, PLM: Charcoal black,, PLM; calcium, Ca, Fe Calcite PLM: Charcoal black calcium Pigmentplaster layer: calcium, calcium, Ochre, calcium - Azurite, - Azurite, - Calcite - - Si, Ca, Al, Fe, K, Mg, Calcite,, Clay minerals FTIR: Calcite,, Organic material - calcium Organic material Pigment: Ochre plaster layer:, clay, calcium T2 Tappeh Zaghe Yellow color Ca, Si, P, Al, Fe, K, Mg,, Calcite - Yellow ochre Acknowledgments The authors would like to thank Seyed Iraj Beheshti of the petrography department of the Research Centre of Cultural Relics for the microscopic examination. References Hakemi, A. 1997, Shahdad, Archaeological Excavation of the Bronze Age Center in Iran, Ismeo, Rom. Rapp, G. R. 2009, Archaeomineralogy, Springer, Berlin. Stuart, B. 2007, Analytical Techniques in Material Conservation, John Wiley and Sons. Sumner, W. M. 1975, Excavation at tale Malyn: A summary of three season results, in: Proceedings of the IIIRD annual symposium on archaeological research in Iran, Ed: Bagherzade, F., Iranian Center for Archaeological Research, Negahban, E. 1972, Reports of the Excavation in Archaeological Sites Sagzabad in Ghazvin Plain, Marlik, Tehran University (in Farsi). Catalogue of Dashte Loute Exhibition, 1971, Iran Bastan Museum. 23