| The conservation of terra cotta of Qin dynasty is the research focus in this area since 1970s. The main conservation problems of terra cotta are crumbling and fading of the color. The color layer is consist of two main parts, pigments and binders. The pigments are the most important part, and higher contents in the lay. Although the binders is lower than pigments in contents, they are very important for the strength and stable of the layer. Almost all conservation problems of color layer are relevant to those two parts. So the analysis of pigments and binders of color layer is the base of terra cotta conservation.The samples are taken in the archaeology sites. And the pigments are analyzed by the means of polarized light microscopy, laser Raman microscopy spectrometry, X ray fluorescence spectrometry and X ray diffraction spectrometry. The Cinnabar, Malachite, Azurite, Hydrocerussite and Apatite are identified in the color layers of terra cotta. The mixture of two kinds of pigments, Cinnabar and Hydrocerussite, Minium and Apatite, and the mixture of three pigments, Cinnabar, Minium and Han Purple, Cinnabar, Hydrocerussite and Apatite, are identified too in the layers.The binders in color layers are studied by the means of gas chromatography-mass spectrometry. The contents of amino acids, fatty acids and polysaccharide in the binders are analyzed and calculated. It can be seen that the unstable situation of terra cotta color layers are due to the low contents of binders from the results of calculation. The principal contents analysis (PCA), a kind of statistics method, is used in proceeding the data of analysis. In PCA, the data can be clustered in the mixture of animal glue and egg, or animal glue and casein in PCA results. So binders in the terra cotta color layers can be identified as two kinds of mixture. And from the analysis results, it can be concluded that there are no fatty acids or polysaccharide binders in the color layers of terra cotta. |
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