Multi-analytical investigations on a tomb mural painting of the Yuan dynasty in Chongqing, China

In this study, we conducted diagnostic research on a precious Yuan dynasty tomb mural painting (A.D.1271–1368) excavated in Chongqing, 2005. To restore the painting, the painting technique and the artwork's preservation state were investigated through optical microscope (OM), portable X-ray fluorescence (p-XRF), micro-Raman spectroscopy (μ-Raman), macro-Fourier transform infrared spectroscopy (macro-FTIR), and X-ray powder diffraction (XRD) analyses. During this process, the coarse ground, fine ground and painting layer were characterized and analyzed. Experimental results show that the compositions of coarse ground are calcite and soil, while fine ground mainly consists of calcite and a few amounts of silicate. We also investigated and identified the pigments and binders used for the painting layers, which revealed that carbon black was used for the black pigment, cinnabar, red ochre and small amounts of red lead were used for the red pigments. To further investigate the distribution of materials in cross-sections with special attention to trace presented organic material, a FPA detector was used for imaging coupled with a large radius germanium crystal equipped attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. It has been found that the protein may be used as the binder and organic additive in mural painting. Our work enhances the understanding of the mural painting technique of the Yuan dynasty and also provides a reference for the future restoration work of paintings.