Polychrome arhat figures dated from the Song Dynasty (960–1279 CE) at the Lingyan Temple, Changqing, Shandong, China

Abstract

Scientific analysis revealed the materials and techniques used in the process of making polychrome sculptures providing a solid foundation for the protection and restoration of the painted statues. In addition, the analyses revealed changes in colour schemes applied to the sculptures can provide the basis for the virtual restoration of the painted statues. In order to carry out scientifically-informed protection and restoration of the Bodhidharma statue from the Lingyan Temple, Changqinq, Shandong, several analytical methods such as optical microscope (OM), Micro-Raman spectroscopy (μ-RS), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDS) and Fourier transform infrared spectroscopy (FTIR) were employed. Analyses clearly reveal the information including the stratigraphic structure and the composition of pigment. The use of silver foils and golden yellow pyrophyllite mineral to replace gold foils were found in the gilding paint layer in the later repainting after the Song Dynasty. This work reports the coexistence of emerald green (Cu(C₂H₃O₂)₂·3Cu(AsO₂)₂) and the degradation product lavendulan (NaCaCu₅(AsO₄)₄Cl·5H₂O) in large areas of the paint stratigraphy and on the surface confirming that the degradation of emerald green is related to the thickness of the paint layer; in thinner paint layers emerald green is transformed in lavendulan, while thicker layers of contain both lavendulan and emerald green, suggesting an environmental source of chlorides.