Multi-analysis technique researches the painting materials and technics of polychrome arhat statue in Lingyan Temple, Shandong Province, China

The Arhat statues of the Thousand Buddha Hall in Lingyan Temple, located in Shandong Province, is renowned as “the first masterpiece of sculpture in China” and possess significant artistic value. The integration of diverse analytical techniques to uncover the material composition, manufacturing process, state of preservation, and artistic significance of the statue holds great importance for the scientific protection and restoration of cultural artifacts in the future, while also serving as a foundation for virtual restoration. In this research, X-ray inspection, ultra-depth-of-field optical microscopy (OM), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDS), and micro-Raman spectroscopy (µ-RS) were employed for the analysis and examination of the statue of “Niushi Bhikshu (牛呞比丘尊者)” in Lingyan Temple. The X-ray examination revealed valuable insights into the internal structure and preservation status of the statue. Discovery of copper coin inside the statue offers a new material for studying Buddha statue Zhuangzang (装藏). Analysis of the painted layers reveals that the statue has undergone at least eight instances of painting throughout its history. The mineral pigments used in the polychrome are red lead, cinnabar, hematite, chalk, cerusite, hydrocerussite, Emerald green (Cu(C₂H₃O₂)₂·3Cu(AsO₂)₂, synthetic), ultramarine (synthetic), carbon black and so on. It was found that Emerald green was used with ultramarine and chalk, and the former was completely transformed into Lavendulan (NaCaCu₅(AsO₄)₄Cl·5H₂O). This represents the first known instance of emerald green being mixed with ultramarine and chalk, resulting in a complete transformation into lavendulan. Indicating that the qualitative change of Emerald green is closely associated with its microenvironment. The differences in Raman spectra between cerusite (PbCO₃) and hydrocerussite (2PbCO₃·Pb(OH)₂) of lead white pigment are pointed out. Silver foil layers and golden clay coating layers were found in the gilding painted layer, in which the silver foils had been corroded and transformed into silver sulfide. The use of silver foils and golden mineral pigment instead of gold foils to decorate the statue enriched the understanding of the gilding decoration technology of the ancient Chinese polychrome statue. This study enhances the scientific research content related to the arhat statues in Lingyan Temple. It brings new perspectives or new materials to research of Buddha statue Zhuangzang, corrosion of emerald green pigment, special application of lead white, and gilding decoration technology, etc. At the same time, it offers a scientific foundation for the protection and restoration of these statues. Additionally, analysis of painting materials provides essential information for the virtual restoration of the color texture of the statues.