Degradation of emerald green: scientific studies on multi-polychrome Vairocana Statue in Dazu Rock Carvings, Chongqing, China

Scientists have identified lavendulan and mimetite as degradation products of emerald green and cerussite pigments in the multi-polychrome Vairocana Statue at Dazu Rock Carvings. These secondary compounds form through complex chemical processes involving arsenic oxidation, ion migration, and precipitation under high humidity and soluble salt conditions. The study employed optical microscopy, Raman spectroscopy, SEM-EDS, and pigment layer analysis to reveal that the statue's paintings were executed at least four times, with the most recent likely occurring after 1850s. This discovery highlights the significance of emerald green degradation in heritage conservation and provides insights into the characterization of copper-arsenic pigments under challenging environmental conditions.

Li, Z., Wang, L., Chen, H., & Ma, Q. (2020). Degradation of emerald green: scientific studies on multi-polychrome Vairocana Statue in Dazu Rock Carvings, Chongqing, China. Heritage Science, 8(1). https://doi.org/10.1186/s40494-020-00410-2