Pigments and binding media of polychrome relics from the central hall of Longju temple in Sichuan, China

Longju temple, located in Guanghan County, Sichuan province of China, is a Buddhist temple with great cultural significance. It has preserved polychrome relics since 1466 of the Ming dynasty. The deterioration of these ancient colored paintings is posing an extremely serious issue, it is exceptionally critical to propose an appropriate protection plan. In this paper, pigments and binding media were analyzed from ten polychrome samples collected from the central hall of Longju temple. A series of analysis methods were adopted, including the Raman spectrum, scanning electron microscopy-energy disperse spectrometer (EDS-SEM), and enzyme-linked immunosorbent assay (ELISA). Results demonstrate the existence of atacamite, azurite, carbon black, cinnabar, and gold in the color layer of the samples. Egg white, animal glue, and casein were found to be used as binders in the colored paintings. This study not only offered essential data for the follow-up protection and repair projects but also provided a reference to further explore the polychrome relics of other Buddhist temples in the Ming dynasty of China.