Multi-analytical investigation on materials and techniques of wall paintings in Kizil Giant Buddha Cave

This study investigates the wall paintings in Cave No. 47 of the Kizil Grottoes, the earliest surviving Giant Buddha cave. p-XRF, SEM-EDX, XRD, and micro-Raman spectroscopy were used to characterize the painting materials, stratigraphy, and alteration products. Three plaster and painting techniques were identified: direct painting on rock, painting on a single plaster layer, and multilayered painting. The plaster preparation strategy varied according to spatial location and pigment type. Alteration of lead-based pigments accounts for most black and light-yellow areas. Tenorite, reported here for the first time in Kizil wall paintings, probably formed through fire-related alteration of basic copper chloride pigments. Paratacamite, high-purity lazurite, arsenic-bearing green pigments, and fire-related anhydrite were also identified. These findings clarify material choices and degradation mechanisms in Kizil Giant Buddha Cave No. 47 and provide evidence for conservation.