Polychromic structures and pigments in Guangyuan Thousand-Buddha Grotto of the Tang Dynasty (China)

► A multi-analytical study of the polychromy in ancient Chinese Grotto is presented. ► The polychromic structures are recognized as the monolayer or multilayer in 15 samples. ► The main pigments are identified as green, red, blue and white materials. ► Arsenic-containing pigment is detected in the green samples. ► The most completed color-stratigraphy is characterized as five color sections.