Pigments, Dyes and the Restoration History of the Painted Figurines of the Tang Dynasty from the Astana Tombs Revealed by Comprehensive Chemical Analysis

Comprehensive micro-analyses were conducted to identify different pigments and dyes used in painted figurines of the Tang Dynasty unearthed from Astana Tombs, located along the ancient Silk Road. Interestingly, a mixture of lazurite and indigo was first discovered on a painted figurine to create a special blue hue, demonstrating that ancient Gaochang craftsmen were already skilled in using mixed colorants. Moreover, superimposition techniques were as well applied in these painted figurines, such as hematite or cinnabar overlaid on red lead. Despite the lack of unambiguous restoration records in the last century, multiple synthetic organic colorants used for repainting the lokapala figurine were successfully identified by Raman spectroscopy and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), which should be helpful for the retrospective documentation of the restoration history of these artworks. These investigations towards archaeological materials can provide precise historical facts about the artworks and fundamental knowledge for their conservation.