Scientific Characterization of Mural Materials from a Tubo-Period Tomb in Qinghai, China

The murals from Tomb No. 1 at Wulanquangou, Qinghai, China (633–842 CE), provide insights into mural materials and painting techniques during the Tibetan Empire. In this study, OM, SEM–EDS, XRD, μ-RS, FTIR, Py–GC/MS, ELISA, and LPSA were employed to characterize the mural materials and painting techniques. The murals comprise a multilayer structure consisting of brick and squared timber (Cupressus spp.) supports, an earthen ground layer, a lime ground layer, and a pigment layer. The lime ground is dominated by calcite, whereas the earthen ground consists mainly of fine-grained silty soil reinforced with highland barley fibers. Hematite, carbon black, and indigo were identified in the pigment layer, while animal glue was identified as the binding medium. The identification of indigo provides the first evidence of its use in a Tubo-period mural on the Qinghai–Tibet Plateau. Similarities in mural structure and painting techniques between Wulanquangou Tomb No. 1 and high-status Tang tomb murals in Shaanxi and Gansu suggest possible technological exchanges between the Tibetan Empire and Tang China.