Revealing ancient yellow colorants in painted artworks along the silk Road (6th-10th century AD)

A comprehensive analytical protocol was undertaken to elucidate the yellow colorants employed in wall paintings from the Kizil Grottoes, the Taojia Tomb, the Baiyangzhai Tomb, and polychrome figurines from the Astana Tombs, all positioned along the historical Silk Road and dating to the 6th-10th centuries AD. To unequivocally identify these colorants, multi-analytical techniques were deployed, encompassing digital microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence spectroscopy (XRF), micro-Raman spectroscopy, and ultra-performance liquid chromatography triple quadrupole time-of-flight mass spectrometry (UPLC-Triple TOF-MS/MS). This comprehensive approach facilitated the unambiguous identification of both inorganic pigments, specifically vanadinite, and plant-derived colorants, including gamboge (Garcinia sp.) and Chinese cork tree (Phellodendron chinense), within these archaeological artifacts. These findings not only significantly enhance our scientific understanding of the materials and techniques utilized in the creation of these wall paintings and polychrome figurines, but also shed light on the vibrant exchange of materials and technological advancements that flourished along the ancient Silk Road.