Chemical evidence for the spread of lac colorant in Xinjiang from the 2^nd to 9^th centuries CE

Lac dye, indigenous to South and Southeast Asia, is historically accepted to have entered Xinjiang during the Han Dynasty through trade routes established between India and China, and later from the 5^th century CE, when Buddhist art started flourishing in the region. The dynamics of trade and colorant applications of lac in the region has been constrained by the limited availability of historical written sources, archeological materials, and scientific investigations. Using ultra-performance liquid chromatography with photo diode array detection and mass spectrometry (UPLC-PDA-MS), this study explores the characterization of lac in a small group of archeological textiles, wall paintings, and painted sculptures, dated between the 2^nd and 9^th century CE. It aims to undertake a first attempt to historically trace the dissemination of the insect dye between India and Northwest China, and within the broader framework of trade and cultural exchange along the Silk Roads in the first millennium CE.