Introduction: Analyses of natural dyes and the metal of the metal-wrapping threads used in 16^th -18^th century Persian/Safavid and Indian/Mughal period velvets were performed on these textiles in the collection of The Metropolitan Museum of Art. The purpose was to determine whether velvets from the two cultures, which have shown problems in the past with attribution based on historical and iconographical studies, could be more precisely differentiated with the additional evidence from identification of their natural dyes and metals along with information of weaving techniques. Dyes and metal of the metal-wrapped threads from fifteen Persian velvets and six Indian velvets were analyzed by high performance liquid chromatography with photo diode array detector and by scanning electron microscopy with energy dispersive X-ray spectrometry respectively. Results: There seem to be types of dyes which specifically characterize the velvets of each culture, as well as types of dyes commonly found in velvets of both cultures. Dyes typical of Persian velvets are cochineal and yellow larkspur, while lac and turmeric are characteristic of Indian velvets. The dyes commonly found are a combination of yellow larkspur and indigo dye in green, as well as safflower, indigo dye, soluble redwoods, and tannin dye. There were exceptions however. Because of those exceptions, examining the range of dyes used in the velvets would be important in differentiating the velvets. Metal used for wrapping the threads was in all cases found to be silver of fairly high purity, the majority of which had been gilded. The silver from Persia metal threads showed very slightly higher copper content, while Indian threads showed nearly pure silver. This is the first extensive comparative study of dyes and metal threads of Safavid and Mughal velvets: the first evidence of yellow larkspur being the most used yellow dye in Persia, and of the possible differences in the two cultures’ metal threads. Conclusion: In addition to knowledge gathered from investigation of weave structure and from historical and iconographic studies, analysis of dyes and metal threads will contribute to a clearer differentiation of those two cultural groups of textiles.

As part of a long-term campaign to document, study, and conserve the Heroes tapestries from The Cloisters collection at The Metropolitan Museum of Art, organic colorant analysis of Julius Caesar (accession number 47.101.3) was performed. Analysis with liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-qToF-MS) revealed the presence of several multiply chlorinated xanthones produced only by certain species of lichen. Various lichen dye sources have been documented in the literature for centuries and are classified as either ammonia fermentation method (AFM) or boiling water method (BWM) dyes based on their method of production. However, none of these known sources produce the distinctive metabolites present in the tapestry. LC-qToF-MS was also used to compare the chemical composition of the dyes in the tapestry with that of several species of crustose lichen. Lichen metabolites, including thiophanic acid and arthothelin, were definitively identified in the tapestry based on comparison with lichen xanthone standards and a reference of Lecanora sulphurata, confirming the presence of a lichen source. This finding marks the first time that lichen xanthones have been identified in a historic object and the first evidence that BWM lichen dyes may have been used prior to the eighteenth century.