Dye Components in Insect Lac (Shellac) of the American Southwest

Date and Time: 
Friday, 12 May, 2017 - 09:30
, Christina - Detroit Institute of Arts
, Chika - Arthur M. Sackler and Freer Gallery of Art, Smithsonian Institution
, Marilen - Arizona State Museum, University of Arizona
, Nancy - Arizona State Museum, University of Arizona

The exudate from lac insects (Tachardiella spp.) is used as an adhesive throughout the cultures of Southwest.  It was used extensively by the O’odham and Seri, and in the archaeological record it has been found in Hohokam, Mogollon and Ancestral Puebloan artifacts.  This insect exudate also contains a red dye:  in Asian lac (Kerria spp.), this dye (“lac dye”) is extracted and used commercially.  The dye from Tachardiella spp. was analyzed with liquid chromatography mass spectroscopy and was found to contain the same dye components as Asian lac dye but in a different proportion. Using this unique distribution of dye components, it is possible to distinguish American from Asian shellac.  This technique was used to analyze a sample from a repair on a Tohono O’odham vessel (1700-Present) in the collections of the Detroit Institute of Arts, and results show it is consistent with an indigenous repair.