AIC's 47th Annual Meeting

The source of the blue colorant found in Chilkat blankets woven by the Tlingit peoples in NW Alaska has been a source of confusion for decades. In 1907, U.S Navy Lt. G.T. Emmons (and anthropologist Franz Boas) wrote papers on the Chilkat blanket (in Memoirs of the American Museum of Natural History) suggesting that blue-green coloration was the product of fetid urine in copper vessels which was later supplanted by aniline dyes. The paper was reported by W.D. Darby in 1917 to American industrial dyers (Color Trade Journal), to Canadians by D. Leechman (Transactions, Royal Society of Canada, 1932), and summarized again by Leechman (Brooklyn Botanic Garden’s Dye plants and Dyeing: a Handbook, 1964). In 1982, Cheryl Samuel thoughtfully tried to update and accommodate this reportage with research of the Canadian Conservation Institute and the University of British Columbia, who found the blue to be indigo, free of copper, they also reported that urine treated copper was fugitive to wool. Yet, in 1988, colleagues at the Canadian Museum of History found all the dyes in an early 19th century Chilkat tunic were fugitive to water. When four National Museum of Natural History Chilkat textiles were analyzed by portable XRF for mordants in 2006, the blue dyes, like the yellow colorants, lacked a mordant level of copper. We have recently analyzed blue fibers from three NMAI Chilkat blankets using direct analysis in real time mass spectrometry (DART-MS) and found urea, isatin, indoxyl, and indigo. A re-reading of Emmons in reprint form included appendices of corrections for language, plant, and bird identifications. Amendments also seem relevant for the dyeing procedures he describes. Dye literature by dyers, routinely describe about the coppery green appearance of the leuco (aka reduced, white) form of the indigo vat. Modern literature on lant and reduction reinforce the distinctive processes associated with the various forms of reduction fermentation. These were quickly superseded in the early 1900’s by a newly available commercial sodium dithionite. By revisiting older literature, records, and dyeing procedures with a clearer understanding, and the actual objects with new technologies, some of the confusions about the colorants in Chilkat blankets now may be resolved.