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Karin Margarita Frei, Ina Vanden Berghe, Robert Frei, Ulla Mannering, Henriette Lyngstrom, "Removal of natural organic dyes from wool-implications for ancient textile provenance studies," Journal of Archaeological Science, Volume 37, Issue 9, September 2010, Pages 2136-2145, ISSN 0305-4403, DOI: 10.1016/j.jas.2010.02.012.
(http://www.sciencedirect.com/science/article/B6WH8-4YH4R61-3/2/4a75969b69c21e553abce4e4cf47e593)
Keywords: Ancient textiles; Organic dyestuff; Strontium isotopes; Wool; Provenance
Abstract
Ancient wool textiles recovered from archaeological sites are in many cases originally dyed with natural organic dyestuffs from vegetable sources. These include among others woad (Isatis tinctoria L.), weld (Reseda luteola L.), and madder (Rubia tinctorum L.). These dyestuffs could be a threat to the use of the strontium isotopic system as a tracer for provenance studies of ancient wool, because they could potentially contaminate the signature of the textile's raw material. We present a novel method which allows for efficient removal of organic dyestuffs in wool prior to strontium isotopic analysis. Our method is based on an oxidative release of the dyestuff constituents by ammonium peroxodisulfate [(NH4)2S2O8] solution, combined with hydrofluoric acid (HF) that has shown to effectively remove/dissolve adhering dust micro-particles. Our multi-analytical results show that such a pretreatment is capable of removing >98% of the originally present organic dyestuffs without significantly destroying the wool structure. The strontium isotopic ratios of the residual wool fraction after the application of the pretreatment are sensitive to the origin and, therefore, can be used as tracers for the provenance of the raw material. We propose to apply this method to ancient wool textiles in which positive identification of organic dyestuff constituents by High Performance Liquid Chromatography (HPLC) was made.
(http://www.sciencedirect.com/science/article/B6WH8-4YH4R61-3/2/4a75969b69c21e553abce4e4cf47e593)
Keywords: Ancient textiles; Organic dyestuff; Strontium isotopes; Wool; Provenance
Abstract
Ancient wool textiles recovered from archaeological sites are in many cases originally dyed with natural organic dyestuffs from vegetable sources. These include among others woad (Isatis tinctoria L.), weld (Reseda luteola L.), and madder (Rubia tinctorum L.). These dyestuffs could be a threat to the use of the strontium isotopic system as a tracer for provenance studies of ancient wool, because they could potentially contaminate the signature of the textile's raw material. We present a novel method which allows for efficient removal of organic dyestuffs in wool prior to strontium isotopic analysis. Our method is based on an oxidative release of the dyestuff constituents by ammonium peroxodisulfate [(NH4)2S2O8] solution, combined with hydrofluoric acid (HF) that has shown to effectively remove/dissolve adhering dust micro-particles. Our multi-analytical results show that such a pretreatment is capable of removing >98% of the originally present organic dyestuffs without significantly destroying the wool structure. The strontium isotopic ratios of the residual wool fraction after the application of the pretreatment are sensitive to the origin and, therefore, can be used as tracers for the provenance of the raw material. We propose to apply this method to ancient wool textiles in which positive identification of organic dyestuff constituents by High Performance Liquid Chromatography (HPLC) was made.
