Removal of natural organic dyes from wool- implications for ancient textile provenance

TY - JOUR

T1 - Removal of natural organic dyes from wool- implications for ancient textile provenance

AU - Frei, Karin Margarita

AU - Vanden Berghe, Ina

AU - Frei, Robert

AU - Mannering, Ulla

AU - Lyngstrøm, Henriette Syrach

PY - 2010/9

Y1 - 2010/9

N2 - 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.

AB - 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.

KW - Faculty of Humanities

KW - Ancient textiles

M3 - Journal article

SN - 0305-4403

VL - 37

SP - 2135

EP - 2145

JO - Journal of Archaeological Science

JF - Journal of Archaeological Science

ER -