GC/MS investigations of the total lipid fraction of wool: A new approach for modelling the ageing processes induced by iron-gallic dyestuffs on historical and archaeological textiles

Abstract

In order to understand the pathways leading to the degradation of wool in historical and archaeological textiles dyed with iron tannin dyestuffs, a new approach entailing the determination of the wool lipid component by gas chromatography/mass spectrometry (GC/MS) was used. A wide number of reference specimens prepared with five different plant tannin, also subjected to accelerated ageing, were analysed and the results were interpreted by principal component statistical analysis (PCA). Results indicate that 4-hydroxybenzoic acid and dicarboxylic acids can be considered as markers of ageing, and that the use of both an iron mordant and a tannin dyestuff caused a detrimental effect on the fibres, similar to that achieved by artificial ageing. In particular, we observed the occurrence of oxidation immediately after the mordanting step. The suitability of the described molecular markers for evaluating the degradation of textiles was validated by analyzing several samples collected from historical and archaeological fabrics of different periods and geographical origin. The profiles of the historical and archaeological samples matched those of the artificially aged samples, thus confirming the reliability of the applied method to evaluate the degradation of the different threads in a fabric.