A multi-analytical approach for the characterization of red dyestuffs used in ancient tapestries : construction of a reference database

The study here presented concerns the characterization, with chromatographic (high-performance liquid chromatography, HPLC) and spectroscopic (Raman spectroscopy and UV-Vis spectroscopy) techniques, of red dyestuffs used to dye the yarns of ancient tapestries. Following the ancient recipes the yarns (wool and silk) have been dyed using natural red dyes such as madder, kermes and cochineal. By SEM-EDX (scanning electron microscopy coupled with energy dispersive X-ray analysis) the yarns morphology has been investigated and the presence of the metals responsible for the specific mordants employed has been highlighted. The samples thus obtained have been studied in order to build a reference database that can be used later for the identification of the dyes used by the ancient tapestry manufacturers. Attention has been also paid to develop a non-destructive approach to be applied in-situ.