Identification of purple dye from molluscs on an excavated textile by non-destructive analytical techniques

The inherent sensitivity of textile fibres to the aggressive process of burial accounts for the rarity and poor condition of excavated textile finds retrieved. However, the information contained within these finds is important and yielding it contributes to the longevity of the finds. Therefore, the application of non-destructive methods of investigation for the extraction of the data present is imperative. This paper presents the results of dye analysis performed on the excavated textile find HTR-73 from the Kerameikos cemetery in Athens. The Kerameikos textile find is from the 5th century BC, and has been preserved in association with copper. The techniques applied were Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, Cathodoluminescence and micro Raman. For the first time Cathodoluminescence from an indigoid compound is reported. Comparison of the analysis results on samples from the find with the contemporary reference samples lead to the identification of purple dye as a dibromoindigo compound with the origin from molluscs of Murex trunculus species. The application of non-destructive analytical methods of investigation was successful in analysing dyes on excavated textiles.