The analysis of dyestuffs from first- to second-century textile artefacts found in the Martres-de-Veyre (France) excavations

A series of Gallo-Roman clothes and miscellaneous textile fragments from the first and second centuries from the Martres-de-Veyre necropolis (Puy-de-Dome, France) was investigated. The objects studied were excavated between 1851 and 1923, during successive rounds of archaeological work. Since that time, they have been conserved in the Barguin Museum at Clermont-Ferrand. The target of our research was dye identification, as it gives very interesting and useful information regarding the ancient technology. This approach has until now not been considered to be relevant and, unfortunately, is not systematic. The analysis was carried out by high-performance liquid chromatography with photodiode array detection (HPLC-PDA). The small samples (threads up to 0.6 mg, less than 1 cm long) of coloured textile fibres were submitted to this technique. In one case, X-ray fluorescence (XRF) analysis was applied. According to the analysis, the dyeing sources proposed are the Rubiaceae family for red, a luteolin 'base' for yellow, ellagitannins for brown and indigo for blue colours. Several samples did not seem to contain any dye. We point out possible factors for the partial dye source determination: instrumental limits, sample size, low dyestuff content in analysed samples and the dyes' decomposition during ageing. Some improvements of dye analysis in archaeological samples by separation techniques based on recent analytical instrumentation and combined approaches are proposed.