The identification of lac as a pigment in ancient Greek polychromy - The case of a Hellenistic oinochoe from Canosa di Puglia

Abstract

An important example of a mixture of red colourants from plant and insect sources has been found during a recent investigation of a purple pigment on a 3rd century BC oinochoe from Canosa di Puglia present in the British Museum collection. Further investigation was carried out to elucidate both the nature of this pigment and its possible method of manufacture. In a practice typical of the period, Egyptian blue and a pink lake were found to be physically mixed to produce the purple pigment observed on the object. High pressure liquid chromatography coupled with mass spectrometry (HPLC-MS) revealed that the main colourant of the pink lake was derived from madder (Rubia spp.). However, the samples investigated also contained markers for insect-derived colourants from cochineal (Porphyrophora spp., in partial agreement with recent archaeological findings from Thessaloniki) and lac (Kerria Lacca Kerr). Despite allusions to its existence in ancient sources, evidence for the use of lac dye as a colourant (in a lake pigment) from Antiquity has never previously been found. In addition, markers indicative of tannins were also found in the mixture. This was interpreted as an indication of the reuse of a colourant that has been extracted from previously dyed textiles. Although common practice in the manufacture of red lakes from the 14th to 17th centuries, this may be the first evidence for this method to produce lake pigments found on an object from Antiquity.In addition to confirming the power of HPLC-MS in terms of the sensitivity and specificity of information, that in many cases allows species differentiation, these discoveries raise many questions, not least of which is the real extent of use of insect-derived colourants, as part of the polychrome palette of these votive objects and ancient polychromy in general. The implications of this use in the wider context of pigment manufacture in Antiquity, particularly in terms of the trade in raw materials, must also be considered.