Resurrecting a Graeco-Egyptian Purple: Reverse Engineering an Ancient Pigment of Scientific and Cultural Significance

摘要

In ancient Graeco­Roman Egypt, funerary portraits painted in the encaustic style often indicated the deceased individual’s socioeconomic status through depicted adornments and clothing. For example, purple clavi ­ such as the clavus in “32.6 The Bearded Man” ­ used their color to distinguish higher social castes from the common population. Traditionally, high­quality purple dye was painstakingly extracted from the Murex sea snail; however, this expensive colorant’s use primarily as a dye rather than a pigment motivated the development of less costly organic dyes for lake pigment production. We explored the processing of several dye precursors accessible to Graeco­Egyptians of antiquity (kermes, lichen, indigo, madder and alkanet roots ­ which can all be color­shifted to purple by a variety of metal and alkali salts) in order to characterize the production of the purple used in “The Bearded Man.” Spectroscopic techniques such as raman, absorption, fluorescence, and XRD offer comparative chemical, physical, and optical analyses of the dyes and pigments that result from the various precursors and the addition of metal and alkali salts. Pigments produced experimentally are compared with a sample from “The Bearded Man” in order to better correlate the processing materials and methods available in ancient Graeco­Roman Egypt.