Investigating the provenance of Egyptian blue pigments in ancient Roman polychromy

Abstract

Egyptian blue is a copper-based blue pigment that was widely used across the Mediterranean from ca. 3300 BC up to late antiquity and even later. For this case study, we analyzed the provenance of Egyptian blue from a Campana relief from the collection of the Ny Carlsberg Glyptotek, Denmark. Campana reliefs are terracotta plaques, which were named after the Italian collector Gampietro Campana, who published the first collection in 1851. These mould-made plaques were used as ornaments in central Italy from ca. 60 BC to 50 AD – a time when Egyptian blue production is attested at several sites in the Bay of Naples, Italy. The provenance of copper raw materials that were used for producing this pigment could provide clues about the distribution of production centers and trade contacts. A previous investigation of the provenance of a single bulk Egyptian blue sample of this artefact by Rodler et al. (2017) indicated a possible long-distance transport of (Iberian) copper ore or mixing of distant (Iberian) and Italian copper. Our new data are based on the lead isotope analysis of four individual Egyptian blue samples. The refined sampling resolution emphasizes the Italian South-Eastern Alps as the most likely source area of copper raw materials. This copper could have been processed in local Egyptian blue production workshops or brought to the contemporary Egyptian blue production hub in the Bay of Naples and transported from there to the workshop where the artefact was painted.