Intentional patina of metal archaeological artefacts: non-destructive investigation of Egyptian and Roman museum treasures

Abstract

This paper describes microstructural analyses by X-ray portable diffraction and microdiffraction on intentional patina of the bronze museum objects from antique Egypt and the Roman Empire. They bring evidence of the presence in the true black bronze patinas of metallic gold and/or silver presumably as nanoparticles. Three other Egyptian patinas not belonging to black bronze are characterised. Apparent black patination on a Roman scalpel handle is discussed. The discovery of a new patination procedure on Roman artefacts from the Louvre museum is also related, based on intentional high temperature oxidation to obtain a dark patina on a lead bronze object. A presence of lead carbonate cerussite is an important observation.