Portable XRF on prehistoric bronze artefacts: Limitations and use for the detection of bronze age metal workshops

Abstract

Two different scientific analyses-one destructive and one non-destructive-were conducted on two separate groups of bronze ornaments dating from 1500-1100 BC to investigate, amongst other traits, the metal composition of their copper-tin alloys. One group of artefacts was sampled, and polished thin sections were analysed using a scanning electron microscope (SEM). Results from the corrosion crust of copper-tin alloys, and the change measured within the elemental composition from the bulk metal to the surface, greatly influenced the interpretation of the second data set, which was measured using a handheld X-ray fluorescence (XRF) device. The surface of corroded bronze ornaments consists mostly of copper carbonates, oxides, and chlorides. Chemical processes, such as decuprification, change the element composition in such a manner that the original alloy cannot be traced with a non-destructive method. This paper compares the results of both investigations in order to define the possibilities and limits of non-destructive XRF analyses of corroded bronze artefacts.