The survival of metal objects in the archaeological record is somewhat variable (possibly because metals are relatively easy to recycle) but almost every archaeological excavation in the UK yields at least some slag—the waste product of working metals. The visual examination and cataloguing of slags (as well as crucibles, moulds and other archaeometallurgical debris) can provide the evidence to identify the exact nature of the metal being worked as well as the process. The size, shape, texture, colour and density of a specimen of slag are all clues to the processes that formed it.
Archaeometallurgical evidence can include whole landscapes (waste heaps), buildings, structures (standing furnaces), features, artefacts and waste materials (eg slag and crucibles). Archaeometallurgy includes fieldwork investigations (survey and excavation) and the subsequent study of these data as well as any artefacts and residues recovered. Scientific approaches provide insights into the techniques used to produce different metals and how these were fabricated into artefacts (occasionally supplmented with experiments to reconstruct past archaeometallurgy).
The scientific examination of waste materials, which can include the chemical analysis of the metal (and any inclusions) and the imaging of the internal microstructure, can confirm the exact nature of the metal being worked and provide insights into every stage of manufacture from selection of ore to the nature of the production process.