Covers the period from early Bronze Age to the 19th century and includes slags from an experimental smelting program. Analyses indicate little change in composition over the period; most primary tin slags contain from 10% to 30% stannous oxide in the glass phase, with tin metal prills more common in early and medieval slags. The principal impurities in the metal are iron and antimony, with smaller amounts of tungsten and arsenic. The Devon slags contain more titanium than the Cornish ones.