The two major classes of nonmetallic evidence for metalworking are crucibles and molds. Crucibles show continuous change in both form and fabric from Iron Age to late medieval times and a number of them had uses other than metal melting; brassmaking (cementation) crucibles and cupels have been identified. Molds were used to cast both blanks or ingots and objects. Investment molds were used from the Iron Age onwards but the bulk of Roman and later molds were piece molds. All the finds discussed come from recent excavations in Britain.