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There is no geophysical method dedicated to the location, identification and analysis of early metalworking sites. There has only been limited application of these techniques to the study of such sites.

Unlike all the other metals used in the past, iron was produced and worked only in the solid state. This technology is called the ‘Direct Process’ of iron manufacture, ie the production of malleable iron direct from the ore. By contrast, in the later ‘Indirect Process’, the blast furnace produced liquid pig iron which had to be refined into malleable iron. This datasheet only deals with the direct process.

The direct or bloomery process comprised several stages. Metal was extracted from ore by smelting; raw iron was refined by primary smithing and was then manufactured into artefacts by (secondary) smithing. All these processes generated slags and residues as by-products.

The purity of gold could be estimated by using a touchstone but the only effective way of determining the purity of silver was by assaying (see below). Whatever their purity, much gold and silver had to be refined before use or re-use as they were often significantly debased. The process known as cupellation was used to separate precious metals from base ones, while silver was separated from gold by parting.

Crucibles and moulds are fairly easy to recognise and their identification should alert the fieldworker to the presence of metalworking on site. This provides an early opportunity to link the finds to associated materials (like scrap and waste metal, furnace lining and slags) and structural features, such as hearths.

Some of the vessels that may be identified as crucibles in the course of excavations were actually used for processes other than metal melting. Glass working is one of these processes (the vitreous deposits are relatively homogeneous and are mainly inside the crucible). Precious metals were refined using vessels that can be confused with crucibles; these processes and the finds associated with them are described in Datasheet 2.

Fuels for metallurgical and other industrial uses were derived from wood or from coal. The wood-based fuels comprised charcoal, white coal (kiln-dried wood) and fire-wood. Mineral coal was used either as mined or as coke. Over the post-medieval period there was a shift to coal, either due to the cost of suitable wood, or to inherent attractions of innovative coal-using processes.

This datasheet summarises the history of foundries, their buildings and residues.

This datasheet summarises blacksmithing proceses, buildings and residues.

Although an important aspect of medieval and earlier societies, the manufacture of steel was industrialised during the post-medieval period. Many complementary techniques were developed which often operated at the same time on the same site; there were also close links with other ironworking processes. This datasheet describes pre-20th century steelmaking processes in the UK, their material remains and metallurgical potential.

The manufacture iron from its ores can be carried out using a variety of smelting technologies. These can be broadly divided into the direct and indirect processes. The indirect process uses a blast furnace to create cast iron which is then refined into malleable iron. The direct or bloomery process produces malleable iron in a single furnace. The bloomery process took place below the melting point of the iron and bloomery iron had to be refined by forging before it could be used. All these processes generated slags and residues as by-products. The exact configuration of raw materials, furnace architecture, and other factors means that there are many variations within bloomery smelting and this may be reflected in the nature of the slags and residues.