Archaeology Datasheet 06
Bloom refining and smithing slags and other residues
The smelting of iron by the direct process results in a bloom, which must be refined to produce forgeable iron stock. Blooms produced from bog ores in a non-tapping furnace would have had more entrapped slag and would have needed more refining than the cleaner blooms made from an ore which could be smelted by slag tapping. At least the initial stages of refining would be carried out at the smelting or primary production site, so that both smelting and refining residues can be found together.
Once refined the iron stock would be traded to the blacksmithing community and the smithing or forging of the iron would be carried out at a secondary production site, which could be a specialised workshop or a small forge attached to a settlement or a farm.
All the stages of refining and smithing produce broadly the same kinds of structural and residue evidence and there is little of it which is diagnostic of a specific stage of the process. The characterisation and interpretation of this kind of evidence depends mainly on the size and relative quantities of the different types of residue.