Keys to the Past

Glossary

Slag; Slag heaps

The unwanted remains from heating event carried out in a furnace. This may contain remains of the ore, fuel, and materials intended to be created, and so be specific to a purpose - e.g. ironstone smelting or glass production, and to a specific method of production, such as bloomery or blast furnace production of iron.

The specific nature of the activity carried out can be based on the shape of (see tap slag), quantity of, chemical analysis of and distribution of the slag. Sometimes slag will be the most visible sign of that process on the surface - large slag heaps sometimes have a different vegetation cover to that of the surrounding area, but the amount present can vary widely. Sometimes Medieval slag was robbed to be smelted down by improved Post-Medieval technologies, such as blast furnaces, or for road-metalling and as an addition to fields.

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