Bloomery ironmaking during the Roman period in mid-Norway
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Abstract
Finds of bloomery sites in the counties of South and North Trøndelag in Norway have indicated large-scale ironmaking, starting in the pre-Roman Iron Age and lasting until the Merovingian period. The industry was based on rich deposits of bog iron ore. Museum blooms from the period weigh around 18kg and are free from slag as well as sulphur and phosphorus. The carbon content is normally very low, but one bloom shows that steel could have been produced. The normal slag has an optimal character when fluidity and refining capacity are evaluated. The use of induced draught created by direct addition of wood is suggested, based on finds and experiments. Slag control of the carbon content of the iron was probably achieved by a cyclic operation. As the output calculated for Trøndelag exceeds local needs, export of iron is suggested. Iron metallurgy sheds light on a period of Norwegian history not well covered by other sources.
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