text: In Swedish Uppland north of Stockholm and certain adjacent provinces, another kind known as the Walloon forge was used, mainly for the production of a particularly pure kind of iron known as oregrounds iron, which was exported to England to make blister steel.  Its purity depended on the use of ore from the Dannemora mine.  The Walloon forge was virtually the only kind used in Great Britain.
  The forge had two kinds of hearths, the finery to finish the product and the chafery to reheat the bloom that was the raw material of the process.