text: Puddled iron—the puddling process was the first large-scale process to produce wrought iron. In the puddling process, pig iron is refined in a reverberatory furnace to prevent contamination of the iron from the sulfur in the coal or coke. The molten pig iron is manually stirred, exposing the iron to atmospheric oxygen, which decarburizes the iron. As the iron is stirred, globs of wrought iron are collected into balls by the stirring rod (rabble arm or rod) and those are periodically removed by the puddler. Puddling was patented in 1784 and became widely used after 1800. By 1876, annual production of puddled iron in the UK alone was over 4 million tons. Around that time, the open hearth furnace was able to produce steel of suitable quality for structural purposes, and wrought iron production went into decline.
  Oregrounds iron—a particularly pure grade of bar iron made ultimately from iron ore from the Dannemora mine in Sweden. Its most important use was as the raw material for the cementation process of steelmaking.
  Danks iron—originally iron imported to Great Britain from Gdańsk, but in the 18th century more probably the kind of iron (from eastern Sweden) that once came from Gdańsk.
  Forest iron—iron from the English Forest of Dean, where haematite ore enabled tough iron to be produced.