Lancashire hearth

The Lancashire hearth was used to fine pig iron, removing carbon to produce wrought iron.

Until the early 19th century, the usual method of producing wrought iron involved a charcoal-fired finery in a finery forge. In the beginning of the 19th century this became an obsolete process and was slowly replaced by the coal-fueled puddling process. However, charcoal continued to be used in some forges after most of the iron industry had abandoned it for coke.

In 1813 when John Bradley & Co. (whose leading partner was James Foster) took over forges at Eardington in Shropshire, a potting and stamping forge, they reverted to using charcoal. In 1820, he bought Hampton Loade Forge, which then became a tinplate works and in 1826 another charcoal forge. This was followed by other charcoal forges at Horsehay in 1832 and at the Old Park ironworks of the Botfield family about 1826. Cookley Forge in the Stour valley also reverted to charcoal working in 1814, supplying wire and tinplate mills.

By the 1830s, these forges were sometimes producing over 2000 tons of iron per year, compared with a few hundred from earlier finery forges. It is likely that these forges were using a more efficient variety of hearth, which from Swedish usage has come to be known as a Lancashire hearth.

Faced with competition from cheaper British iron production, the Swedish iron industry needed to find a new cheaper method of making iron. In the 1810s, experiments were made with puddling, but this proved unsatisfactory, as it needed coal of which Sweden had none. After Gustav Ekman visited Britain, he published a report of his observations. He had seen closed finery hearths in south Wales and near Ulverston, then in Lancashire (now Cumbria). Those in south Wales were similar to puddling furnaces, but in Lancashire, he saw closed furnaces, where the metal was in contact with the fuel. On his return to Sweden, Ekman experimented and built furnaces similar to what he had seen near Ulverston, most probably at Newland ironworks.

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