paul+mills

SUBJECT AREA: Metallurgy

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Darby's father, John, was a farmer who also worked a small forge to produce nails and other ironware needed on the farm. He was brought up in the Society of Friends, or Quakers, and this community remained important throughout his personal and working life. Darby was apprenticed to Jonathan Freeth, a malt-mill maker in Birmingham, and on completion of his apprenticeship in 1699 he took up the trade himself in Bristol. Probably in 1704, he visited Holland to study the casting of brass pots and returned to Bristol with some Dutch workers, setting up a brassworks at Baptist Mills in partnership with others. He tried substituting cast iron for brass in his castings, without success at first, but in 1707 he was granted a patent, "A new way of casting iron pots and other pot-bellied ware in sand without loam or clay". However, his business associates were unwilling to risk further funds in the experiments, so he withdrew his share of the capital and moved to Coalbrookdale in Shropshire. There, iron ore, coal, water-power and transport lay close at hand. He took a lease on an old furnace and began experimenting. The shortage and expense of charcoal, and his knowledge of the use of coke in malting, may well have led him to try using coke to smelt iron ore. The furnace was brought into blast in 1709 and records show that in the same year it was regularly producing iron, using coke instead of charcoal. The process seems to have been operating successfully by 1711 in the production of cast-iron pots and kettles, with some pig-iron destined for Bristol. Darby prospered at Coalbrookdale, employing coke smelting with consistent success, and he sought to extend his activities in the neighbourhood and in other parts of the country. However, ill health prevented him from pursuing these ventures with his previous energy. Coke smelting spread slowly in England and the continent of Europe, but without Darby's technological breakthrough the ever-increasing demand for iron for structures and machines during the Industrial Revolution simply could not have been met; it was thus an essential component of the technological progress that was to come.

Darby's eldest son, Abraham II (1711–63), entered the Coalbrookdale Company partnership in 1734 and largely assumed control of the technical side of managing the furnaces and foundry. He made a number of improvements, notably the installation of a steam engine in 1742 to pump water to an upper level in order to achieve a steady source of water-power to operate the bellows supplying the blast furnaces. When he built the Ketley and Horsehay furnaces in 1755 and 1756, these too were provided with steam engines. Abraham II's son, Abraham III (1750–89), in turn, took over the management of the Coalbrookdale works in 1768 and devoted himself to improving and extending the business. His most notable achievement was the design and construction of the famous Iron Bridge over the river Severn, the world's first iron bridge. The bridge members were cast at Coalbrookdale and the structure was erected during 1779, with a span of 100 ft (30 m) and height above the river of 40 ft (12 m). The bridge still stands, and remains a tribute to the skill and judgement of Darby and his workers.

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