The technical revolution in production
The production of iron increased rapidly during the 18th century.
By the time Nash set to work in 1815 the production of basic pig iron in Britain was 400,000 tons (406,420 tonnes) per annum, as against about 23,000 tons (23,369 tonnes) a century earlier. The tremendous expansion in output of iron forms a central theme in every account of the industrial revolution, its significance unchallenged though the reasons for it are still the subject of debate. All are agreed that the starting point was the discovery by Abraham Darby I in 1709 of a method of smelting iron with coke. If it had still been reliant on charcoal the industry could not have met the increased demand of the second half of the century. Coke-smelting provided increased capacity, especially once steam power was used for blowing, and it enabled cast iron to be produced more easily.
Further developments in iron production methods took place gradually.
After the 18th century innovations had taken hold, the smelting process underwent no further change until the 1830s, when the introduction of the hot blast process permitted uncoked coal to be used in furnaces and increased their efficiency yet more. Improved iron smelting was complemented from the 1780s by the transformation of the forging process in which pig iron was converted to workable wrought iron.
The ironmaster Henry Cort took out two patents in 1783-4, one for a coal-fired reverberatory furnace and the other for a method of powered rolling the bloom of iron (as it was known) into standard shapes, initially, square and round bars. Without the ability to roll wrought iron the structural advances which it eventually permitted would never have taken place.
