At Coalbrookdale Museum, we learnt that ;
The blast furnace revolutionised the iron-making process. The first blast furnace in Britain was built in 1491 at Buxted in the Weald. These furnaces had already been in use on the Continent for some years, and the technology is thought to have been imported to the south of England by French or Belgium iron- makers. The introduction of the blast furnace marked a major turning point in the development of iron-working. Blast furnaces accelerated production, gave greater quantities of iron, and iron could be directly cast from the furnace into moulds.
Early blast furnaces were fuelled with charcoal. Water was used to power bellows, which delivered a constant blast of air into the furnace. Iron ore and limestone were put into the top of the blast furnace. By heating up these raw materials the iron was separated from the iron ore. This liquid pig iron was drained or tapped from the base of the furnace.
This iron was run into moulds to make items like fireback’s, cannons and cannon shot. Alternatively, it could be cast in sand moulds shaped as ingots (known as ‘pigs’), which in turn could then be turned into wrought-iron in a forge. Pig iron could either be re-melted to make cast-iron items or worked to further refine it and turn it into wrought –iron.
Pig iron has a carbon content of 4-5% and could be forged like wrought –iron it was first re-melted in a finery to burn out the carbon, producing a mass of iron, which was then beaten under a hammer to consilidate it (‘shingling’). Then it was heated again in a chafey and further hammered into an iron bar ready for sale. 90% of all pig iron was converted to wrought iron in the seventeenth century.