Puddled Iron

Puddling is a technique, perfected by Henry Cort in 1784, for making pure iron from pig iron.

By the mid-1700's, there arose a need for higher quality iron. The method used to refine charcoal iron was called "Puddling." Bars of charcoal iron were heated in a furnace by an indirect coal fire. Molten iron was then cast into ingots (pigs) and stacked one way the other in a pile on the Puddling hearth. Here it was heated and "puddled" to remove impurities (the "puddlers" stirred the liquid). Impurities burned off and the puddled iron formed pasty balls.
Puddled iron was then transferred to the shingling hammer (a gigantic power hammer which was capable of earth-shattering blows) which formed the iron into a billet. This was then rolled, cut up into lengths, re-stacked and the whole process repeated over again. The more times the process was repeated, the better was the quality of the finished wrought iron.

Puddling superseded wrought iron working by hand and the introduction of the technique made a significant contribution to the industrial revolution.