Which process did Henry Cort patent in 1784 to refine pig iron?

Henry Cort patented an improved puddling process in 1784 to refine pig iron into wrought iron. In puddling, molten pig iron was stirred in a coal-fired reverberatory furnace, where exposure to air burned away much of its carbon and produced a pasty mass of wrought iron.

The resulting iron was gathered into a ball, then mechanically worked by shingling and rolling to make usable bar iron. Puddling was important because it reduced dependence on charcoal and helped Britain produce much larger quantities of iron during the Industrial Revolution.

Cort did not invent every element from scratch. Peter Onions had developed successful commercial puddling at Dowlais in 1783, and Cort improved the furnace and patented his version the following year. His method initially worked best with white cast iron, while later refinements helped make the process more commercially practical.

Puddling is often confused with galvanizing, case hardening, or electroplating. Those are surface-treatment or finishing processes; puddling was a primary iron-refining operation that changed cast iron into wrought iron.