Last and most widespread of the ways to produce wrought Iron from pig Iron. First devised by Henry Cort in 1784, but later revised by Joseph Hall in 1816.

Solid iron, be it fresh pig iron or scrap cast iron, was first melted and then refined. Once the iron was molten in the bottom of the hearth, it was stirred with a long pole. This brought the carbon in contact with the air where it burn off. However as the carbon content reduced, the melting point increased and the iron became a lump of sticky wrought Iron. The process was sometime known as 'pig boiling' as the iron tended to bubble as the carbon was removed.

Hammering and rolling followed puddling in order firstly drive out the slag, weld the iron into a homogeneous lump and lastly produce a saleable product. Puddling had to take place in a reverberatory furnace in order to avoid contamination of the Iron.