Puddling is the process of converting pig iron to bar (wrought) iron in a coal fired reverberatory furnace. It was developed in England during the 1780s. The molten pig iron was stirred in a reverberatory furnace, in an oxidizing environment to burn the carbon, resulting in wrought iron. [1] .

Puddling was the first successful process for making malleable iron from pig iron without using charcoal. Unlike in the Finery the iron was not in direct contact with the fuel of a puddling furnace, only with the hot gases from it. This helped reduce the amount of impurities in the finished iron.

Puddling steel is a technique with which pig iron in semi-melting state can be puddled and decarbonized into steel. It is a steelmaking technique in ancient China. During the process, pig iron is first heated in the air to the semi-melting state.

Throughout most of the 19th century, the process of choice in the west for producing wrought iron and steel was “puddling” of cast iron. A major development of the process, “wet puddling”, became wide-spread commercially beginning in 1830.

The original dry puddling process was replaced beginning in 1830 by wet puddling, which was radically different in terms of the key chemical reactions involved, the thermal behaviour of the melt, the speed of the process and the quality and consistency of the resulting product.