PSM V38 D165 Vertical section of a 17th and 18th century blast furnace

Cold blast, in ironmaking, refers to a

metallurgical furnace A metallurgical furnace, often simply referred to as a furnace when the context is known, is an industrial furnace used to heat, melt, or otherwise process metals. Furnaces have been a central piece of equipment throughout the history of metallurg ...

where air is not preheated before being blown into the furnace. This represents the earliest stage in the development of ironmaking. Until the 1820s, the use of cold air was thought to be preferable to hot air for the production of high-quality iron; this effect was due to the reduced moisture in cool winter air. The discovery by

James Beaumont Neilson James Beaumont Neilson (22 June 1792 – 18 January 1865) was a British inventor whose hot-blast process greatly increased the efficiency of smelting iron. Life He was the son of the engineer Walter Neilson, a millwright and later engine ...

in about 1825 of the beneficial effects of the

hot blast Hot blast is the preheated air blown into a blast furnace or other metallurgical process. This technology, which considerably reduces the fuel consumed, was one of the most important technologies developed during the Industrial Revolution. Hot b ...

led to the rapid obsolescence of cold blast ironworks in

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

, where hot blast was in general use by 1835. Cold blast ironworks survived longer in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, but the use of hot blast as a method of smelting iron with

anthracite Anthracite, also known as hard coal and black coal, is a hard, compact variety of coal that has a lustre (mineralogy)#Submetallic lustre, submetallic lustre. It has the highest carbon content, the fewest impurities, and the highest energy densit ...

was introduced in 1836, and the increasing US production of coke gradually drove out the cold blast furnaces. However, one of the last known operating cold blast

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...

furnaces, Pleasant (formerly Eagle) Furnace, in Curtin, Pennsylvania did not close until 1921.

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* {{Iron and steel production Blast furnaces Steelmaking