Puddling and rolling

node · earth · Fontley, Hampshire; then the ironmaking districts

The second half of the iron problem, solved in the mid-1780s by patents taken out by Henry Cort. Puddling decarburises pig iron into malleable wrought iron in a reverberatory furnace, where the flame is deflected onto the charge from the roof so that the coal never touches the metal and cannot contaminate it; the puddler stirs the pasty mass with a rabble until the iron balls up. Grooved rolls then squeeze the bloom into bar in minutes rather than the hours a forge hammer took. Together they multiplied output per worker several times over and completed the removal of charcoal from ironmaking. The origins of the process are contested. Puddling in some form was described before Cort, and a 2023 paper in History and Technology argued that his method derived from techniques developed by enslaved and free Black metallurgists at a Jamaican foundry — a claim that provoked substantial published criticism from historians of technology and remains disputed. The dispute is recorded here rather than resolved.