History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c15.s2.46

c15.s2.46

Iron produced in ancient India was mostly wrought iron. For, with charcoal as fuel usually employed, the temperature inside the furnace could not have been high enough to melt the metal and thus to ensure absorption of carbon for the production of cast iron. At the low temperature thus prevailing in the furnace, the whole of the ore used, however, was never completely reduced, and a considerable portion escaped reduction. The metal was obtained in the form of a pasty mass or bloom, which was then brought under the hammer to be shaped into bars. The furnace employed was obviously of a very crude type, probably a large hole in the ground over which was built up a circular chimney or shaft with sand and clay; air might be forced into the furnace from the bottom by means of a hand bellow made of goat, sheep or buffalo skin furnished with bamboo tubes. The furnace might have been provided with two openings at the bottom, one for the blast of air and the other for the exit of the slag. Ore and charcoal were piled up in the furnace to start with.