An Encyclopaedia of Indian Archaeology v1.c21.s7.4

v1.c21.s7.4

The use of this type of small, crucible-shaped, clay-lined, forced-draught furnace, which probably began in the Chalcolithic period in India, has continued to the present day. [For furnaces of the historical period see UJJAIN, NĀLANDĀ.] Many metal-working tribes like the Loharia and Agaria use it for smelting iron. They charge the furnace with crushed haematite and charcoal (2 to 3 cm cube), which they push into the furnace in small quantities at a time from the top as required according to the colour of the flame. About 20 kg of ore and 20 kg of charcoal are added in about four hours and finally topped with excess charcoal. When the charge is smelted the flame becomes luminous; the bellows are stopped and the slag outlet opened. A spongy bloom of wrought iron, about 1 kg in weight, is formed at the bottom of the furnace. It is taken out by breaking the furnace. It is repeatedly heated to redness in an open hearth and forged on an anvil in front of the hearth to separate out the adhering slag. Simultaneously the surface of the metal is carburized and case-hardened. It is further forged to shape the metal into desired objects.