History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t4.102

v1.c13.s2.t4.102

(v) *Handling of sponge*: The hot iron bloom taken out of the furnace was hammered on stone anvil to squeeze out the liquid slag as much as possible before it is solidified. This porous sponge iron block was repeatedly heated in a forge hearth to reforge and refine the wrought iron thus produced. The refining treatment can be called the secondary treatment.