History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t4.104

v1.c13.s2.t4.104

After the hot sponge (weighing about 3-9 kg) was consolidated into a semi-porous mass by forging and squeezing out the molten slag (Fe₂ SiO₄) it was further refined to remove the remaining FeO and Fe₂SiO₄ slag and at the same time increase the density of the solid iron block or rod. For this the block was repeatedly heated in a forge hearth and SiO₂ was sprinkled on it so that remaining FeO may get converted into Fe₂SiO₄ or FeO.Fe₂SiO₄ Eutectic (M.P. 1170°C) i.e. fluid slag and flow out of the semisolid mass.