Note 7 — Chapter IV · ON THE MANUFACTURE OF IRON FOR GUN BARRELS.
Reading edition
The fine quality of the Indian steel is generally acknowledged. The iron is first obtained by smelting, in small quantities, the wootz-ore, or the magnetic oxide of iron, which it found combined with about 42 per cent. of quartz; the yield being, out of 100 parts of ore, only 15 parts of metal: but this is of the finest character.
The process by which the iron is converted into steel is as follows, and fully accounts for that peculiar quality for which the Indian steel is valued.
The iron is cut into pieces and packed closely in a crucible of clay, containing about 1 lb. only of the iron, mixed with a tenth part of dried wood cut small, the whole covered over with green leaves. The crucible is then stopped, by covering the mouth with tempered clay, so as to effectually exclude the air. After a time that is, as soon as the clay-plugs are sufficiently hard, from twenty to thirty of the crucibles are built up in an arched form placed in a small blast furnace, and kept covered with charcoal; thus being subjected to the heat of the furnace for two or three hours. The process is then complete.
As soon as the crucibles are cool, they are broken open and the cakes of steel are found rounded at the bottom.
The top of the cakes should be found covered with striæ, radiating from a centre, and be free from holes or rough projections. If the cakes are honeycombed, the process has been imperfect and incomplete. When re-melted and tilted into rods, a very superior article has been the result.
The natives prepare the cakes for being drawn into bars, by annealing them for several hours in a small charcoal furnace, excited by bellows; the current of air being made to play upon the cakes while turned over before it, whereby a portion of the combined carbon is dissipated and the steel probably softened: without which operation the cakes would break in drawing them. They are drawn by a hammer of only a very few pounds weight, but the repeated hammering greatly tends to the production of a highly condensed and perfect article.