Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c24.9

c24.9

7. The ‘refined’ cast iron, now termed ‘fine metal’, is then exposed in a reverberatory furnace, called the ‘puddling furnace’, to the action of the flame of a large coal fire, by which it is first partially melted, then falls into a coarse powder; and on being stirred up and presented to the flame, becomes at last adhesive and tenacious. It is then formed into large balls, and after receiving a few blows from a large hammer to consolidate it, is passed between rollers which squeeze out much of the impurities, and form it into ‘mill bar iron’. This is however too impure for use, and it is necessary to cut the rough bars into pieces and to weld them together afresh, in a ‘reheating furnace’, and expose them to another rolling, and even to repeat the operation a third time, before good tough bar iron is produced. In the ‘puddling furnace’ about a ton of coals is expended to each ton of ‘fine metal’, and in the ‘reheating furnace’, about 150 pounds more are expended; and in each operation a loss of about ten per cent takes place in the weight of metal operated upon.