Minerals and Metals in Ancient India v1.c11.s7.1

v1.c11.s7.1

After getting the raw metals, the next step is the manufacture of objects from these metals. So the question automatically arises that how those chalcolithic objects were made? It is found that the common metals in the Indus Valley are copper and bronze. In the case of the copper objects, the process was a simple one i.e., to raise all the copper vessels from the sheet metal as their shapes are simple. But in the case of the bronze vessels there are several methods which could have been employed. Firstly, beating them out of sheet bronze, which however would call for constant annealing to prevent the metal from cracking, and the second process is called cire perdue. This process is exceedingly difficult for large and thin castings owing to the risk of flaws and crevices that would render the vessel made in this way non-watertight. The varying thickness of the metal of some of the bronze vessel suggests that the cire perdue process was used; on the other hand it may also be possible that this inequality arose on account of corrosion. Another probable cause for this varying thickness may be that the bronze vessels were raised from sheet metal which being unrolled, would in the first place not be of equal thickness throughout. (M-II,488)