History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c11.s1.t1.6

v1.c11.s1.t1.6

Pure copper is not a hard metal, but it can be made harder through beating (cold work). Too much cold work, however, makes the edge brittle and it then requires heating (annealing) to make it ductile again. Alloying copper with arsenic or tin increases its hardness considerably, and today we know that copper should be alloyed with up to 4-5% arsenic and 8-12% tin for maximal ductility and hardness. We have now more than 200 analyses of Harappan artifacts (Agrawal et al., 1978b), which indicates that only 23% were alloyed with tin, 12% with arsenic, 8% with lead, besides a smaller percentage with an admixture of these elements. It should be noted that the Harappans used both Sn and As alloying and the Chalcolithic cultures exclusively tin alloying (*Fig.5*). In an effort to locate copper artifacts, we find a hatchet at Khurdi (*Fig.6*) similar to one found at Kalibangan. As regards Fig. 2 Main Harappan metal artifact repertoire