History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t3.66

v1.c13.s2.t3.66

Copper, a brick red coloured metal has a melting point of 1083°C and it is very ductile in nature. This can be easily cold or hot worked to give any shape like rod, plate, wire and sheet etc. Hence, it has been extensively used in the past for the manufacture of domestic utensils, jewellery as well as for covering the wooden surface and engraving it for decoration and preservation of wood pannelling. The work hardening effect can be easily removed by annealing at 700-800°C in cowdung fire to produce metal having stressfree recrystalised grain having high ductility. The archaeological evidences have shown that this metal was shaped into various objects by casting into stone and clay moulds, hot and cold forging and soldering or rivetting to join two metal pieces. The ancient craftsmen had a flare to produce beautiful designs on the copper objects by embossing, engraving and gem setting. Beautiful objects having carvings inlayed with Gold and Silver wire and hot enamelled have been also found in latter stages. Copper being soft metal the sharp edge of the hunting tools and war weapons were hardened by cold working till the technology of production of bronze and Cu-As alloys were developed, which were much harder than the cold worked copper. On polishing the surface of copper could be given a highly shining polished finish which was being used as a mirror in the royal families. The Gold coating of copper objects by the process of amalgamation was also in the practice to produce various decorative cheap articles made from copper but having a golden finish.