History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c37.53

c37.53

An alloy of considerable interest, produced in India since the Mogul period, has been named *bidery*, from Bider, a town 60 miles north-west of Hyderabad. It has a blackish colour and is composed of copper, lead and tin (8 : 2 : 1). These are melted together, mixed with spelter or zinc (16 parts for every 3 parts of the alloy) and the mixture melted again. It is then dipped into a solution of sal-ammoniac, saltpetre, common salt and blue vitriol, when the surface of the alloy turns black. According to another process zinc, copper and lead (30 : 1 : 1 approx.) are melted together, and a mixture of resin and beeswax added to the mass in the crucible to prevent calcination. It was then poured into a mould made of baked clay. The article was finally turned in a lathe. Artists then inlay flowers and other ornaments of silver or gold. The article is first rubbed over with sulphate of copper and water to give the surface a blackish colour, which makes it easier for the artist to distinguish the figure drawn by him. The cavities are then filled up with small plates of silver which adhere firmly to the *bidery*. It is then polished and stained. Vases, basins, cups, etc., are made of it. Some *bidery* is also made in the N. W. India and some in Bengal.