The art of inlaying silver in a dark metal base which is an alloy of zinc and copper originated in Bidar, Hyderabad, and is called Bidri.
Castor Oil is mixed in clay to make a mould. A molten alloy of zinc and copper is poured into the mould. The surface to be adorned is smoothened and the pattern to be inlaid is chiseled out with a metal stylus. The craftsman hammers fine silver wire into the engraved area. On buffing, the entire surface, including the silver inlay, glows evenly. You cannot see the pattern as yet. A paste made from soil, ammonium chloride and water is rubbed onto the heated surface and when rinsed off, it reveals the pattern as the background darkens. Finally oil is rubbed to deepen the background and show off the polished silver in contrast.