Bidri craft Raw Materials:
The significance of the craft lies not only in its beauty, history, and production technique but also in a special ingredient- the soil from the Bidar Fort - bidri matti. This black soil is an important input for Bidri work as it has special chemical properties; the soil has been away from sunlight and rain for hundreds of years and is used as an oxidizing agent. No one really knows what makes this soil unique. The Bidri craftsmen have varied theories – one suggested that back in the Sultans’ days, copper coins were made in a section of the Fort. Powdered metal seeped down to the soil, giving it its oxidizing property over the years. Another artisan claims it is because weapons were stored underground in the fort. Resins and castor oil are the other raw materials. The forensic report says the soil consist of salted chloride and calcium which gives a black color to the bidri handicraft.
The basic metal of this craft is an alloy of Zinc and Copper mixed in the proportion of 16:1. The melting temperature of this metal alloy is 800°F. Such an alloy is known as the ‘white alloy’ because the ratio of copper used is very little. The required base turns jet black when subjected to the ultimate oxidization process.