Metal Icons of Thanjavur
The Metal:
Generally, an alloy of copper, brass and lead is used. Sometimes gold and silver are also added as per the demand of the customer. Before beginning the process, the experts take the weight of the wax model. Brass and copper should be taken ten times that of wax, silver twelve times; and gold sixteen times.
Copper by itself would not give a good colour, neither would it melt easily nor run smoothly. The addition of brass to copper gives better colour and lowers its melting point. But an alloy of brass and copper would not run easily and it would be difficult to work on it with a hammer and chisels. Therefore a little lead is added to the alloy. Lead smoothens the pour and imparts flexibility called “Nyppu” in Tamil to the metallic surface, rendering it easy to work on with a chisel and hammer. Normally the alloy contains copper, brass and leads in the ratio of 20:5:1.
Ceramic crucibles: Used for melting metals.
The furnace:
The furnace is a rectangular pit, 5 feet* 1 ½ feet and 2 feet deep, with a brick lining and brick flooring.
The fuel:
Coke for melting the metal. Dung cakes and firewood for heating the mould.
Prongs:
Used for lifting the crucibles out of the furnace and for pouring the Metal into the mould.
Heating of the Mould:
The mould is heated till it becomes cherry red and is then buried in the earth up to the mouth of the orifice so that it remains in an upright position when hot liquid metal is poured into it. After the hot liquid metal is poured into the mould, the mould is then allowed to cool gradually. Then the binding wire is cut, the rods if any are removed and the mould is broken open when the metal image is revealed.
• Materials used for finishing:
• Hammers
• Chisels
• Files
• The seevuli
