Dhokra - a non–ferrous metal is made using ‘Lost Wax Technique’. There are two types of Lost Wax Techniques:
• Solid casting - Where a solid piece of wax is used to create the mould instead of a clay core.
• Hollow casting - It is more traditional method which involves the use of the clay core.
The Process followed currently for making products is discussed as below:
A basic model is prepared by using black soil mixed with rice husk in appropriate ratio. Soft pliable dough is made by adding water in it. A basic model of craft is made and dried in the sun.
For second layer, cleaned riverside soil is used. A powder of dung and water is added and mixed thoroughly for smooth dough. It applied all over the dry model & again left to dry in the sun.
The hard & dry model is filed & shaped with metal files to achieve a proper shape. When the model is ready, it is scrubbed all over with hands to remove dust. A very thin semi liquid layer of black soil is applied over the model and is left to dry.
The bean leaves are then crushed by rubbing them between the hands and applied over the model until it looks green. The purpose of applying green liquid to model is to prevent the soil from sticking to the model. The model is left to dry again in the sun.
Thin wax threads are then wrapped closely around the model. The wax threads are made using hand-held press, which is also known as phichki-pharni in Bastar.
A layer of riverside soil & powdered wood coal is applied over the model. A chamber is made at the bottom of the model, where the liquid metal has to be poured for casting. Final layer of termite soil is applied by adding bigger channel. This channel is added to the earlier chamber made at the bottom & covered with termite soil mixture to make the passage ready & dried.
The casting process starts with the preparation of furnace for firing & casting. The model is made wet with liquid mud and kept on the burning coals for firing. It is kept erect by giving support with wooden sticks.
Another furnace is made for melting metal pieces which are then placed in a vessel. This vessel is placed over burning coal. The fire is blown continuously. When the model in the first furnace turns red, it is ready for casting.
The ready-fired model is lifted gently & brought near the vessel. The liquid bell metal starts emitting green blue flames, which is an indicator of the ideal temperature of its liquid state.
It is then poured in the channel, which is made at the bottom by keeping model upside down. The wax inside the model is replaced by molten metal poured through funnel. Then model is left to cool.
After cooling, the outer model is broken gently with a wooden mallet or small hammer. The actual shape of the craft is then rubbed & cleaned.