There are broadly 10 stages in the making of an icon by solid casting.
Before a craftsmen starts working on an icon, he takes note of the 'talas' to be used in the making of it as laid down in the shilpashastras. He then takes a narrow ribbon of coconut leaf-odiolai- cut to the given length of the icon and by folding it at different lengths marks the prescribed proportions for the different parts of the image.
The second stage is the preparation of wax for making the karavu(wax model). Pure beeswax, dammer(resin from the tree damara orientalis) and groundnut oil are measured out in the proportion 4:4:1 dammer is first powdered and mixed with groundnut oil and heated till it forms a thick liquid. Then scraps of beeswax are added to it and stirred with a stick till it liquefies and is well mixed. This liquid is then sieved into cold water through a fine metal sieve or a coarse woven cloth. The wax immediately solidifies in cold water and is ready for use.
Next is a crucial stage where the craftsman's creativity is most apparent because the excellence of the icon depends of the wax model. The wax model is prepared out of the solid wax which is made malleable by warming it over a charcoal brazier. Body, head and limbs are modelled separately, at first crudely by hand and then shaped and sculpted using the spatula, knife and scraper. The different parts thus modelled are then joined together with the help of a heated soldering iron. In the case of small icons, the wax pedestal is joined and final touches given and measurements verified at this stage. In the case of larger icons the wax pedestal is modelled separately.
A few cross strapping, made with prepared wax, are also fixed on the wax model, to strengthen the model as well as to facilitate easy flow of the molten metal to the various parts. A wax rod ending in a funnel shaped flange, known as the wax runner is also fixed to the base of the wax model. Later on when the mould is heated and the wax is drained out, this serves as ingress for the molten metal.
In this stage, locally known as 'munkettal', the wax model is coated with layers of clay-three layers for small images and more in the case of larger ones. A different type of clay is used for each layer. The first coating is of fine loam, locally known as 'vandal mun' collected from the bed of the Cauvery River. This loam is finely ground along with charred paddy husk and mixed with cow dung. The wax model is coated with this thick mixture to about 1/8 inch thickness.
While applying the clay coating the wax model is kept over a piece of paper on its side. In the case of larger images. The model is kept over sand so that it is not deformed by the pressure of its weight. After the clay coating is dry, the model is turned, and the other side coated is dry, the model is turned, and the other side coated with clay. Drying is done either under mild sun or in the shade so that the wax model does not melt.
The first coating is important in two ways. It gives protection to the wax model and more importantly it conveys the contours of the model to the model to the cast image. Therefore no space on the wax model should be left uncovered expect the wax runner which has to function as an outlet for the melted wax and an inlet for the molten metal when casting takes place. There should also be no air bubbles on the surface of the clay coating. The inner surface of the coating receives the impress of the wax model and preserves it; it also receives the molten metal and gives it shape. It is therefore necessary that the first coating should be very fine in texture so that the minutes detail of the wax model is faithfully preserved. The clay mould should also have enough elasticity to withstand the heat of the molten metal when it is poured into it.
The second clay coating applied over the first, is a mixture (locally called ‘padimun’) of clay from paddy fields and the sand in the proportion 1:2, the clay and the sand being first thoroughly mixed with water to form a paste. The paste is said to be ready for use when it gives a rustle sound when squeezed. The thickness of this coating varies from ½″ to 2″ according to the size of the image. After the second coating is dry, a third thicker coating of rough sand and clay paste is applied.
If necessary, a fourth coating is given. If the image is large the mould is re-enforced with iron rods and wires lest the mould gives way when the hot molten metal is poured in. some craftsmen still follow the old method of using broken earthenware instead of wires and rods as reinforcement.
The finished mould, with the wax model inside it, is heated over an open ground oven fuelled by cow dung cakes. The wax model melts in the heat and the wax drains out through the runner into a small pit. It can be used again later after removing foreign matter etc. While the wax model and clay mould are getting ready, the preparation of metal alloy also gets under way. The number and kinds of metals to be used for casting of scared images Re prescribed in the silpasastras. Formerly these consisted of five metals (panchaloha) considered to be highly auspicious - copper, silver, gold, brass and iron or lead. Gradually however, silver and gold stopped being used because of thhier high cost. But icons for worship may still be cast in the original five metals if specially commissioned.
Ordinarily, the images are cast by alloying copper, brass and iron in the ratio 29: 2: 1 respectively. Sometimes in addition to these three metals, tin of the same quantity as lead is also mixed in the alloy. Sometimes, the craftsmen may deviate, within limits from the normal proportions in the light of their own experiences to them if copper alone is used for casting the icon it will not give a lasting shine nor will it melt quickly. Addition of a little brass considerably lowers the melting point but at the same time gives a good and lasting shine to the icon. The craftsmen also think that by adding a little lead the molten metal can be made more malleable thus facilitating chiselling and engraving. The weight of the metal alloy is generally 8 times the weight of the wax model. The metals used are either solid pieces or scrap from broken utensils. Good craftsmen do not like to use scrap because it does not give a good shine.
To make the alloy, the required quantity of metal scraps is melted in a pyrite crucible placed in a pit furnace fuelled with coke and the process takes about 4-5 hours.
While the alloy is being prepared the mould is heated re hot, as otherwise the heat of the molten metal flowing into the hollow clay mould could cause it to explode. The heating of the hollow mould serves two other purposes as well - it removes air bubbles from inside the cavity and it prevents the molten metal from cooling down suddenly resulting in a uneven surface.
When the mould is heated to the required temperature and the alloy is ready, it is removed from the hearth and firmly planted on even ground with the runner facing upwards.
Now, a metal ring fitted with cloth known as 'mugatuni' is placed over the opening on top and the molten metal is poured into it in a thin and even stream does not cover more than half the opening so that displaced air from the hollow cavity can escape. The metal ring fitted aat the top gives support to the crucible from which molten metal is poured and also prevents overflow.
When pouring the metal, a piece of sacking is used to cover the mouth of the crucible. This prevents any floating impurities in the molten metal from flowing into the mould.
The mould is now left to cool down gradually. Normally this takes a day. But if the mould has to be broken early, it is doused with water, 2-3 hours after the casting.
When the mould has cooled down sufficiently it is broken open and the metal image exposed. The iron rods and wires used as re-enforcements are carefully retrieved to be used again.
To the craftsman, the breaking of the mould to bring out the metal image is of great significance. To them the image is not merely an object but a transcendental entity. The portion of the mould holding the head is always broken open first.
The clay sticking to the icon is first scraped off. Then a sharp chisel called a 'borai' is used to hammer out any connecting rods used as support for very complicated castings. Next uneven surfaces on the cast image are smoothened and finely chiselled to recapture the contours and details of the original wax model. Engraving is done to provide details of dress and ornaments, and to make the image perfect in every way. The surface of the image is then rubbed smooth with fine grade emery paper. It is then cleaned with tamarind and soap nut water and scrubbed with a wire brush. And finally it is given a last brisk brushing with polishing sand and water.
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