The making process of Bronze Idols goes through following processes:
The idol is modeled from a molten wax mixture in the required size and proportions. Kunguliam (resin) and mezhugu (paraffin wax) are mixed with an addition of kadalaiennai (groundnut oil). The mixture is heated on a stove and allowed to cool to a consistency and temperature that is comfortable to handle and shape. Torso, hands, legs and the seating pedestal are fashioned from wax individually and then put together by heating and fixing. The wax model is placed on a wooden plank so that the center of gravity can be mapped out accurately. Weapons and accessories prescribed for the idol are fashioned and placed suitably. Using softer and finer wax, the idol is adorned with jewelry. The form is smoothened and allowed to dry. Once dry, the wax form is weighed. The weight of metal required for casting is ten times the weight of wax required to make the model.
Solid and Hollow Casting:
A sculpture that is metal all through is termed as solid cast. Solid casting is practiced for temple sculptures. A hollow cast is made with a clay-fiber core and a cladding of cast metal on top. Decorative pieces, to reduce consumption of metal and minimize weight are cast with a clay and jute fiber core.
Mould Making (Koaruv):
The idol is placed on a bed of sand atop a cloth face up. A layer of vandal mann (fine grained clay) is applied on the wax idol. Care is taken to cover every nook and corner of the wax idol/model. Vandal mann is highly impressionable and captures the minutest of details of the wax model. A mixture of kali mann (alluvial soil) and manal (river sand) mixed in 1:3 proportions is applied over this layer. The mud sheath on the face side is allowed to dry for about four days. The idol is turned and channels called runners made of wax are affixed to the wax form. These channels act as outlets of wax and inlets for molten metal later. Two channels are placed side by side. This side of the idol is covered in vandal mann, kali mann and manal and allowed to dry for four days. A metal wire is wound around the mould to keep the casing intact. For multiple castings of the same form, plaster of Paris moulds are made instead of mud moulds. These can be used for casting about hundred times before they wear out.
The mould is placed with the channels facing downwards and heated. The wax melts and trickles down the channels. As the wax is removed, a negative space is created within the mould.
Baking the Mould (Karuvu Pazhukardhu):
The mould is then inspected for fissures. Cracks are sealed with a coat of mud and it is propped on bricks. Coal, firewood and dung cakes are used to create an open furnace around the mud shell. The sculptors know when the mould is baked right through by the density of emitted smoke. On baking, the shell takes on the colour of a baby rat. In case of large idols, the positioning of the mould for the baking process is vital. The mold is placed such that it can be flipped into a pit adjacent to it with the channels facing upwards using minimum energy and force. The mould is allowed to settle for a few hours before it is moved into the pit. In the case of solid casting, it is allowed to cool down completely before metal is poured into the cavity. For hollow casting, the mould is maintained in a similar temperature to that of melting metal for a smooth casting. In a corner of the workspace, ash from the baking process is collected. In the past, farmers collected the ash to use in their fields as manure. Ash was also used for washing utensils before the advent of dish-washing soaps.
A rectangular pit with a metal grate and a side inlet for air is used as a furnace for heating metal. Two pots can be placed inside the pit. A small amount of damp mud keeps in place two bricks placed in the pit. The bricks are dusted with sand to prevent the pots from sticking when placed atop. On top of this makeshift stand, pots are placed. Metals are weighed and added to the pot. Copper (85%), zinc (10%) along with tin and lead are used to make the idols at Swamimalai. Coal is shoveled all around the pots and a few dried dung cakes are lit. An electrical air blower strokes the fire. The pots are covered with stone domes and the metal pieces are allowed to melt. Metal is constantly added in small quantities till the required weight is obtained.
Burying the mold: A pit of the size of the mould is made close to the baking and metal melting area. The mould is placed in the pit at an angle with the channels at ground level. The pit is then packed with mud. The moulds have a tendency of expanding slightly when metal is being poured in. Burying of the mould ensures that the expansion is countered and the dense packing of mud stems fissures and prevents leaks.
As soon as the metal has liquefied, the heating pots are lifted and the red hot metal is poured through one of the channels. Air escapes through the other channel. The metal is poured in continuously till the inside cavity has filled. The cast metal is allowed to cool after which the mould is broken.
Breaking the Mould:
The mould is unearthed and the metal bindings clipped. The baked mud casing is cracked open at the spot where the head of the idol lies. Then the rest of the mold is broken open and cleaned with a brush. The channels are sawed off and the idol is cleaned.
Fine details are revisited with a chisel. The idol is usually held with the feet and chiseled to sculpt the fine details. About ten percent of the metal mass gets chipped off while chiseling. Chipped fragments are collected for use in further castings. For the reason that sharp facial features do not get damaged while handling the piece, the face is detailed last.
The idols are cleaned with tamarind water and soap nut stone and scrubbed with charcoal. They are then buffed using electrical polishing machines. Some pieces are treated with chemicals to create a patina.
Lost Wax Casting Process:
Baking the Mould:
Melting the Metal:
Breaking the Mould:
Detailing and Polishing: