The lost-wax process, also known as Cire-perdu, is a technique used for making objects of metal, especially in Himachal Pradesh, Odisha, Bihar, Madhya Pradesh, and West Bengal. In each region, a slightly different technique is used.
The lost-wax process involves several different steps. First, a wax model of the image is made by the hand of pure beeswax that has first been melted over an open fire, and then strained through a fine cloth into a basin of cold water. Here it resolidifies immediately. It is then pressed through a pichki or pharni which squeezes the wax into a noodle-like shape. These wax wires are then wound around to the shape of the entire image.
The image is now covered with a thick coating of paste, made of equal parts of clay, sand, and cow dung. Into an opening on one side, a clay pot is fixed. In this molten metal is poured. The weight of the metal to be used is ten times that of wax. (The wax is weighed before starting the entire process.) This metal is largely scrap metal from broken pots and pans. While the molten metal is poured in the clay pot, the clay-plastered model is exposed to firing. As the wax inside melts, the metal flows down the channel and takes on the shape of the wax image. The firing process is carried out almost like a religious ritual and all the steps take place in dead silence. The image is later chiseled with files to smoothen it and give it a finish.
Casting a bronze image is a painstaking task and demands a high degree of skill. Sometimes an alloy of five metals – gold, silver, copper, brass and lead – is used to cast bronze images.