There are two possibilities for creating a bronze statue using the lost wax method:
1\ One works directly in the wax
This method is, however, somewhat limited as far as details are concerned, and does require an amount of dexterity and experience with the handling of the wax. The advantage, however, is that one does not have to make a mould, something that saves a great deal of time.
2\ One first models a statue in clay
Once the statue has been modeled, a mould is made. In certain cases one can make complete plaster moulds, but in most cases one must make a silicone mould provided with a plaster supporting mould. A mould consists of at least two parts, because one must be able to pull the mould open or one cannot remove the wax sculpture from the mould. Once the mould has been made, the wax is poured into the different parts of the mould to a certain thickness of at least 3 mm depending on the size of the sculpture. The mould parts are placed against each other and the seams are sealed. The mould is then opened and the seams are worked away. One now has a finished wax sculpture.
If one uses method 1 or 2, in any event pouring ducts and air ducts must be used. A more primitive method suitable for smaller sculptures as described below requires more pouring ducts and certainly more air ducts. This method does require much more finishing work.
Description of the more primitive method
Once the wax sculpture has been provided with the necessary pouring and air ducts, a heat-resistant mould (embedded mass) is made completely around the wax sculpture. With hollow sculptures, an inner mould (embedded mass) must first also be used. This mould is held fast by inserting steel pins through the mass and the wax. The reason is that the bronze may not be too thick or shrinkage will occur. Once the mould has dried hard, the wax is heated very slowly in an oven (15 to 20 hours, sometimes longer depending on the size of the mould). During the first three hours, one may not use a temperature higher than 100° to 150° degrees Celsius. The temperature is then slowly increased to 600° to 700°C. During this process, the wax melts and vaporises or is collected.
After cooling down, the mould (moulds) is/are placed in a bin with sand. This is to give the mould extra support, and for safety reasons where if the mould breaks during casting, the liquid bronze can be collected in the sand. The bronze is now melted in a crucible heated in an oven to a temperature of 1200°C by a burner using propane gas. The temperature is measured using a pyrometer. After reaching the correct temperature, the bronze is poured into the moulds. Floating slag is scooped off so that it does not enter the moulds. The mould (moulds) is/are allowed to cool and carefully opened (chipped away). Once the mould has been fully removed, you have a bronze sculpture with the pouring and air ducts attached. The pouring ducts and air ducts are ground off and the sculpture is cleaned up. A patina layer is then applied, and afterwards a wax coat to protect the patina. The sculpture is then polished.