The Simplified version.
Once the silicon rubber mould has been taken from the original (Plasticine) sculpture, a hollow wax replica is created from this mould. Below, the rubber mould has been opened into its two halves so that the insides can be seen.
Strands of wax (sprues) are attached to various parts of the wax replica in order to leave channels within the final, heat proof, mould. These channels allow better bronze access to confined spaces and let gases escape from, areas that they would otherwise be trapped in, thus creating holes in the final bronze sculpture.
This wax, complete with any sprues, has a heat proof, ceramic case formed both inside and out (with the inside, or core, held on place with pins pushed through the walls of the hollow wax replica). The wax is melted out of the ceramic case (hence the name “lost wax process“), leaving a void within the ceramic casing exactly the same shape as the wax replica was.
This casing is then heated to around 600 degrees C. Molten bronze (at around 1200 C) is poured into this ceramic casing and once cooled the bronze is knocked out of the ceramic, and any sprues and excess bronze is ground off and these areas made good by a skilled bronze fettler.
The photograph shown right is of the gun dog bust after casting and fettling has taken place.
This is the colour of “raw bronze”. Most bronzes are treated with chemicals and maybe heat as well to produce a variety of different colours and other effects. This is referred to as the patination.
As this sculpture was of a black, flat coated retriever, it was fitting that it would be given a black bronze finish.
This was achieved by the skilled hands of the foundries patineur, a blow torch and a secret concentration of a sulfurated potash solution (see photo at left).
Once patination is complete, but while the bronze is still warm to the touch, wax is applied to “fix” the patina. When completely cool, this surface is then buffed to a soft sheen.
The video below shows the completed sculpture after the granite base has been fitted. For information on commissioning a bronze of your own, please visit my Commissions page.