The lost-wax process, also known as cire-perdue, is a metal casting method involving the use of a wax model to create a mold into which molten metal is poured.
This technique has a rich history dating back to the 3rd millennium BC and has undergone minimal changes over the centuries.
Found on every continent except Australia, it continues to be a significant method in metal casting.
To cast a clay model in bronze using the lost-wax process, the following steps are taken:
- Mold Creation: A mold is made from the original clay model. Inside this negative mold, melted wax is brushed to achieve the desired thickness for the final bronze casting.
- Wax Shell: After removing the mold, the resulting wax shell is filled with a heat-resistant mixture. This shell now encapsulates the form of the original model.
- Wax Tubes: Wax tubes are attached to the outer surface of the wax shell. These tubes serve two essential purposes: they provide pathways for pouring molten bronze into the mold during casting, and they act as vents for the noxious gases produced during the process. The artist may also adjust or modify the wax shell at this stage.
- Securing the Core: Metal pins are driven through the wax shell into the heat-resistant core to ensure it remains in place.
- Plaster Coating: The prepared wax shell is then coated with multiple layers of heat-resistant plaster. The entire assembly is inverted and placed in an oven.
- Wax Removal: As the plaster heats up, the wax within the shell melts and flows out through the ducts created by the wax tubes. This leaves behind an empty space within the plaster mold in the precise shape of the original model.
- Bronze Pouring: The plaster mold, now devoid of wax, is encased in sand to provide support. Molten bronze is poured into the mold through the ducts created by the wax tubes, filling the void left by the wax.
- Cooling and Removal: After the bronze has cooled and solidified, the outer plaster shell and the heat-resistant core are removed. The resulting bronze casting is then subjected to any necessary finishing touches.
The lost-wax process is renowned for its ability to replicate intricate details and achieve a high level of precision in metal castings.
It has been used to create a wide range of objects and artworks throughout history, reflecting its enduring significance in the world of metalworking and artistry.