BRONZE WORK


 

Alain Choisnet sculpts his models mainly in clay. A sculpture may require 100 to 150 hours of work until finished. Then he entrusts it to an art founder who will turn it into bronze. Several professionals are involved in this realization. In constant quest for the best quality, Alain intervenes at different stages of the process in addition to the care provided by the foundry.

 

The technique of "lost wax" casting

Used for over 5000 years, bronze is an alloy of copper and tin. Here are the main steps of the so-called "lost wax" technique that allows you to reproduce bronze objects and can vary slightly from one foundry to another. This video illustrates these different phases.

 

Moldmaking

A first two-part silicone impression is made directly on the clay (sometimes the sculpture is cut and its different parts are molded separately). Plaster is then applied to the silicone to support it so that it does not deform. The quality of the outer mold in plaster and the silicone mould are essential because it will reproduce faithfully all copies of the original model (the 8 copies + 4 artists' proofs).

 

Wax work

The clay is removed from the mold (it can be used again to create new models). Hot wax is stamped with a brush inside the mold (to avoid air bubbles), then the two parts are assembled. The entire mold is filled with molten wax and let it cool until a desired thickness has set on the surface of the mould. After this the rest of the wax is poured out again, the mould is turned upside down and the wax layer is left to cool and harden.

 

At the base of the mold are set up supply channels (sticks of wax and resin) which are connected to the wax casting cone (future funnel by which we will sink the bronze). Then the inside of the mold is filled with refractory plaster. The casting channels and the cone are covered with this plaster.

 

Retouching

The silicone mold is then opened and the sculpture, which is now in wax with a refractory plaster core, is retouched to rectify the deformations and erase the seal lines of the mold. Other channels are placed around the sculpture and connected to the channels already in place. They will allow the molten bronze to propagate in all parts of this mold in refractory plaster. A second network is created, which is not connected to the casting cone, to allow the gases to escape during the casting of the bronze. Nails, planted through the sculpture, will hold the core in place inside the mold when the wax has melted.

  

The refractory plaster mold

A second mold is created around the wax sculpture. Several layers of refractory plaster are sprayed first to take a very precise impression of the wax. Then it is coated with the same plaster whose thickness varies according to the size of the sculpture.

 

Steaming

The mold is placed in an oven for 48 hours. The temperature is raised up to 300 ° to evacuate the wax that flows through the different channels (dewaxing). Then the oven temperature is raised to 600 ° C to bake the mold and the core, which will have to withstand the casting of molten bronze.

 

Casting

The refractory mold is buried in a sandbox at the height of the casting cone and then filled with bronze heated to about 1200 ° (depending on the composition of the alloy).

 

The release

When the bronze is cooled, the mold is hammered releasing the rough casting and the core is extracted from the inside of the sculpture. This mold has been used only once, unlike the first silicone mold which is carefully preserved for subsequent copies. The channels, now in bronze, are cut off and the sculpture cleaned with water jet and sandblasted.

 

 

Chasing

Here comes the meticulous work of carving that will correct the imperfections, remove the surplus, plug the holes and weld together the different parts of the sculptures if necessary, and finally polish. The bronze then appears yellow-gold. The name of the sculptor (if not already engraved), the edition number, the stamp of the foundry and the year of creation of the bronze are stamped at the base of the sculpture.

 

Patina

The bronze containing mainly copper, the humidity of the air will eventually oxidize it, giving it a green color if the bronze surface is not treated before its exit of foundry. The sculpture is therefore hot oxidized using various acids applied with a brush, which will react the bronze giving it different shades depending on the oxidant and the temperature used. When the desired color is obtained, the oxidation is stopped with a protective coating. For this we apply a thin layer of wax on the sculpture.

 

Finally, after being waxed and polished, the sculpture will reveal all its reliefs, ready to seduce you!

 

 

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