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AT THE FOUNDRY
1. PLASTER
Once completed in the studio, the plaster work is sent to a foundry to be cast in bronze.
Michel BASSOMPIERRE's bronzes are always cast in 12 copies (8 + 4 artist's proofs). They are therefore original works of art. Beyond 12 copies, they are referred to as "multiples ."
2. CREATION OF THE MOLD
Several layers of liquid elastomer (a highly elastic material) are applied to the work with a brush to facilitate demolding. This flexible impression is held in place by a plaster cap reinforced with sisal (a plant fiber used in the manufacture of ropes).
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3. MAKING THE WAX MODEL
The inner wall of the mold is covered with melted wax, in layers, until the desired thickness is achieved. This thickness of 3 to 4 mm will correspond to the thickness of the bronze after casting. Once the wax has cooled, it is removed from the mold and reworked to correct any defects.
4. INSTALLATION OF THE FEEDING SYSTEM AND CASTING OF THE BRONZE
Wax coils are glued together to create a highly complex network of “pipes” that allow air and gases to escape and the bronze to be cast. The wax model and its network of pipes are covered with refractory plaster. A metal cylinder encloses and secures this assembly. Only one opening (called a pouring funnel) is visible at the top of the mold, designed for pouring in the liquid bronze.
5. DEMOLDING
This operation, carried out using a high-pressure water cleaner, consists of breaking the plaster mold to reveal the “cast bronze.”
The mold is then heated to 700°C to remove the wax and any traces of moisture.
The molten bronze (at 1140°C) is poured into it.
Bronze is an alloy composed of tin and copper that art foundrymen keep in ingot form. Its composition varies, but generally includes between 70 and
85% copper and 15% tin.
6. DEBURRING
This raw cast bronze is an exact replica of the wax. The network of pipes, which was made of wax before casting, is now made of bronze. Using grinding wheels and disc grinders, the chiselers cut and remove all the pipes.
7. CHISELING
The chiseler polishes the bronze using increasingly fine abrasives to bring out every characteristic detail of the original model. Michel Bassompierre's rounded works are part of what is known as “smooth polishing.” This highly demanding technique is mastered only by the best workers in the foundry.
8. BRONZE PATINA
The work can finally receive its final color, called patina. It is the result of two simultaneous actions: the application of different mixtures of metal oxides and acids to the surface of the work with a brush, and the passage of a heat source with a torch.
Depending on the desired color, a specific mixture will be applied. Without this, a chiseled, golden bronze will naturally oxidize and turn green.
Finally, a thin layer of beeswax is applied to polish and shine the patina. The bronze is now ready to stand the test of time.
