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| the bronzing process |
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The artist creates an original piece from clay.
A mold is made of latex, vinyl or silicone supported by plaster which usually destroys the artist's original work.
Molten wax is poured into the mold and swished around until evenly covering the inner surface. This is repeated until desired thickness is reached. When cooled, the hollow wax copy of the artwork is removed from the mold. Molds are used to make more wax copies, but wear on the mold limits their number.
Each hollow wax copy is then "chased" with a heated metal tool rubbing out seamlines where the pieces of the mold came together and "dressing" up imperfections. The wax mw matches the original work of the artist.
The wax copy is "sprued" providing paths for molten bronze to flow.
The "sprued" wax copy is dipped into a slurry of liquid silica, then into a sand-like stucco or dry silica creating a ceramic shell. The shell is allowed to dry and the process is repeated until at least a half-inch coating covers he entire piece. The inside of the cup is not coated, and the cup's flat top serves as the base upon which the piece stands during this process.
The ceramic shell is placed cup-down in a kiln, whose heat hardens the coatings, the wax melts and runs out. All that remains of the original artist's is negative space.
The ceramic shell is cooled, then tested to see if water will flow through the feeder and vent tubes as necessary. Cracks and leaks are patched with thick paste. Thickness can be tested, holes can be drilled and then patched.
The shell is hammered or sand-blasted away, releasing the rough bronze. The spruing which is created in metal is cut off to be used in another casting.
Just as wax copies were chased, the bronze copies are worked until all signs of casting are removed, and the sculptures again look like the original artwork. Pits left by bubbles in the molten bronze are filled and stubs of spruing filed and polished.
The bronze is colored (patina; often green, black,white or brownish) to the artist's preference, using chemicals applied to heated or cooled metal. A sealer (often wax) is applied to protect the piece from ultraviolet rays and can slow the discoloration of patinas by oxidation. |
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