The Lost Wax Process





ORIGINAL ART

The most intricate works can be faithfully reproduced via the lost wax process. The original artwork can be composed of many different materials depending on the sculptor’s preference, although oil based clay is the most commonly used medium.

 

MOLDING PROCESS

A mold is made of the original model or sculpture. Molds are composed of two layers, a rigid outer mold containing a softer inner mold which is the exact negative of the original model. The molds produced at Legacy Art are made of high quality silicone and a plaster or fiberglass outer mold. The finest details and texture will be captured by this type of molding process.





WAX CHASING

Once the mold is completed, it is used to create an exact wax reproduction of the original artwork. Wax is poured into the mold and swished around until an even coating, usually about 1/8” -1/4” thick, covers the inner surface of the mold. Once it has cooled, a hollow wax reproduction of the original model is pulled from the mold. The wax is then chased with hot metal tools and dressed to cover any imperfection. Finally the wax copy is sprued with a treelike structure of wax that will eventually provide paths for molten metal to flow and air to escape.



CERAMIC SHELL

A sprued wax copy is dipped into a slurry of silica, then into a sand-like stucco, or dry crystalline silica of a controlled grain size. The slurry and grit combination is called ceramic shell mold material, although it is not literally made of ceramic. This shell is allowed to dry, and the process is repeated until at least a half-inch coating covers the entire piece. The bigger the piece, the thicker the shell needs to be.



METAL POURING

The ceramic shell-coated piece is placed in a kiln, whose heat hardens the silica coatings into a shell, and the wax melts and runs out. Now all that remains of the original artwork is the negative space, formerly occupied by the wax, inside the hardened ceramic shell. The feeder and vent tubes and cup are also hollow. The shell is reheated in the kiln to harden the patches and remove all traces of moisture, then placed cup-upwards into a tub filled with sand. Metal is melted in a crucible in a furnace, then poured carefully into the shell. If the shell were not hot, the temperature difference would shatter it. The filled shells are allowed to cool. The shell is hammered or sand-blasted away, releasing the rough casting.



METAL CHASING

 Just as the wax copies were chased, the metal casting is also chased to remove the telltale signs of the casting process; this would include grinding, welding, sandblasting and polishing the metal. Once the metal chasing is complete, you are left with an exact reproduction of the original model.

PATINA

At the end of the journey, the artists can decide to finish off their piece with a high polish, such as in stainless steel pieces. In the case of bronze however, the artist will most likely opt for a patina finish. The application of patina, also called “distressing” is a highly skilled process. Various oxidizing chemicals are layered onto the metal to achieve different colors and patterns on the bronze. Our master patineur has over 20 years of experience and is sought after for his ability to interpret the vision of any artist from traditional to non-standard patinas.

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