Making of ‘Class Act’ in Changchun, China 2011

Changchun China’s World Sculpture Park

In Aug-Sep 2011 I sculpted a monument size bronze of the ‘Class Act’ and installed it in Changchun China’s World Sculpture Park. The following sections illustrate and explain the various phases of the making of ‘Class Act’.

Armature

In the process of sculpting, an armature is a framework or skeleton around which the sculpture is built. This framework provides structure and stability, especially when a material such as clay is being used as the medium. An armature holds the sculpture erect.

Clay

I created an original model using water or oil based clay.

Mould

A mold is made of the original clay sculpture. It is best described as a shell around the sculpture to register every detail in the negative form. The rigid outer molds contain the softer inner mold, which is the exact negative of the original model. Inner molds are usually made of latex, polyurethane rubber or silicone, which is supported by the outer mold.

Wax

Once the mold is finished, molten wax is poured into it and swished around until an even coating, usually about 1⁄8 inch or 3 mm thick, covers the inner surface of the mold. The wax flows into all the creases and folds, registering all the complexities and details of the sculpture. Ultimately the wax cools down and sets as a positive replica of the original sculpture.

Preparing the Wax for Casting

Removal of wax: This hollow wax copy of the original model is removed from the mold. The mold is ready to make multiple copies, limited only by the durability of the mold.

Chasing wax: Each hollow wax copy is then chased-meaning smoothened and cleaned.

Spruing: The wax copy is sprued with a treelike wax arms that will eventually provide paths for molten casting material to flow and air to escape.

Slurry: A sprued wax copy is dipped into slurry of silica, then into 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. It is called ceramic shell because this slurry is dried and baked.

Burnout: The ceramic shell-coated piece is placed cup-down 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.

Cast

Pouring: The shell is reheated in the kiln to harden the patches and remove all traces of moisture. It is then placed cup-upwards into a tub filled with sand. Metal is melted in a crucible in a furnace, and 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.

Release: The shell is hammered or sand-blasted away, releasing the rough casting. The sprues, which are also faithfully recreated in metal, are cut off, to be reused in another casting.

Finish

Just as the wax copies were chased, the casting is worked until the telltale signs of the casting process are removed, and the casting now looks like the original model. If the sculpture is cast in parts, then at this stage the parts are welded together to form the final rough sculpture. Pits left by air bubbles in the casting, seams from welding, and the stubs of spruing are filed down and polished. At this point it is dressed with patina, a hot or cold chemical reaction that colors the metal surface permanently. And finally, the sculpture is sealed to secure and protect against weathering.

Install

Installing a monument size sculpture requires a lot of site preparation, team work and heavy machinery. This 7 ½ feet ( 2 ½ meter) sculpture was permanently installed in the park on the 1^st of Sept 2011.

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