Positive Original negative mold positive wax negative shell positive bronze
Art Casting of Illinois, Inc.

Art Casting of Illinois, Inc.
Adagio Fine Art
Dr. Harry & Karly Spell Foundation
The Michelangelo Project
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Rubber Molds

Art Casting of Illinois, Inc. uses rubber molds as part of our process. It is the first step after the original has been brought to us. Depending on the size, original material, and budget, and final product, various types of rubbers are available. A painted on polyurethane rubber is the most common because it is long-lasting, captures very fine detail, and is the least expensive. A plaster mother matrix helps to reinforce the rubber. This mold will last 10 years if kept in a cool dry environment or an edition of up to 40 waxes or plasters have been pulled from it. Another option is silicon rubber, which can be used in making wax copies used for bronze casting, as well as copies made from a variety of other finished materials. Our molds are very well engineered and created to receive the most use possible from them. Each mold takes approximately 2 weeks to complete, depending on the size, the time may vary.

Taking apart a finished polyurethane
rubber mold

This image is of the final step in the mold making process. The white is the reinforced casting grade plaster mother matrix over the rubber. The original is underneath, which happens to be Sheilah McGee's Buffalo.

Each plaster mother matrix is made in several pieces so the undercuts will not catch and the wax will not break.

Depending on the complexity of the piece, the number of pieces involved will vary. This piece has many small features and required a more complex mold.

The rubber squares are called keys, they lock in place with the plaster mother matrix and help retain the shape of the original when making the wax or plaster. Without these keys, the mold will distort and the piece will look deformed.

After all the plaster is removed the rubber is cut away carefully paying attention to undercuts which allows the wax or plaster to be easily removed without breaking.

©2009 Art Casting of Illinois, Inc. Lydia Koepke
Last Updated July 19, 2010