Making Plaster Press Molds Using Styrofoam as a Building Block

A Lightweight Sculpt-able Material for Press Mold Prototypes

Plaster Press Molds

Christie Brown carves styrofoam into various shapes, like this torso. Later she will use these shapes to create plaster molds for press molding.

I realized that we were really due for a sculpture post here on CAN, so today I am featuring the work of Christie Brown. This post doesn’t only pertain to sculpture though. Christie’s techniques could easily be adapted for functional work.

In today’s post, an excerpt from Ceramics and the Human Figure, author Edith Garcia explains how Christie makes her molds from styrofoam models and then press molds and assembles her work. – Jennifer Poellot Harnetty, editor.

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Plaster Press Molds

This was excerpted from Ceramics and the Human Figure, which is available in the Ceramic Arts Network Shop!

Plaster Press Molds

She seals the Styrofoam with shellac to protect it from the clay’s moisture.

After she has finalized her clay sections she creates her multi-piece molds by placing shims around the edges of each piece — this allows her to create two-part molds for each section. After the creation of the plaster molds on the clay-covered Styrofoam, she is then able to remove the clay/Styrofoam core and allow the plaster sections to dry.

Within a few days, Brown can roll out clay slabs then pressmold them into the dry plaster sections.

After allowing the clay to become leatherhard, she is able to assemble her pieces.

Plaster Press Molds

Brown covers the Styrofoam core with a fine clay and places it on plinths to raise it slightly above the table.

Plaster Press Molds

The clay-covered leg is sectioned off with the use of metal shims to create an outer edge for the plaster mold.

Plaster Press MoldsBrown builds up the edge of the shims with clay to ensure that the plaster stays on top of the clay piece as it sets.

Plaster Press MoldsThe first part of the plaster mold has set and she is able to remove the metal shims on the legs. She then adds a clay wall to the edge of the plaster mold as well as a releasing agent such as soap.

Plaster Press MoldsBrown allows the mold to dry in the sun and begins the process of press molding clay. After the clay has hardened to a semi-hard state, she joins the two sections using slip.

Plaster Press MoldsThe sculpture is painted with a white vitreous engobe and placed in a kiln in sections and fired to 1000 degrees celsius. Then it is painted with colored englobes, oxides and dribbles of clear glaze, then refired to 1180 degrees celsius

Plaster Press MoldsIn the completion of her works, she fires them to Cone 04 and finishes the surface with the application of watercolor-like underglazes. In this way, she is able to create surfaces that have a subtle yet beautifully-layered, transparent quality.

Click here to see more of Christie Brown’s work.

**First published in 2015.
  • Thanks for that, Lisa. Great interview and it even answered my question below! Amazing work, Christie.

  • Strange, unusual figure, i like it! I can’t believe you didn’t give us an image of the finished piece once again! I’m not sure why that is such a common occurrence here at CAD? I have a few questions about Christie’s process: if these are one-offs, why go to all the trouble of making a styrofoam model, plaster mold, multi-parts, etc, and not use that mold more than once? It seems like with less effort you could just make the one-of-a-kind figure out of clay and be done with it. What is your reasoning there? Nice piece, though!

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