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How is plaster used to make molds and casts for sculpture?
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Sculpture
Visitors viewing A Subtlety, or the Marvelous Sugar Baby, a sugar-coated polystyrene sculpture by Kara Walker, 2014, part of a temporary installation at the former Domino Sugar Refinery in Brooklyn, New York.
In sculpture, plaster is a versatile material used both as a medium for direct modeling and as a primary material for creating molds and casts. Because it does not significantly shrink or crack when drying, it is an excellent medium for reproduction.12
Plaster Molds
Plaster is used to create two main types of molds:
- Waste Molds: Liquid plaster is built up over an original model (typically clay). Once the plaster sets, the mold is removed, cleaned, and filled with a casting material like concrete, resin, or more plaster. Finally, the mold is chipped away from the finished cast, destroying the mold in the process.1
- Piece Molds: These are constructed in sections that can be removed from the original model without damaging it. These sections are keyed together and supported by a plaster case. Because they are reusable, piece molds are ideal for reproducing existing sculptures or for slip casting in pottery.1
Direct Use
Sculptors may also work directly in plaster of paris, applying it over an armature and shaping it with spatulas, rasps, and chisels to achieve an immediate, finished form.23