How to Make Rubber Molds for Fake Rock
Fake rocks can be used to landscape, to cover items outdoors such as speakers or in the house for decoration. Industrial-made fake rocks can be very expensive, but you can make fake rocks at home using a molding process designed for casting plaster ceiling molding. A model of the desired rock will need to be constructed prior to casting the rubber mold. The model can be made from spray Styrofoam insulation and then carved into the appropriate design.
- Difficulty:
- Moderate
Instructions
Things You'll Need
- Silicone
- Catalyst
- Measuring cups
- Mixing container
- Wax-coated box
- Stir stick
- Rock template
- Petroleum jelly
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Block Mold Instructions
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1
Locate a wax-coated cardboard box a minimum of 2 inches larger than the fake rock model. Apply a layer of petroleum jelly to the inside of the cardboard box.
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2
Mix the silicone and appropriate catalyst together in a mixing container. Stir the mixture until no striations are visible. Scrape the bottom and sides of the mixing container periodically to ensure an even mix. Let set for several minutes prior to use to allow any air bubbles to escape.
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3
Place the model of the fake rock into the greased box. Slowly pour the silicone mixture in to one corner of the box to prevent air from being trapped in the mold. Continue pouring until the fake rock is covered by a minimum of 2 inches. Allow to dry according the directions on the silicone and catalyst mixture.
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4
Carefully lift the mold out of the box. If necessary, cut the box if the mold does not want to release, but be careful not to cut into the mold.
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5
Remove the fake rock model from the silicone. The mold is now ready for use.
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1
Tips & Warnings
A hardwood box can be made to hold the fake rock model. An acrylic spray lacquer should be sprayed on the inside of the box to close all pores.
Complete the process in a well-ventilated area. Do not breath the fumes directly when mixing the silicone and catalyst.
