How to Make a Rubber Mold for Faux Rock
Faux rocks are used in all kinds of projects. You can use them for making models or dioramas, for model railroads or even very large stones for incorporation into landscaping projects. You can hide a speaker inside a faux rock or you can build a fireplace surround that looks like real stone. With so many possibilities it's easy to understand why making rock molds can be a useful solution to adding rocks to your project.
Things You'll Need
- Scrap plywood larger than the rock
- Release agent (optional)
- Rock
- Latex or silicone rubber
- Dozen disposable brushes
- One-inch cheesecloth strips
- Talcum powder
Instructions
-
-
1
Position scrap plywood in a well-ventilated location where it can remain for at least a week.
-
2
Place one or more (clean) rocks on the plywood. The rocks should have a bottom side that is relatively flat as the mold must have an open side in order to remove the stone that is being molded. It is also helpful to have the widest part of the stone be the portion that is at the bottom.
-
-
3
Apply a release agent to the rocks if the type of rubber you are using requires an agent. Different types of rubber molding products have individual requirements to allow the rubber to release from the object being molded.
-
4
Paint the rock with a coat of latex and allow the latex to dry to the touch. The dry time will vary depending on your level of humidity (silicone type rubbers dry faster than latex). Also paint one patch of the plywood with the latex at the same time. You will use this patch to determine the thickness of the rubber on your mold.
-
5
Apply at least eight to 10 coats of latex to both the rocks and the patch.
-
6
Coat both sides of a cheesecloth strip (long enough to fit the area you are working) and position the cheesecloth over the stone. Your objective is to add strength to the rubber mold by covering the shape of the rock with a layer of cheesecloth. Because stones are uneven, you may need many small strips. Once the strips are in place, coat the entire piece again. Add a small piece of cheesecloth to your plywood patch in a similar way.
-
7
Add additional rubber layers if your stones are large in size. You may want a mold as thick as 3/16 of an inch (check your plywood for thickness). Small stone projects, such as those used for models, may need only 10 to 12 layers of rubber.
-
8
Allow the rubber to dry for two to three days before removing the mold from the stone. Apply talc to the inside of the stone before casting.
-
1
Tips & Warnings
Cut along the bottom of the mold to create a level recasting surface. Consider positioning the mold in a bed of sand if you are casting concrete products. This will give the mold additional support.
