Part of the process
Molds and release
Silicone molds release epoxy without help, and the mold surface decides the finish: glossy mold, glossy piece. Rigid molds and wood forms need a release agent or tape.
- Silicone molds
- no release agent needed
- Rigid plastic or wood forms
- release agent or sheathing tape
Most hobby casting is done in silicone molds, because epoxy does not bond to silicone. The piece copies the mold surface exactly: a glossy mold gives a glossy cast, a matte or scratched mold gives a dull one. That is why molds are cleaned gently and kept free of dust. How to clean resin molds covers care and storage.
Silicone needs no release agent, though a light mist of mold release is optional. Rigid plastic molds, wood forms and anything porous are different: epoxy grips them, so they get a release agent or a lining of sheathing tape. Mold release substitutes covers what works when there is no spray in the house, and the mold release spray guide compares the real thing.
You can also make the mold yourself from two-part silicone poured over an object in a small box. Common mold-making silicones mix 1 to 1 by volume and cure in 4 to 6 hours. How to make silicone molds for resin walks through the box, the pour and the amount of silicone to buy.
Common mistakes at this stage
- Scraping cured resin out with a metal tool and scratching the mold.
- Pouring into a rigid mold with no release agent.
- Expecting a glossy piece from a matte mold.