How to Cast Resin Types

Prepare the resin. Polyester is the most common type of resin used, but it must be prepared for use first. Wearing gloves, add a small amount of MEK Peroxide, which can vary from 1 to 2 percent, depending on the temperature of the room. This will help the polymerization, or hardening, process. Also remember that laminating resin cannot be used for casting because it will not fully cure when exposed to air. Make sure you use a casting formula.

Create your mold. When deciding on a size and shape for your mold, remember that all resins shrink as they harden, and because resin adheres quickly to the surface, any irregularities like bumps or ridges might cause problems.

Treat the surface of the mold with a release agent like non-silicone wax. Any molds made of polystyrene will be destroyed by the resin, and some plastics will break down, so polyethylene molds are best. Also, molds with a shiny surface provide a better finish.

Pour the resin. You have about one-half hour from the time you mix your resin until it begins polymerization. Measure the high mark on your mold to get accurate sizing and then pour in a slow, steady motion. If you're pouring a large cast, doing the entire thing at one time my cause damage to the mold because of the shrinkage. After the top layer has gelled, cover with a cellophane sheet to keep out air and let the mixture cure, or harden, completely.