Mold making pointers 2.0

Casting Strategies: An intensive course in safe and efficient methods of rubber mold making.

Introduction: The ability to make molds is one of the most valuable and useful skills an artist can possess. Molds allow for the production of multiples and the knowledge of how to make proper molds will open up a wide range of material possibilities for artists.

Flexible molds enable the casting of complex positives and, when made properly, can yield many more cast editions than a plaster mold. There are many different types of rubber compounds that allow you to cast a variety of materials within them – from plaster to wax to rubber itself. A good resource for detailed information on types of rubber and their applications can be found at the Compleat Sculptor (90 Van Dam St. NY) and on the Polytek or Smooth-On websites.

Mold making is a time-intensive endeavor. Here are some basic guidelines to follow when making flexible molds:


¸ Have patience and time. Successful molds take time (usually more time than you think, so plan ahead!) There is no point in spending the time to make a mold that fails because you rushed it.

¸ Use the flexible material that is appropriate for your application. Rubber compounds come in different grades of hardness. There are pourable types and brushable types. There are kinds that can withstand higher temperature casting materials and / or react differently to certain casting compounds.

¸ Read and follow the MSDS. ALL materials come with a Material Safety Data Sheet. These can always be found easily online. The MSDS gives you important information about the safe handling and possible hazards of working with a material. Always wear gloves when working with rubber compounds and any other appropriate safety apparatus directed by the MSDS

¸ Seal your positive when necessary. This is usually something like shellac or polyurethane, but you should always check the material handling specifications that come with your mold materials and know what works best with the material of your positive.

¸ Use Klean Klay or another sulphur-free dam material when using most rubber compounds to make a mold. Water based clay will inhibit curing of some rubbers.

¸ Use the specified release agent for your type of rubber. Never use Vaseline or grease as you would for plaster or other materials.

¸ Be sure to have a plan for keying and making mother-molds. Mother molds consist usually of plaster and create a shell to help your rubber mold from distorting. They also save money by allowing you to make thinner walled rubber molds. You must eliminate all drastic undercuts with the rubber mold before applying a mother-mold.