A mother mold is a brushable/trowelable plastic shell that is applied to the outside of a flexible rubber mold. The rubber mold can be made of silicone, urethane or latex.

The purpose of the mother mold is to provide a hard backing for the soft flexible mold. This enables you to make a mold with a thinner wall thickness, which can save money and material.

The most common application is to make the flexible mold out of a brushable silicone, such as our AM 128 with the thixotropic brush additive. You brush the silicone rubber on the master to a thickness of about ½ inch (less if the mold is small) then allow it to dry. When the silicone is dry, mix the mother mold material and apply it with a spatula or stiff brush to the outside of the silicone rubber mold. The working time of the mother mold is about 9 minutes and it will be usable in about 2 hours.