Mold making and Casting products through EnvironMolds, LLC

Silicone rubber is a material of choice for making molds of figurines, giftware and robotic figures to even prototype tooling, prosthetic pieces and special effects. A wide variety of silicone rubbers are available in the market ranging from the regular silicone formulations to skin safe, food safe and skin-like translucent options.



Not only does silicone perfectly capture the surface details of a model, but the rubber is very simple to use too. Following is a look at what goes into making a simple silicone mold:

•    Silicone rubber is a two-component material with the base and catalyst usually mixed in the ratio of 10:1 by weight. You need to stir and shake them properly before weighing the appropriate amounts in separate containers. Place the base material in the mixing container and roll it around to coat the sides as well.


•    Pour the catalyst into the container and mix them thoroughly making sure that any material is not left unblended on the sides or bottom. You should not use a mixer machine or even mix too vigorously as this will introduce air bubbles into the silicone rubber.

•    Despite the most careful mixing, some air is bound to get entrapped in the mix and will form unsightly bubbles on the mold. Degassing in a vacuum chamber will release the air and make the rubber bubble-free.

•    Once vacuumed, slowly pour the mixture in a thin stream from a corner of the mold box till a thick and even layer forms all over the model.





•    Keep in mind that though the work life of silicone varies from one brand to another, it is usually under an hour. Even the pot life is limited to a couple of hours at best.

•    As silicone rubber does not stick to anything but itself, it will get demolded easily. Yet, some mold makers prefer to coat a thin layer of release agent to allow the mold to slide off without any effort. Sealing the model and mold box is essential as the rubber may get absorbed into them.

•    The rubber mold requires 16 to 24 hours to air cure. Demold only when the mold feels rigid and is no longer tacky. Allow it to remain at least another day before proceeding to casting. Full cure may take almost a week.

•    The cured silicone rubber mold is usually blue in color. It will reproduce the exact detail, have a smooth finish and is ready for casting. You can cast polyurethane resin, epoxy resin, polyester resin, polyurethane rubber and many other materials in the silicone mold simply by pouring the material into the mold. Demolding the cast is also easy as silicone rubber will not stick to anything.



In sum, silicone rubbers are a great option for making molds of various objects.