How To Use Silicone Rubber

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.

silicone RTV rubbers

•    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.

Quality Silicone Mold Rubbers

•    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.

mold making silicone rubber

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

Get Going With Mold Making

Mold making is something that may sound bland and boring to a beginner. But once you get down to actually doing it, making a negative image of a model with your own hands can be incredibly exciting.

You can choose anything to begin with – be it a small figurine you especially like, a spare handle or even something ordinary lying around in the house. Indeed, it is possible to make a mold of just about anything that catches your fancy, your own body included!

If you are wondering about how to make a mold, there are varying techniques and you can use diverse products as well. In fact, a simple material like clay is the best mold making material for a novice. All you have to do is shape the malleable clay to form a covering over the model. Once it dries, remove it gently and you can see the silhouette of the model captured on the underside, complete with all the curves, folds, nooks and indentations.

Apart from this, wax, plaster bandages, alginate, moulage, polyurethane resin, latex rubber, silicone rubber and many other materials can be used to make a mold. You will need other products and accessories too - like sealer, release agent, vacuum chamber, mixer, brush, spatula, etc. – depending on your choice of technique and materials. All these can be easily sourced from EnvironMolds.

Again, a mold is not always ready in one go. At times, you may need to make two part molds or even multi-part molds for more complex shaped models.

All this may sound pretty complicated, but slowly you will find yourself able to make keys, spues and more very easily. And the satisfaction of using your mold to create a spitting replica in the form of a cast is simply incomparable!

EnvironMolds, LLC
18 Bank Street, Suite 1,
Summit, NJ 07901, USA
Call: (866) 278-6653
Fax: (908) 273-9256