The process for making molds and casts from silicone rubber is quite simple and straightforward. The material is easy to use and delivers excellent results when made in the appropriate manner.
Silicone rubber is a good material that is easy to use when it comes to making molds and casts. Indeed, this material works well for both mold making and casting purposes. It captures excellent detail, cures quickly and turns out to be quite flexible as well. However, it is advisable not to cast the rubber in a silicone mold as silicone rubber sticks only to itself!
How to use?
Silicone rubber comes in two parts and they have to be mixed together in the specified ratio by weight. The rubber itself is of two types – tin-based and platinum-based. The catalysts differ here and they should be chosen based on the purpose.
Keep the pot time and cure time in mind when working with silicone rubber. The mixture will have to be degassed in a vacuum chamber prior to use. This will eliminate the chances of air bubbles spoiling the mold or cast later on.
When it comes to making a silicone mold, the usual technique is to place the model in a mold box before pouring the rubber in a thin stream from a corner of the box. A release agent is not essential as the rubber will not stick to anything.
The material should cover all the sides and top of the model in a thickness of about two inches to ensure that the mold turns out clear and usable. It is always better to keep the mold in the vacuum chamber till it has cured properly. Making a shell mold is advisable.
Once cured, the mold has to be carefully cut all around to extract the model. It will come out easily without getting damaged or distorted in any manner. The mold can be finished before using for making a cast. It is reusable for a number of castings and will last for a long time as long as it is cleaned and stored properly after every use.
The process for making a silicone cast is quite similar. There is no need for a release agent per se. The rubber is mixed and degassed before pouring into the mold and placing in the vacuum chamber. After curing, the chamber is switched off and the finished cast can be demolded easily.
Keep in mind that regular paints cannot be used on a silicone cast as they will tend to chip or crack very soon. Special silicone paint is available in different colors which can be brushed or sprayed onto the cast. This will create a chemical bond with the silicone surface, thus blending in seamlessly to deliver a smooth finish.
When it comes to sourcing silicone rubber and other materials/supplies, EnvironMolds turns out to be a one-stop shop that stocks everything to do with mold making, casting and life casting.