Do I have to vacuum de gas the silicone rubber? Is vacuuming the rubber that important?
Silicone rubbers are thick and most have a high viscosity. Silicones do not de-air themselves as readily as urethane rubbers and need to be vacuumed to remove entrapped air.
Consequently, if you mix and pour silicone rubber that has not been vacuumed, air may be trapped in the mixture as it turns from liquid to solid and these bubbles may show up on the working surface of the mold.
Remedy: If you are going to be making silicone molds on a regular basis, invest in a vacuum pump and vacuum chamber – approximate costs: $800 - $1,000. (You can also choose to use a urethane rubber instead of silicone rubber. Be prepared to use a sealing agent and release agent to prepare your model as directed.
The FAQ list is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Material Safety Data Sheets (MSDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.