One of the primary problems facing many small scale mould makers is air bubbles in their silicone mould. The bubbles inside of the silicone rubber mould itself are generally not just a serious problem. The problem is as soon as the air bubbles form in the casting surface making the mould unusable.
There are several ways to use to make sure bubble free silicone moulds:
1) Special pouring techniques
2) Applying compressed air
3) Using Vacuum to get rid of bubbles
4) Using pressure to force air into solution
The surface where casting materials meet silicone moulds is the most important part. It is actually therefore essential that additional care is given to make certain no bubbles form when pouring the silicone rubber into the mould box and to the model. It is important never to simply pour the rubber over the top of the the model all at once. Begin with pouring a tiny amount of rubber to the mould box and begin tilting it in several angles to help make the rubber slide over all surfaces. This wets the surface of the model having a fine film of rubber as well as any air bubbles can be easily seen and popped with a pin or paint brush.
Also you can use a paint brush to make use of this first fine film of rubber for the surface of the model. Select the method which works for your fondant cake decoration.
Once you are satisfied that most the bubbles have already been popped you can pour the rest of the mould making rubber to the mould box. Pour from as high a point as you can in a fine stream so that any bubbles within the mixture will pop about the way down. Aim this stream into the corner of the mould box and not on the top of the model.
For those who have access to an air compressor you own an effective way of popping air bubbles. Make sure that you have about 30psi pressure and a small nozzle tip and after pouring the very first tiny amount of rubber into the mould box blow the content within the model to wet the surface in a similar strategy to the initial method. The first film of rubber must be bubble free.
Bubbles are usually a direct result air beaten into the rubber during the mixing process. Ensure that you stir the mix in a steady and slow action. There will still be air in the mixture however and this can be removed using a vacuum chamber.
These vacuum chambers use a vacuum to suck out any air bubbles inside the mixture and convey these to the outer lining where they could be easily removed. Each vacuum chamber has their very own 41dexfpky on how to make use of it but this is tips:
1) Utilize an oversized container for mixing. Allow for the mixture to double in size when put into the chamber.
2) Mix both part A and part B in the container and set in to the chamber. Close the chamber and start the vacuum pump.
3) The mix will start rising to the top of your container. All the air bubbles inside the mixture will rise to the surface. Because the mixture approaches the top of the the container release the valve which breaks the vacuum and the mixture will drop on the bottom along with the air bubbles will pop. Do that 2-3 times to ensure all bubbles are removed.
4) Release the vacuum one final some time and go ahead and take mixture from the chamber. It is now ready for pouring.
Using a vacuum chamber is usually only entirely possible that cake rolling pin which require a fair length of time to put. Several of the quicker setting silicone rubbers sets too rapidly and you also won’t hold the time for you to vacuum the bubbles out. Be sure you examine the label around the product you happen to be using.