Although a vacuum pump and chamber will make your life easier if you are making silicone molds on a regular basis, it is a lot of money to spend on equipment. Some of our mold makers who do not own vacuum equipment claim that the following method works well to minimize bubbles in their finished mold:
- Mix a small batch of silicone to apply a "detail coat" to the model, using a similar stippling technique for making the first layer of a brush-on mold.
- Optional: Use a can of compressed air to pop any bubbles still remaining on the model surface.
- Mix the remaining silicone required to make the pour mold, then slowly pour off-model into the lowest point of the mold box, allowing the silicone to seek its own level. Pouring in a thin stream from a height of 2-3 feet allows entrapped air bubbles to elongate and break while pouring.