Once the silicone is mixed, it must be degassed. The yellow bell jar connected to the blue vacuum tank is what we use for degassing. You put your mixed silicone in the jar and crank up the vacuum. It's pretty fun to watch the air (bubbles) being pulled out of the mixed rubber. Once the rubber is mixed, it's time to pour.
We are located in NY, and it's July- so it is really hot and humid. We're not doing this in a temperature controlled environment as we should be. Water (humidity) getting into the silicone can cause it to not cure, and heat can cause the silicone to kick (cure) faster than is optimal, trapping bubbles.
The pressure tank to the right is what the mold is placed in to further draw bubbles out of the casting.