What's the deal with champagne bubbles?

The champagne bubbles are caused by the heat produced when the resin hardens. It produces a lot of heat and blows the bubbles up into a cloudy miasma. Some bubbles collapse together and form large-ish bubbles. You can be really careful mixing resin to not whisk any air into it and still have champagne bubbles in the final cast, and casting thick pieces in water-clear resin is especially bad because of it. This is why people use pressure pot, I think? From what I can gather on the dollshe casting service's equipment explanation, they seem to just ignore it when mixing resin (using an electric mixer) and then vacuuming the resin during casting. Vacuuming resin gets rid of bubbles a lot slower than pressuring, and I see people having to turn on the vacuum several times and turning it off, to make the bubbles escape through the air hole and collapse the resin back. So vacuuming probably requires a resin with a longer pot life than if you use pressure pot. It sounds like you'd also need a stronger vacuum pump if you plan to vacuum resin than you'd need if you planned to just vacuum silicone.

Kind of new to the whole thing...not sure if I have the right of it. But this is what I understand from reading around.

 

Oops I was unclear. Pressurizing silicone doesn't work since it's soft. When you return silicone to normal atmospheric pressure the compressed bubbles would sort of blow up again and deform the silicone eventually. What people do is degas *both* the silicone and the resin, provided the resin has a long enough pot life.