How to tell when RTV is done degassing

Hi everyone! I'm kind of new here so go easy on me. I recently built myself a vacuum tank (or rather a vacuum lid to put on my pressure tank) so I could degas RTV (Smooth-On's Mold Max 30 in this instance) for larger molds. When I put the mixed RTV in the tank and hit the vacuum (29"hg WOOO) it expands all huge-like and bubbles away, then settles down and starts to boil. My question is do I leave it to boil? or once it starts boiling is it done? And if it's not done how long should I let it boil for? Sorry if this seems like a silly question but I couldn't really find an answer for it in the other vacuum chamber threads.

Here's a shot of my tank and the Mold Max in a bucket. It's a little messy but it works well. (.5 plexi for the lid with an input, release, and vac gauge, routed .375" and filled with Mold Max 30 for the seal.)

Once it rises and then falls back down a vast majority of it is degassed and most people will call it a day and pour shortly after this point, but as you can see it's still boiling small amounts of gas off so letting it go longer is only helping remove more gas... You have to factor in your mixing time as well a pour time but leaving it boil for several minutes (5 or 10 depending on your work time) after it falls never hurts and is only making it better, just don't boil so long that you close your working window... A few minutes too long can really make for a bad day, know your product and know you work time, and adjust for the ambient temperature... Hotter = less work time...

Ahh okay awesome! Thank you for the quick and informative reply!

I pull it out of the chamber the second after it falls. I've never seen a bubble in a mold I've made, by the way.

That actually does make me feel better about pulling out the RTV sooner, thank you

If I'm using a silicone with a pot life of say 30+ minutes I let it degass for another 2 minutes after it falls. Any thing less then 30 minutes and I stop right after it drops.


Sent from somewhere in space & time...