TLDR: Both are devices to help remove air bubbles from your project: a Vacuum chamber pulls the air out of your material using a vacuum and a pressure pot shrinks the bubbles in your material using pressure.
Vacuum Chambers vs Pressure Pots
- What are they?
- How do they work?
- When do you use them?
Let’s keep it simple…
Vacuum Chamber = Air Out
Pressure Pot = Air in
Essentially, the vacuum chamber takes your material and pulls the air out of it by pulling an actual vacuum within the metal container and a pressure pot, using an air compressor with an inlet attached, actually puts a ton of air into the metal pot, pressing against the mold and material and shrinking the air.
Vacuum Chamber Overview
The vacuum chamber uses a pump to force air out of the chamber and, subsequently, out of the material. If you’ve mixed up a bunch of silicone and have introduced a lot of air, the vacuum chamber kicks into high gear, pulling all the extra air out of your material through a hose. It naturally pulls all of the small bubbles that are within your silicone, to surface and pop and release.
Q: So, would you use resin in a vacuum chamber?
A: Well you can, but there are a couple of factors where you normally wouldn’t. Resins have a shorter open time and cure quickly, limiting their use with vacuums. By the time it takes to get all of the air off, your resin is going to be firing off, it’s going to get hard, and you’re not going to be able to use it. (Not super helpful when using resins most of the time.) You can still get a lot of air out of the resin, but you’re going to pour it again, meaning you’ll just introduce more air to it.
Silicones, however, naturally evacuate air so they’re a great fit for vacuums! A vacuum chamber can typically release 99% of the air – pouring it into the mold then allows the other 1% to release, making for bubble-free molds!
Pressure Pot Overview
This adds air, compresses everything that’s in there, and shrinks the air until it’s impossible to see with the human eye.
Q: Why do we do that?
A: Well we, want to do that for rigid resins, things that have a short open time where you want that clear, glass-like finish part but you don’t have time to get all the air out through something that’s going to take a while (like a vacuum chamber). You just need to, real quick, hammer it to nothing.
All the compressed air and intense pressure shrinks those air bubbles, the rigid resin fires off, and the material is stuck like that – the bubbles are never coming back! If you put silicone in a pressure pot, well, that rubber’s going to shrink and that air is going to go away but the minute you open it up, and the atmospheric pressure comes back to normal, those air bubbles might come back (because that rubber is flexible).
Related Article: How to Use a Vacuum Chamber
Related Article: How to Use a Pressure Pot
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