Pressure cooker vacuum chamber

I needed a small vacuum chamber to degass clear casting resin. So I made one.

Note: I would seriously recommend against using acrylic sheet in this application. When it fails, it fails catastrophically, potentially showering the area with very sharp fast fragments. While we're on this subject, you are responsible for anything you do, not me. Following these instructions is not recommended unless you have a good understanding of the forces involved.

For the vacuum source, I use a normal compressor. Any one will do, just as long as you can attach to the suction side (the side that normally has a filter on it). To attach, I just used a 15mm PEX pipe section which I screwed into the fitting, unscrewed then covered in PTFE tape then screwed back in again. I then reduce the 15mm pipe down to 8mm PEX pipe, since it's more flexible. At the other end of the pipe, I again bring it back up to 15mm with a straight pipe adapter. This is easily good down to -27 inches of mercury (0.1 atmospheres).

Bits you'll need

To get the air out, you'll need a hole. I used a 15mm "speedfit" plastic tank connector, for which I drilled a 28mm hole.
You'll also need to apply a strip of neoprene to the top of the pressure cooker - The supplied rubber ring is great at retaining pressure, not so good at holding it out.

Take the tank connector and form a neoprene gasket on the inside. This is simply taking the neoprene strip and running it round the outside of the flange. Note that this one has already been used and compressed, hence the dents. When you've made one complete loop, leave a small overlap.

Place the tank connector in the hole you've just cut, ensure it's centered, and screw on the outer fitting. No need for any rubber or neoprene on the outside - The inner gasket forms the seal.

Connector installed.

Ready to pump down

On the bottom of the sheet of lexan I have attached neoprene feet so you can put it down without worrying about scratching or contaminating the bottom surface.

Now all you need to do is attach a hose to your vacuum source, put the lid on, pump it out and watch the fun :)

A small video of pumping down the chamber with 1/3 of a glass of shaving foam (warning - The compressor is loud):