Introduction: Pressure Cooker Vacuum Chamber

Picture of Pressure Cooker Vacuum Chamber

Pressure cookers make great vacuum chambers because they're readily available, not too expensive, and are strong enough to hold a full vacuum. Once you've found all of the parts, assembly is straightforward and can be a fun afternoon project.

For this build, I wanted something robust enough to withstand many uses, and reliable enough to work every time. It also needed to be as big as possible, because why not? If your needs are more modest you can use a smaller pressure cooker (they come in many sizes) and maybe use a thinner sheet of acrylic (or switch to a polycarbonate). Although, I'd caution you to do a stress analysis before using anything thinner. Acrylic fails catastrophically, and it's hard to try again while picking plastic out of your eyes. Better safe than sorry. And remember, always wear proper eye protection!

Step 1: Assemble Your Materials

Picture of Assemble Your Materials

You'll need to find, make, or buy the following items

  • 22-qt pressure cooker
  • 16"x16"x1" sheet of acrylic
  • Vacuum pump
  • Several feet of 1/4" copper tubing (the hardware store variety is fine)
  • Copper tube cutter
  • 3/4" drill bit
  • MPT vacuum gauge
  • FPT bulkhead fitting
  • FPT cross fitting
  • NPT T-fitting
  • 3x FPT ball valves
  • 3x NPT to compression adapters
  • 3x MPT couplers
  • Compression to Flare adapter
  • 3/4" ID rubber gaskets (at least 1/8" thick)
  • Teflon tape

I used a Miro 22-quart aluminum pressure cooker, and a Robinair 15300 vacuum pump. Both were available from Amazon and reasonably priced, but there are plenty of other sources for each. That particular pump comes with 3/8" and 1/4" Flare fittings on the inlet port, which is why I needed a compression-to-flare adapter. If your pump has different fittings, you'll need to use the appropriate adapter.

For the 3/4" drill bit, I used a low-end black oxide bit from the local hardware store. This isn't the best choice for this application, but it's all they had, and I only needed it to work once.

All of the fittings are standard 1/4" NPT brass fittings. I found them at a local supply store, but they're generally available online for about the same prices. I used a cross-fitting as the central fitting in this setup so I would have an extra port for future use. You can just as easily replace the cross with another T-fitting, and use one less ball valve, to save a little money. Fewer fittings means less leakage, and better vacuums, so feel free to remove anything you don't need.

Step 2: Assemble the Fittings

Picture of Assemble the Fittings

Let's get the easy part out of the way first. For this step, you'll need your bag of fittings, the valves, the pressure gauge, a roll of teflon tape, and a crescent wrench.

Assembling brass fittings is pretty easy, but you do have to be careful. Brass is a very soft metal and you can easily strip the threads if you over tighten the fittings. But, at the same time, if you don't tighten them enough, the whole thing will leak. The teflon tape helps seal up the threads with less tightening, but it's not magic. Don't worry about this too much right now. Just get everything assembled in the right order and we can worry about any leaks later.

The fittings go together in the arrangement shown in the picture above. Just assemble the fittings one at a time, in whatever order works for you (but start with the pressure gauge, see below). Ignore the bullhead fitting, and its associated compression fitting, for now. We'll worry about those in a later step.

Make sure you wrap each male thread in at least one layer of teflon before installing. If this is your first time using teflon tape, it can be tricky, and it feels like you need 3 or 4 hands to do it, but you'll get the hang of it. I've found that it works best if I wrap the tape opposite the direction that the fitting will turn while you're tightening it. This helps keep the tape from bunching up inside the female side of the connection. So, if the fittings are "righty-tighty" (aren't they always?), then wrap the tape the other way.

Once you're finished you should have something like the last picture above. I ended up with the pressure gauge on the wrong side because the T-fitting finished tightening upside down, so I just flipped the cross over and swapped the adapter fittings. You should probably start the assembly with the T-fitting and pressure gauge so that you don't get stuck swapping fittings around just to get the gauge right side up.

Step 3: Prepare the Pressure Cooker

Picture of Prepare the Pressure Cooker

Now for the fun part. In this step, you'll be drilling a hole in your nice shiny new pressure cooker. I know, it's tough, but it's for a good cause.

You're going to need:

  • A metalworking drill press
  • The pressure cooker
  • A 3/4" drill bit
  • Several smaller drill bits
  • Various clamps and bits of wood
  • A deburring tool

Because all of my other fittings are 1/4" NPT, I chose to use a 1/4" NPT bulkhead fitting for the vacuum port into the pressure cooker. Of course, the fitting itself is much larger than 1/4", so we'll need to drill a bigger hole, namely a 3/4" hole. To do this you'll need a drill press big enough to handle your pressure cooker. You might be able to use a hand drill, but with a 3/4" bit, I wouldn't recommend it.

Start by removing the lid from your pressure cooker (mine came with the lid attached), and notice that there's a rubber gasket inside the lid. Don't damage the gasket; we'll be using it later. We won't be using the lid, but it's protecting the gasket, so for now just set them aside so we can come back to them later.

Next, set up your drill press in whatever manner is appropriate for your equipment, shop rules, etc. If you're at a shared workspace, make sure you don't use the drill press that's set aside for woodworking. You'll get in trouble, and you'll probably ruin it.

We're going to be making several cuts because you can't just go straight for a 3/4" inch hole. Not easily anyway. Pick out several smaller bits that you can use to work up to the final size. I started with a 1/4" bit, and a few others that I found in a drawer of old bits. But don't use overly dull bits, or you'll have a bad day.

With that in mind, lower the table until the pressure cooker fits beneath your first drill bit, and then find some wood and clamps to clamp everything to the table. Get everything lined up so that your final hole will be an inch or two above the bottom of the pressure cooker. If yours has a rounded bottom, like mine, then move the hole an inch or two above the top of the rounded part. Once you get everything lined up, tighten the clamps and lock the table in place.

At this point you should have everything lined up, clamped down, and locked in place. Load up your smallest drill bit and set the drill press to a speed that's appropriate for whatever bit size you're starting with. Now, drill your first hole. If you're using a huge pressure cooker, it will probably vibrate and chatter a lot. Just go slow, and back off if things get too crazy.

Once your first hole is finished, admire your handiwork for a minute, then move up to a larger bit. Keep going until you have a 3/4" hole. Don't forget to lower the drill speed as the bits get bigger.

When you're finished, find a deburring tool and clean up the edges. That last bit probably made a mess.

Congrats! That was the hardest part. It's all Easy St. after this.

Step 4: Install the Bulkhead Fitting

Picture of Install the Bulkhead Fitting

This step is very easy, but it's also your biggest potential leak. Don't worry about that too much now; leak hunting is great sport in the world of vacuum chambers, and there's plenty of time for it later.

  1. Find your bulkhead fitting and two of the rubber gaskets
  2. Remove the nut from the fitting
  3. Put one of the gaskets on the fitting (it should be a tight fit)
  4. Install the fitting+gasket in the hole in the pressure cooker that you drilled in the previous step
  5. Reach inside the pressure cooker and put the other gasket on the end of the fitting
  6. Install the nut on the fitting and hand tighten

Proper tightening of the nut is somewhat critical when it comes to leaks. Too loose and it will leak. Too tight, and it will leak. You want it to be tight enough that the brass makes full contact with the rubber, and the rubber makes full contact with the aluminum wall, but not so tight that the rubber appears to be buckling or deforming.

Once the vacuum pump begins removing air, the outside air pressure will push the fitting against the gasket and make a seal. But, if the gasket is warped, it won't seal properly and you'll have a small leak. If you have a super strong pump, or aren't trying for a very hard vacuum, you may never notice smaller leaks. But if you have problems achieving the desired vacuum, this is the first place to look.

Step 5: Copper Tubing and Compression Fittings

Picture of Copper Tubing and Compression Fittings

It's finally time to put the pieces together.

Cut two lengths of copper tubing. One length connects the fittings assembly to the pressure cooker. The other, longer, length connects the fittings to the vacuum pump. I made the shorter length about 12" long, and the longer one can be a couple of feet. The exact lengths aren't too important. Just make sure you have enough room to get a wrench between the various parts; you'll need the space when it's time to hunt for leaks.

  1. If you didn't already, attach the NPT-to-compression adapter to the bulkhead fitting that you just added to the pressure cooker. Be sure to use the teflon tape.
  2. Connect another NPT-to-compression adapter to one of the ball valves that's attached to the fittings assembly. You probably did that earlier, but if you didn't, then you should do it now. Don't forget the teflon tape.
  3. Similarly, connect the compression-to-flare adapter to the inlet port of the vacuum pump. Don't use any teflon with Flare fittings.

In general, it's a lot easier to install the NPT and Flare fittings first, and then do the compression fittings last. Both NPT and Flare fittings need to be rotated in order to tighten them, which you can't do while they're attached to the copper tube. The compression fittings have a nut for tightening, so you can save those for last.

If you're not used to compression fittings, they can be a bit daunting at first, but they're actually very easy. If you unscrew the nut from one of the fittings you'll see a ferule inside. Don't lose it. Take the nut and slide it onto the copper tube and push it out of the way. The "open" end of the nut should point towards the end of the tube. Next, take the ferule and slide it onto the end of the copper tube, but don't push it any further. It should be right at the end and it should fit snugly, but not tight. Then, insert the tube into the fitting and gently push the tube in as far as it will go. The ferule should seat against the body of the fitting and the tube should slide through the ferule a little ways. Finally, slide the nut over the ferule and screw it into position. You can hand tighten it for now, and then tighten it further when the joint leaks.

Now, using the assembled fittings, and the two lengths of copper tube, connect the pressure cooker and the vacuum pump to the fittings assembly. Use the short tube to connect the pressure cooker to the port on the cross that has the compression adapter. Connect the longer tube from the vacuum pump to the ball valve that you attached the compression adapter to.

The final result should look similar to the first picture above.

Hang in there, we're almost finished!

Step 6: Final Assembly

Picture of Final Assembly

Now is the time for that pressure cooker lid that you set aside earlier.

The gasket that's in the lid of the Miro pressure cooker is very easy to remove. Just give it a gentle tug and work your way around the lid. It should come right out. Check that the gasket is clean, dry, and undamaged.

Next, place the gasket on top of the pressure cooker. Try to get it evenly spaced around the edge. If it's off center it could pop out of place as the differential pressure builds up.

Once you have the gasket where you'd like it, take your sheet of acrylic and place it gently on top of the gasket. Try to keep it centered, otherwise it will get stressed funny. In the best case you'll just get a bad seal, in the worst case it could wear out early, and fail.

Congratulations! You've built a Pressure Cooker Vacuum Chamber!

In the next step we get to turn it on and see what happens.

Step 7: Vacuum Time

Picture of Vacuum Time

Well, we're finally here. It's time to turn on the vacuum pump, and run for cover. Maybe.

Before we actually flip the switch, a few words of caution from our sponsor.

First, be sure to read the instructions that came with your pump. Most, if not all, high vacuum pumps are very finicky and have a special "first use" startup procedure. Follow the directions and get that out of the way before going any further. If you need to, disconnect the pump from the copper tube before running the startup procedure. Once it's ready to go, reconnect it to the copper tube.

Second, high vacuum is serious business. If anything goes wrong there's the potential for a very bad day. With that said, vacuum failures are usually just a leaky joint, and not the least bit exciting. However, we are using a sizable chunk of acrylic here, and acrylic tends to turn into high speed shrapnel when it fails. But, a 1"-thick sheet is nearly bullet proof, so you'd have to do something amazing to get this this thing to break. In all likelihood there's nothing to worry about, but I have to mention it anyway, just to be safe.

Did you put on your safety glasses? Good. Just checking.

If you're ready to go, give everything one last check (did you check the valve positions?), and then flip the switch. The pressure gauge needle should begin moving immediately and the acrylic sheet should visibly compress the gasket. That part is a little surprising the first time, but you'll get used to it.

Within a few seconds the gauge should be showing a serious vacuum. Within a minute or two the action should start slowing down. Eventually the needle will settle on the final vacuum and you should hear the sound of the pump change. If everything went well, you now have a functioning vacuum chamber!

At this point, go ahead and turn off the pump. The pressure should immediately begin rising. The faster it rises, the bigger your leaks. Now you get to begin the never ending task of leak hunting. While the pump is running you can apply drops of the pump oil to the various joints to try to find the leak. If you have an air hose, you can also try pressurizing the chamber and spraying soapy water on the joints (look for bubbles). Tighten any joint that's leaking and try again. Good luck!


RobertC61 (author)2017-09-26

There are alot of comments and wuestions on this thread so i didn't see my question... forgive me if someone already asked. Why three ball valves?

Adilwaseem (author)2017-01-12

Can it take upto 10^-4 milibar

daved8 (author)2016-12-04

seems like you can do all this with a semi-spherical thick glass cake dome, a piece of mdf with a rubber sheet (seal), gauge, tubing, and valves, no? My wife has a thick glass cake dome ... seems like I can do it for under $20 with my vacuum pump and wife's cake dome.

JeffW140 (author)2016-05-28

I aae been looking into making a degassing chamber. In your opinion is half inch thick 12x12" sheet of lexan enough for a 5 quart PC vessel?

MichaelAtOz (author)2014-05-07

Nice clear 'ible.

"make sure you don't use the drill press that's set aside for woodworking. You'll get in trouble, and you'll probably ruin it."

What's the difference with metal v's wood drill press? How can it be ruined?

Also, would it be better to have a few coils on the copper pipe to allow for some movement?

rfox4 (author)MichaelAtOz2016-04-21

most woodworking tools will handle non-ferrous and soft metals fine just remember to take it slow and use either cutting oil or 3-in-1 machine oil often to keep your blades/bits cool and take it slow.

karossii (author)MichaelAtOz2014-05-07

It likely wouldn't be the drill press you need worry about; but the drill bit. As long as you have a multiple speed press, and can swap in a bit suited to the material, there is no such thing as a 'wood' drill press vs 'metal' drill press, etc.

MichaelAtOz (author)karossii2014-05-08

Thanks, I thought so, but am about to buy a drill press and didn't want to go and get the wrong one...

DrPost (author)2015-06-07

Why the acrylic and not the lid that came with it?

rfox4 (author)DrPost2016-04-21

for some applications like stabilizing wood you want to be careful and take the air out of the wood in stages alternating between vacuum an bleeding/resting the air bubbles so you don't over flow your vessel and possible sucking the resin into your vacuum pump. kind of hard to gauge when to let the vacuum off if you can't see what is going on inside.

GurupartapD (author)DrPost2015-07-07

That's what I was wondering...couldn't you could seal the holes in the lid with epoxy or something?

After thinking about it a while, I figure that, depending on what you are using it for, you probably want to be able to *see* inside your vacuum chamber...

Lazy Glen (author)2014-05-06

So - I'm with the other commenter questioning - why drill the pot?

The top you have looks to be intact, and already has a hole in it, (the pressure relief port) as well as a positive locking and sealing method. Plumb the Vac into the fitting on the top and pump away.

This leaves you with a functioning pressure cooker AND a vacuum chamber. Having the Vac port on the top also allows you to use the pot for liquids in either pressure or vacuum mode. (As WyldStyl3 pointed out.)

At the very least, or if the top is missing or failed, put the port in the Acrylic or Lexan top. It can be drilled and even tapped so the fitting threads right in.


PS - if it was a case of tunnel vision, don't feel bad, I do it all the time.

"Look what I made!"

"Cool, why not do it this way?"


XTL (author)Lazy Glen2014-05-06

If you put the port in the pressure cooker lid - you can't see what's going on inside.

If you put the port in the plexi/polycarbonate lid (both brittle and not very strong) then the lid wil crack from the vacuum pressure.

You need to drill through the side.

I'd drill it higher up - for spillage safety.

stratom (author)XTL2016-04-13

Acrylic may crack but polycarbonate will not. Polycarbonate is essentially unbreakable/uncrackable, that is what it was designed for, so you do not need to worry about scratches or drilling holes in it causing stress cracking.

One day when I was working with some Science Olympiad kids we decided to test just how crack resistant polycarbonate is. First test was to bent some polycarbonate until it broke. We were literally able to bend a 1/8th inch thick piece until it was folded over on itself 180degree bend and it never cracked. Not satisfied, we took a 1/4" piece of polycarbonate and a 22 rifle with a long rifle cartridge and shot the plastic. The bullet passed right though and made a neat hole but no cracking. Interestingly, the hole was significantly smaller than the bullet, like the hole closed up some.

I have built vacuum chambers using 2.5 gallon stock lot and a 1/2" polycarbonate top with two 1/4" pipe thread fittings drilled and tapped into the center (about 2 inches apart from each other) and have used it for years. I pull down to less than 10 microns (essentially 29.92" complete vacuum).

Lazy Glen (author)XTL2014-05-07

[quote]If you put the port in the pressure cooker lid - you can't see what's going on inside.[/quote]

Granted - watching materials behave under vacuum can be fascinating.

you put the port in the plexi/polycarbonate lid (both brittle and not
very strong) then the lid wil crack from the vacuum pressure.[/quote]

I do not agree with you here.

Popular Uses for Acrylic (Plexiglas):

  • Motorcycle helmet visors
  • Helicopter Windows, Submarine Windows
  • Spectator protection in ice hockey
  • Police riot control vehicles modifications

I checked the materials list at the top of this 'Ible, that's a 16"x16"x ONE INCH THICK chunk of acrylic. Carefully drilled and tapped, that top is still VERY strong. In fact, from [url][/url]: Because of its transparency, it is also utilized in applications where
it must resist static and dynamic forces, for example, as windows or
shells of pressure vessels under external or internal pressure.

That top is literally bullet resistant. If it were made of Polycarbonate, it would be even stronger, and less brittle, you could take a hammer to it and beat on it with no worries.

We all have a level of safety we are comfortable with, which differs from person to person, I get that. I would be comfortable with a sheet of 3/8" (though it would probably be 1/2" as I have some scraps).

XTL (author)Lazy Glen2014-05-08

Acrylic and polycarbonate have high tensile and impact strength which makes Polycarbonate (Lexan) especially useful for bullet proof windows.

But once scratched they are brittle and crack easily. Try drilling a hole in Acrylic - it shatters easily, you have to drill with a blunt drill. If you drill a hole through acrylic and apply pressure, its is likely to crack - don't take my word for it.

Especially the point about preventing cracks and drilling holes.

Vacuum chambers with transparent lids are highly desirable for outgassing silicones or anything actually. So being able to see in is just not fascinating but neccessary.

bbass408 (author)XTL2015-12-05

put blue painter's making tape on both sides of the hole location. You can use a normal drill bit, but let the drill do the work - only applying light pressure. if you're cracking acrylic when drilling, you're just pushing too hard.

Jason-B (author)2015-09-23

Is there a reason that you decided to use a bulkhead fitting on the chamber as opposed to just drilling a smaller hole and tapping it 1/4" NPT? I am planning on doing a similar project and was planning on drilling an tapping.

asmitha0f989 (author)2015-04-08


I am currently making a vacuum chamber - the only concern i have is that of the thickness of the acrylic sheet i am using. The circular acrylic sheet will be 32cm (12.5 inch) in diameter. with the chamber being smaller at 31cms.

The acrylic sheet is 15mm thick (0.5 inch) will this be thick enough? i will be using a 3CFM Pump to vacuum silicone.

Any help would be great!

Thank you.

GlenJ1 (author)2015-02-19

This is a really good article with heaps of valuabe info. It’s
topical for me as I have just started making my own chamber for degassing
resin. I have attached a photo of some stainless pipe I am making it out of.
The wall is 12mm thick so is over engineered but hey I picked up the pipe and
end cap for nothing. I was going to weld a nipple high up on the side wall but
since reading this I am looking at putting all fittings in the Perspex top. Can
anyone help me with clarification on the following?

Pump – The pump in the article is a “Robin air 3CFM” Is this
a suitable size pump? How has it performed over time?

Perspex – The article displayed mixed reports on whether it
is safe to drill or drill & tap into this material for the required
fittings. Should I drill and tap or drill and glu? Is 1” thick safe to fix
fittings into. Please be specific with grade of Perspex I should use.

Number of fittings required in Perspex – Does this sound
right? 1 fitting to suck out air, 1 fitting for gauge, 1 fitting for pressure relief?

Thanks guys.


GlenJ1 (author)2015-02-19

This is a really good article with heaps of valuabe info. It’s
topical for me as I have just started making my own chamber for degassing
resin. I have attached a photo of some stainless pipe I am making it out of.
The wall is 12mm thick so is over engineered but hey I picked up the pipe and
end cap for nothing. I was going to weld a nipple high up on the side wall but
since reading this I am looking at putting all fittings in the Perspex top. Can
anyone help me with clarification on the following?

Pump – The pump in the article is a “Robin air 3CFM” Is this
a suitable size pump? How has it performed over time?

Perspex – The article displayed mixed reports on whether it
is safe to drill or drill & tap into this material for the required
fittings. Should I drill and tap or drill and glu? Is 1” thick safe to fix
fittings into. Please be specific with grade of Perspex I should use.

Number of fittings required in Perspex – Does this sound
right? 1 fitting to suck out air, 1 fitting for gauge, 1 fitting for pressure relief?

Thanks guys.


racinreaver (author)2014-05-09

You'd actually be running the risk of reversing one of the vacuum pumps and streaming oil into the chamber.

RyanG18 (author)racinreaver2014-12-03

The size you evacuate has nothing to do with running the vacuum pump backwards. To prevent running a pump backwards, you put a check valve in place to not let the vacuum in the system pull air through the pump when you turn it off.

The larger the chamber the longer it takes to evacuate. That's really the only difference.

eviljohnmays (author)2014-11-26

if the polycarbonate is that thick, why not use it for the vac port? The integrity of the pot is maintained, and you are adding fixtures to a flat mount surface rather than a curve. That alone should prevent leaks.

Stan1y (author)2014-09-20

I've used incense sticks in the past for leak hunting you can waft smoke around your joints and see where it goes

craftclarity (author)2014-05-27

I'll be following this design closely.

The paint studio at my school had one of these that was built for silicone molding—it was used to pull air bubbles out of the silicone during the moldmaking process. I might have to build one of these myself, still have a sizeable piece of .5" acrylic from a vacuum bagging project...

jlambert (author)2014-05-06

Just so you will be aware DuPont doesn't authorize the use of the registered trademark name "teflon" when referring to PTFE plumbers tape. Refer to Dupont web site.

whitcwa (author)jlambert2014-05-23

So is DuPont policing us now? Google doesn't want you to use "Google" as a verb. Neither can DuPont nor Google can control free speech.

XTL (author)2014-05-06

a little bit of acetone on a cotton bud also works well. It expands rapidly under vacuum and will show a sudden change in pressure when put near the leak point.

SniperBEAST1515 (author)XTL2014-05-08

very true

SNEHALCHEVLI (author)2014-05-07

What is the use of Pressure Cooker Vacuum Chamber????

SNEHALCHEVLI (author)2014-05-07

What is the use of Pressure Cooker Vacuum Chamber????

cfolts (author)2014-05-06

This could be handy for degassing compounds in small molds, or for vacuum drying something if you wanted to be sure it was bone-dry. Since you're using a pressure cooker, have you considered making it a thermal vacuum chamber as well? I would expect you might need to replace the acrylic with tempered glass, but since you're playing I thought it might be fun

bfoz (author)cfolts2014-05-07

I am toying with the idea of adding an induction heater, but I'm not sure how that would interact with the chamber walls.

DigitalDaveG (author)2014-05-05

What might you use a pressure cooker vacuum chamber for?

Turning small Easter Peeps into BIG Easter peeps!

alcurb (author)DigitalDaveG2014-05-06

Testing your electronics before you send them up on a high-altitude balloon flight

Verifying whether "anti-gravity" lifters work in a vacuum

Groaker (author)DigitalDaveG2014-05-06

At lowered pressure, water boils out at lower temperatures. This means that delicate sauces, which would be ruined at higher temperatures, can be reduced at lower temperatures.

As a biochemist (retired,) I have used these in the laboratory, and wistfully wished for one for my kitchen. Now I have a good design for one.

Thank you bfoz!

Beenay25 (author)DigitalDaveG2014-05-06

Very handy for getting bubbles out of fluids. So useful for moulding latex.

vtgaryw (author)2014-05-07

A nice, simple Instructable. Keep in mind, if you want to use this for liquids (like to use with resins, etc.), you will want to put the inlet on the TOP of the chamber (maybe into the acrylic.)

XTL (author)2014-05-06

Viton tubing is also ideal for joining. It won't collapse under vacuum pressure and can be slipped over two metal(copper) tubes for a neat fit. Its quite amazing material.

Just a little vacuum grease to lubricate. very little.

T_om (author)2014-05-06

I have seen a ton of these conversions and would point out two things. First, drilling the chamber itself (the cooker body) is unnecessary. Not only that, it is also a bad idea to tap the vacuum outlet anywhere near the bottom of a vacuum evacuation vessel. The first time whatever you are degassing foams up to 20 times (or more) its original size, overflows its container, and gets sucked into your vacuum system through that low point, you will see the error of your ways.

ant... (author)2014-05-06

Ive made lots of these myself, as for the ring that holds the vacuum I now use a 5mm closed cell foam with self adhesive backing. Its never let me down.

I had to move onto a clear chamber because I use electronics within my vacuum chamber. A whisk to help remove air bubbles, because they can just froth up and hold, and I have pumps to move the resin into molds.

The pressure cooker I now used for pressurising my mold to shrink the bubbles in the epoxy then I heat it to 80c and let it cure.

You can remove bubbles from most molds in a vacuum chamber, small molds are especially hard to get the air bubbles out.

WyldStyl3 (author)2014-05-06

Why not put the bulkhead fitting in the acrylic top? That way you still have use of your pressure cooker if you ever need it. Also, you can use the vacuum with liquids in the chamber.

chuqui2000 (author)2014-05-06

Hi! you should share a video with the vacuum working, that would be great!.. thx

and7barton (author)2014-05-06

One use is to remove air bubbles from clear resin after you've stirred in the hardener. If you are casting blocks, you don't want it spoiled by air bubbles.

danielandersen2 (author)2014-05-04

Use old Easter peeps...

bfoz (author)danielandersen22014-05-04

I couldn't find any!

Ravidow (author)2014-05-04

Great idea. Just out of curiosity, besides bleeding of the vacuum to remove plexiglass, what do you use the extra ball valves for?

bfoz (author)Ravidow2014-05-04

An extra port can be used for a lot of things, and the extra parts weren't too expensive. Sometimes I just go overboard when buying new toys :)

I imagine if you were making your own nixie tubes you could use the extra port to fill the chamber with whatever gas goes in the tubes. Or maybe connect a second vacuum pump to get a lower final pressure (DIY diffusion pump?). Or...

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