DIY Vacuum Purging Chamber

To perform some of the desirable alchemy with cannabis essential oils, requires some sort of vacuum chamber that you can control the heat and vacuum levels in, as well as see what you are doing.

These are readily available as vacuum desiccators and vacuum ovens, but all are pricey, so how about just building your own?

We already have a glass desiccator with a hot plate inside,and picked up a new used vacuum oven, but alas the temperature controls are ineffective in the low ranges that we operate, so we are in the process of refining its controls.

More on that subject on a separate thread, but this thread is to show how we punted when the vacuum oven capacity that we had counted on, eluded us, with meds to process backlogged.

To that end, we used a old 22 quart Mirror pressure cooker that was gifted to us, and after removing the gasket, we tossed the lid.

I then drilled a 1/4" pilot hole through the side wallwrapper, about 2.5" below the top flange, followed by a 3/4" bit, to enlarge the hole to fit a 1/4" NPT brass bulkhead fitting.

I then inserted the bulkhead fitting through the side wallfrom the inside out, installing a gasket on the inside flange, and tighteningthe nut and lock washer on the outside of the pot.

To this I added a close nipple, a cross, with two 1/4"ball valves, and two 1/4" MPT to 1/4" flare refrigeration hose fitting. One for the vacuum pump and the other for the vacuum gauge hose.

As it is temporary, and we needed it immediately, we reused the existing gasket, and made a new lid out of a 1" X 16" acrylic plate. At -29.9" Hg gauge, there is about 1/16" lid deflection in the middle, so a thicker plate would be better to reduce high cyclic fatigue.

If it were permanent, we would have a new Viton gasket cut by Paramount, or Gaskets Unlimited and use 1 1/2" polycarbonate, for the lid.

Hee, hee, hee, after telling me that they didn't have any, and after having them cut the 1" acrylic plate, I found a 22" X29" X 1 1/2" Polycarbonate remnant at Multi Craft Plastics, which I scored for $72. It has one 6" hole in one corner, but that is $2/lb for bullet proof polycarbonate panels, like those used at teller windows. Snicker,s nark, snort, more projects to come!

Here are pictures showing how we made and how it turned out. We are able to easily control the temperature with an outside hotplate and reduce the pressure to -29.9 with one of our 6.2 cfm single stage AC vacuum pumps:

awesome thread. seeing how simple it is, I wish I never spend 115$ on my chamber and built one myself for 10$ and 5$ worth of simple fittings that I probably have in the truck.. why did you use a bushing instead of a 1/2 x 1/4 swedge in the cross?

1. how are you able to get 29.9, are you vaccing at sea level somehow??

2. your pump/fittings/everything else was able to hold such a strong vacuum that your 1" lid started to suck into the chamber? guzias, are you reading this??

3. those cracks you seen in my lid. you cant even feel them with your finger, and the lid is 1/2" thick or more. another member here has the exact same chamber, and his lid isnt cracking. why could that be?

vacpurge said:

awesome thread. seeing how simple it is, I wish I never spend 115$ on my chamber and built one myself for 10$ and 5$ worth of simple fittings that I probably have in the truck.. why did you use a bushing instead of a 1/2 x 1/4 swedge in the cross?

1. how are you able to get 29.9, are you vaccing at sea level somehow??

2. your pump/fittings/everything else was able to hold such a strong vacuum that your 1" lid started to suck into the chamber? guzias, are you reading this??

3. those cracks you seen in my lid. you cant even feel them with your finger, and the lid is 1/2" thick or more. another member here has the exact same chamber, and his lid isnt cracking. why could that be?

Click to expand...

We are less than 100 feet above sea level.

14.7 psi X 113 sq/in =1,661 pounds of force on the plate, so some deflection is to be expected. I prefer to minimize that, because the constant flexing back and forth will cause stress cracks.

1/2" is too thin for that much pressure and modulus of elasticity. It is heat and flexure that is causing yours to fail. It is possible that it is a bad run of acrylic, or that you have cycled yours more times than your friends. A thicker plate will flex less and be less prone to high cyclic fatigue.

youre talking about atmospheric pressure on the top of the lid??? (side note science lesson for you bored stoners... take a news paper. 15x15 inches well say. 225 square inches. times that by atmospheric pressure (14.7 psi) and youve got 3307 lbs of force on that sheet of news paper. take a meter stick, or a stake post, and slide it under the news paper.. leave it sticking out about a foot. now if you karate chop that stick. there is so much force holding down on the news paper that you can break the stick, even though its just being held down by newspaper. cool eh)



will my lid eventually break? I started to see these cracks after about a week of use. if heat is bad now, wait till its summer and real hot here!

I thought ofthis exactly! My dad has a pressure cooker and I thought I could take out the gasket/valve/exhaust or toss the lid and put 1" plexi for a lid drill and regulate according... Voila vacuum chamber... Just need the oump

vacpurge said:

awesome thread. seeing how simple it is, I wish I never spend 115$ on my chamber and built one myself for 10$ and 5$ worth of simple fittings that I probably have in the truck.. why did you use a bushing instead of a 1/2 x 1/4 swedge in the cross?

1. how are you able to get 29.9, are you vaccing at sea level somehow??

2. your pump/fittings/everything else was able to hold such a strong vacuum that your 1" lid started to suck into the chamber? guzias, are you reading this??

3. those cracks you seen in my lid. you cant even feel them with your finger, and the lid is 1/2" thick or more. another member here has the exact same chamber, and his lid isnt cracking. why could that be?

Click to expand...

i have read ittttttttttttttttt. wow, heheee, im happy my vac pro is still kicking..

i attempted the pressure cooker idea, i couldnt find one for less than $70, that was just the cooker alone.. i'll keep my eyes/ears open though though.. the hardest part is finding a gasket that will seal the lid to the chamber..

Id imagine its not too hard to make your own gasket?

Guzias1 said:

i have read ittttttttttttttttt. wow, heheee, im happy my vac pro is still kicking..

i attempted the pressure cooker idea, i couldnt find one for less than $70, that was just the cooker alone.. i'll keep my eyes/ears open though though.. the hardest part is finding a gasket that will seal the lid to the chamber..

Click to expand...

The gasket from the Mirror pressure cooker worked as was, but Paramount Supply or Gaskets Unlimited can supply one from other materials.