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DIY Vacuum Purging Chamber

Gray Wolf

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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 wall wrapper, 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 wall from the inside out, installing a gasket on the inside flange, and tightening the 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 3/16" 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" X 29" 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, snark, 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:
 

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JColtrane

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Nice set up GW! Having the ball valve to close off vac I think is key. I've been following your advice on the bubbles, and not worrying so much about seeing all the small bubble gone. I really think I have been killing terps by keeping a hard vac for multiple hours. Again, you've helped me ... thanks:tiphat:

Anyways I'd make a suggestion on your pot ... perhaps put some sort of filter on the inlet of your pot. I've done this to mine to eliminate any dust getting on the oil.
 

Gray Wolf

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Nice set up GW! Having the ball valve to close off vac I think is key. I've been following your advice on the bubbles, and not worrying so much about seeing all the small bubble gone. I really think I have been killing terps by keeping a hard vac for multiple hours. Again, you've helped me ... thanks:tiphat:

Anyways I'd make a suggestion on your pot ... perhaps put some sort of filter on the inlet of your pot. I've done this to mine to eliminate any dust getting on the oil.


Thanks for the good thoughts bro! I would say from the sample that you brought to class, that you have been paying attention to details!

Good idea to add the filter to the backfill valve!
 

Gray Wolf

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Nice, I need to build me one.

Hardly gets any cheaper if you cruise Goodwill for the pressure cooker and shop for plastic remmants at the plastics crafts and manufacturers.

In this case, the only thing I had to buy was the acrylic lid, as the rest came out of garages and drawers. You can also find hot plates cheeeap at Goodwill as well!
 
J

JimmyRow

Perfect timing, I'm ordering my vac pump tomorrow or the next day, and I was just getting on to research this topic.
Great write up GW. Thanks
Btw, spent a large portion of today on skunkpharm, think I'm gonna start w/ the lil terp next month.
I really appreciate you dropping the knowledge.
 

midwestHIGHS

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Thanks for posting this thread GW! This will sure be help to the many who are over spending on an easy do it yourself project.

Thanks again, you do so much for this community!
 

Gray Wolf

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More experiments and progress.

Went looking for another pressure cooker to make another chamber from, for son Waywardwolf and discovered that the new Mirror pressure cookers no longer have a flat bottom. Neither did the Presto we looked at.

That means we need a source for the pot, that doesn't involve searching Goodwill stores, for those with more money than time.

We whacked the 1 1/2" Polycarbonate sheet, that I scored for $2/lb, into two lids. One to replace our 1" Acrylic lid and the other for Son I. Refreshingly, there is no observable deflection at -29.5" Hg, while the 1" still deflected about 3/16".

We went through all our existing hot plates in an effort to control the temperature in the 85F/115F range, and even picked up a griddle from Bimart, that works somewhat with a trivet between the hot plates and an Oil Slick pad inside to help diffuse the heat.

Alas, it still had excursions that were too hot, so I ordered a couple reptile cage heating pads, which Skylighler posted on forum X and which he is able to control that range accurately using a light dimmer switch. They arrived last night, so I should know how well they work today.
 
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J

JimmyRow

I have a thermostat for my germination mat that holds up to 108°f, but that's a little shy of your goal.
 

Gray Wolf

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Soooo, how about heat in the 85/115F range, way below what most hot plates and griddles control at?

We've tried several different hot plates, with and without trivets and pads to dissipate heat, and ran across a slick set up forum X, posted by Superly and using two layers of reptile mats to generate the heat, controlled by a simple light dimmer switch.

Hee, hee, hee, works pretty slick! After cutting them to size, I put a towel under them and then put two layers of towel over the top surface, but cut out a big hole in the top layer through which the pot sat, resting on the heating mat.

Here was the test run of Cheese!
 

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MrAwder

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This is great. Just went ahead and ordered 2 heat mats. Should have a spare box/outlet and dimmer. Does the temp stay pretty constant once it's dialed in?
 

hammalamma

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Soooo, how about heat in the 85/115F range, way below what most hot plates and griddles control at?

We've tried several different hot plates, with and without trivets and pads to dissipate heat, and ran across a slick set up forum X, posted by Superly and using two layers of reptile mats to generate the heat, controlled by a simple light dimmer switch.

Hee, hee, hee, works pretty slick! After cutting them to size, I put a towel under them and then put two layers of towel over the top surface, but cut out a big hole in the top layer through which the pot sat, resting on the heating mat.

Here was the test run of Cheese!

Just got mine! Be sure to get the connectors. Cant wait to try em!
 

Gray Wolf

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This is great. Just went ahead and ordered 2 heat mats. Should have a spare box/outlet and dimmer. Does the temp stay pretty constant once it's dialed in?


I don't see a driving need for a spare controller, but check the output voltage of the dimmer switch, as some have excessive drop and don't put out close to the original 120 VAC input voltage.

Yes, mine keep steady temperature.
 

Gray Wolf

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Adding inlet filter on the make up air, to keep dust out when back filling.
 

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Gray Wolf

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Sorry I just meant that I should already have those spare items laying around to build one ;)

Are the 2 mats wired together into one plug?

Yes, I rewired them that way, and after shortening the mats, I resealed the cut end of the mat using electrical mastic tape.
 

MrAwder

Member
Just wanted to drop back into this thread and mention my results with the "Best Value Vac" chamber from ebay (http://www.ebay.com/itm/3-Gallon-Va...381&pid=100012&prg=7787&rk=3&sd=221224476283&)

Was working great for a while but lately seems to be losing vac pressure after maybe an hour. The neoprene gasket is noticeably thinner than when I first got it. It seems many hours under vac has compressed it and this is possible leading to seal that is not 100%. I have contacted the seller to see if there is a good way to replace or modify the gasket to improve the seal.

Any ideas here?
 

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