Decarb under pressure to retain terps?

Has anyone done any work on decarbing their extracts under pressure to retain terpenes?

I’ve tried it on a small scale with some success, and it looks like it might be time to try it on a larger scale.

If my new still recovers in anything close to the time frame the manufacturer suggests it will (100gal in 2hrs at 35C!), then I’ll have to add a decarb step for my tinctures. Doing so at pressure to keep the terps might even give me a viable pen juice (I’m running decarbed EHO in the pen I’m using now).

My current assumption is that the manufacturer has been inhaling solvent fumes, but even 8hrs at 35C isn’t going to fully decarb my material, so I’m going to start playing with decarb under pressure again.

How about chemical decarb? @Acicular?

Edit: as shown here, my equipment manufacturer was not blowing smoke up my ass, and the math says recovery time should be about 2hrs.


I don’t know if it actually works, but I saw these folks at a trade show and they seem to be doing something similar. I’m not really sure I get the need for both Nitrogen and Helium, maybe that’s the proprietary part. In any case they claim to retain all terps during decarb by pressurizing the gas head while heating the oil.

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I’ll take that as a vote for at least trying it (again).


I also can’t figure out why they would need helium as well.
Except maybe that someone has a patent for using just N2 :stuck_out_tongue:

I guess it’s possible that N2 is cheaper, but not quite inert enough for heating terps? seems unlikely. (is there a chemist in the room?).

I doubt they’re doing anything requiring pressures only He can provide.

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Much like terpene mixing under pressure clever! Does it pressure cook them under heat/pressure? I use pressure to help condense terps but never tried a decarb in this manor. Does it affect the decarb conversion in anyway? Awhile back I knew an extractor that would wrap material in tinfoil and cook 0psi in oven to retain terps, it worked on all its ghetto glory apparently

I would assume a vacuum lowers the boiling points of everything in the solution, not just the solvent.


wrong thread?

Pressure not vac…

Yeah, probably. That’s why the folks at harvest direct are using inert gasses in there. Pressure cooking with O2 around isn’t going to do the terps any favours.

care to elaborate?

sure. but I’ve got no data on how yet, and I haven’t gone looking for anyone else’s yet. presumably trapping the CO2 will have some effect on the reaction at some concentration. perhaps not at the concentrations I’ll see. don’t know.

based on the diagram on harvest direct’s website, presumably going above the 40 PSI at 100C I would expect to see if I left a little ethanol in there is appropriate. I can safely manage 120PSI with parts on hand.

might have. not sure I understand how.

I made a couple of tries, I was happy with the results.
used a coffee warmer and 4"x6" tri-clamp spool. Should have put a gauge on there. will next time.

real issue is that I’ll need some way of determining % decarb, and my bioassay team isn’t quite well enough calibrated. they can all tell 50% from 100%, and 10% from 0% if I dose them right, but their 90% to 100% is pretty iffy. :smile:

I figure I’ll throw $160 of TLC kit at it and see how far I’ve gotten. then re-evaluate. I think I could calibrate an old school UV/Vis spec to distinguish THC/THCA and CBD/CBDA, but working that up just to get the decarb solved seems like the long way around. it is still attractive long term if I can’t swing an in-house HPLC

Edit: CBDa decarb kinetics and more (PDF in comments) thanks @slooty

Edit: these critters are about $15k and look fairly useful to have around. essentially mini-LC with Diode array detection and some embedded analytics.


Ahhh we meet again, explain this to me, your running straight eho under pressure to retain terps, then running this straight in your pen,

I’ve got couple different recipes gathered up, and about 5 different packs of carts to try, couple different pens, I’m hoping for success as the Wax liquidizer was nice but I’m hoping for something more like the medicinal quality pens ocpharm etc I don’t know any other companies yet, ashamed to say, but in my area those things arent around yet. I’m hoping to get me great juice recipes… Thanks to all and for all the help bro

currently running decarbed EHO. the viscosity was lower on this specific strain, and it works well.

I am theorizing that retaining more terps during decarb, may lower the viscosity, and up the taste on other strains.

I’ve got a BHO that I decarbed this way (once upon a time) that also works in the carts that keep coming in the mail as samples.

the CBDA decarb paper cited above shows better kinetics and less losses in a sealed reactor (flame sealed glass vial). Even without finding similar data for THCA, is seems worth the effort to repeat my small scale experiments…but figure out exact times this time around.

pretty sure I can pull the jacketed receiver on my PX1 into duty for the first scale up attempt too. Success there would warrant a new pressure vessel.

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Okay can I ask this would not decarbing it retain more Terps to begin with and make a more runny substance would that not help for the whole viscosity of the cartridge and since it’s getting hot enough through the atomizer doesn’t it Decarb it? I’m still new at all this though I’m learning

nope. THCA is higher viscosity than THC. think shatter.

EHO is waaaay more likely to form glass like shatter than BHO.
safe & easy to make at home too (also legal here in OR, unlike diy-BHO).

We decarb for edibles, the stuff I’m using in my pen was destined for tinctures in MCT. The in-house organoleptic testing my team did gave it great reviews, but it’s a deep red, and won’t make it to market in a cartridge. The input material was so purple it was almost black, in the past I’ve gotten blond Butane extract from this strain, so I believe I picked up pigment with the ethanol. it’s pretty, just not blonde. the market want’s blonde.

I could decolorize it. but first I want more terps. and less oxidative damage. hence the proposed experiment.


N2 provides an inert nitrogen blanket to prevent oxidation & degradation, the He is less dense so it will carry the CO, CO2 out of the oil and thru the N2 blanket, allowing removal of the reactive byproducts.


It sounds more plausible than anything I’ve got. Would such a layering work?

Wouldn’t the gasses just mix as the He bubbles reached the liq/gas interface?

I know we’re not working with ideal gasses, but I though N2 wasn’t bad, and He was about as good as it got.

N2 and CO have similar molecular weights, the He2 is lighter so would elute out the top. I am assuming the design is to use the He2 as a mobile phase, and N2 as the non mobile blanket


N2 also denser than CO2 or CO

Twenty plus years experience as an organic chemist. I worked in the Environmental Organic Analytical World until 2014. I have extensive GC experience as well as some of the better instruments, C13 and H1 NMR, FTIR, UV-VIS and a ton of extraction experience. Not sure why Helium other than it may be more inert than Nitrogen. Might be an issue of purity but we were able to obtain 5 9’s which is 99.999% pure.

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then why both? Cause N2 is cheaper? But is lacking what?

First place I go is high pressure. Which I just don’t buy. Their cartoon vessel is too big in relationship to the tanks to take much more than 200psi if my cartoon physics is any good.

I can fathom an inert blanket. I understand getting better terp retention at higher pressures. I could even get behind removing reaction products to improve kinetics if it seemed like it would help (not sure it does).

I just don’t understand a nitrogen blanket failing to mix with the He and entrained CO2 bubbling through it.

I might could be convinced though.

Interesting, so maybe they are actually sparging with hot He2 and using the nitrogen as a blanket to separate out the CO2 for reclamation from the top with the He2 while keeping the terps down.

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This idea is reasonable, but there are a few very important caveats and notes that you must know before doing it:

  1. Pressure does not significantly affect the decarboxylation reaction kinetics, so it should proceed at normal temperatures and times, even under pressure. With enough pressure, you may find you can get away with slightly lower temperatures, but there are severe limitations on that, as described below. Of course any pressure applied should be devoid of reactive compounds like oxygen, lest they react with your material, especially under pressure! Nitrogen (N2) is relatively inert and inexpensive, as it is very abundant in our atmosphere. Besides inert gases like argon, N2, (please don’t waste helium on this), the only other gases in the headspace above the reactants should be the vapors of the terpenes and other volatile compounds naturally present in the resin.

  2. Pressure DOES affect other reactions! Terpene decomposition and cannabinoid isomerization are the two most important for you to know about for this application. Decomposition and isomerization (and really all reactions) have a certain activation energy that must be reached above the steady state energy of the reactant materials, before they can react and come to rest at a state of energy lower than where they started.
    For example, because Δ8-THC exists with lower potential energy than Δ9, the Δ8 is the naturally preferred conformation between the two. That said, Δ10, Δ10a, CBN, and many of the isomers & derivatives in between are lower energy than Δ9 or Δ8.
    So, activation energy is an energy “hill” that reactants must climb before a reaction can proceed spontaneously, sliding down the hill, as it were. This energy can be provided in the form of heat (very commonly), pressure, light energy of effective interacting wavelengths and sufficient power (amplitude), stirring (mechanical energy), and other forms, depending on the type of reaction.

  3. A catalyst is a chemical that can reduce the activation energy for the desired end resulting rxn. To accomplish this, the catalyst may temporarily and reversibly interact or react with a reactant or even the solvent, thereby changing the starting conditions and thus activation energy of the reaction, but without permanently changing the catalyst, itself. Unless something “poisons” your catalyst, it will not be used up in the reaction, so very small quantities are needed. However, the rate of catalysis is usually proportional to the quantity of catalyst present… so more catalyst = more reacting happening at the same time.
    One example is a Brönstead acid (H+ or proton donor) is a catalyst for isomerization of Δ9-THC to Δ8-THC. This is so common that many folks believe acid is required for isomerization to occur, but it most certainly is not!
    Lest we forget, many reactions that are commonly done by catalysis can still be done without a catalyst, just by applying sufficient energy. Pressure can give the resin compounds that extra boost they need to isomerize or decompose. So be wary!

  4. Catalysts can be used to your advantage for the decarboxylation reactions of cannabinoid acids, without affecting (or even hopefully increasing) the activation energy of undesired rxns. As long as your crude or solution thereof is totally devoid of water (anhydrous), I usually recommend dry magnesium oxide (MgO) as a decarboxylation catalyst, though other alkaline earth metal oxides and some transition metal oxides will also work, to varying degrees. Since decarboxylation is a pseudo-first-order rxn, the catalyst lowers the required temperature to achieve a given rate of decarboxylation. For example, based on my observation, just a teaspoon or less of MgO per liter of crude resin appears to let the THCa and other cannabinoid acids decarboxylate at a rate typically seen at about 280-300°F, at only 180°F.
    MgO has the ancillary benefit of neutralizing acids present, even under the requisite anhydrous conditions, thereby effectively eliminating some or all of the plant acids present that could otherwise catalyze isomerization. However, that benefit uses the MgO as a reactant, not a catalyst, so if there is too much heat-ionizable acid present in your crude, it will “poison” (use up) your MgO decarboxylation catalyst.
    I think you will find decarboxylation catalysis “essential” (heh) to retaining your terpenes, with or without inert gas pressure.
    In any case using MgO, you should be forewarned that adding too much MgO to your crude will cause it to coalesce, turning the MgO into a blob of concrete at the bottom of your decarboxylation flask or beaker, even with stirring. So err on the side of caution and only add that maximum of 1 teaspoon per liter of crude!

@McWest I am fairly certain that for a given temperature, CO2 is more dense than N2… though I may just assume that based on the fact that CO2 is heavier than air.

Ultimately, I think catalysis to lower your decarboxylation temperatures will be the most crucial implement toward terpene retention in the resin. Helium is very inert, but it is also a valuable resource that is ever-depleting from our planet until we perfect controlled nuclear fusion of hydrogen for energy production. N2 will work just as well for this purpose.
I think a sealed atmospheric pressure blanket of N2 devoid of oxygen should suffice, since I have heard that even 10 psi can jumpstart isomerization. Any additional pressure should be provided by the partial vapor pressures of the volatile compounds in the resin at decarboxylation temperature. If you do decide to use N2 pressure above atmospheric, please let me know if it caused any isomerization… this would be indicated using HPLC standardized with Δ8-THC as well as the usual Δ9-THC, but even a “before and after” test of just the Δ9 would tell you if the amount was diminished or not. Good luck! :blush: