Cannabis produces phyto cannabinoids in a carboxylic acid form that are not orally active at least at the CB-1 receptor sites, because they don’t readily pass the blood brain barrier in their polar form.

To enable them to pass the blood brain barrier, they must first be decarboxylated, to remove the COOH carboxyl group of atoms, which exits in the form of H20 and CO2.

Decarboxylation occurs naturally with time and temperature, as a function of drying, but we can shorten the amount of time required considerably, by adding more heat.  The more heat, the faster it occurs, within reasonable ranges, and in fact occurs spontaneously when the material is burned or vaporized.

There is another mechanism at play however, which suggests that we need to control the decarboxylation temperatures carefully.

When we heat cannabis to convert the THCA and CBDA into THC and CBD, we are also converting THC to CBN at a faster rate.  At about 70% decarboxylation, we actually start converting THC to CBN at a faster rate than we are converting THCA to THC, so as you can see by the following graph, after about 70% decarboxylation, the levels of THC actually start to fall sharply.

That of course means that the CBN also begins to rise and the medication is becoming more sedative.

Thank you Jump 117 for this excellent graph!

Decarboxylation Graph-1-1

Decarboxylation graph

Another fly in the ointment, is that we can never know for sure exactly what the starting state of decarboxylation is, so the times at temperature shown on the graphs are an average.

We can’t expect dry material placed in an oven at any given temperature to be that uniform temperature throughout instantly upon placing it in a heated oven, nor know for sure the state of decarboxylation by simple observation.

Decarboxylating plant material, also alters the taste (roasted/toasted), which some find less agreeable, and of course decarboxylating also evaporates away the smaller Monoterpenes and Sequiterpenes alcohols, phenols, ketones, aldehydes, ethers, and esters.

The good news is that it is dirt simple to monitor the state of cannabis oil decarboxylation placed in a 121C/250F hot oil bath, because you can watch the CO2 bubble production.

Just like the curves suggest, CO2 bubble production will proceed at its own observable rate. By keeping the puddle of oil lightly stirred on the bottom and in the corners of the pot (I use a bamboo skewer), so as to keep the bubbles broken free and floating to the top, you can tell exactly when the bubble formation suddenly tapers off at the top of the curve.

That is the point that we take it out of the oil for maximum head effect, and we leave it in until all bubbling stops, if we want a more sedative night time med.

Here are a couple pictures of what oil looks like when boiling off the residual butane.  Residual butane or alcohol produces larger, randomly sized bubbles, and is fully purged, when they cease.

I am seemingly missing the middle picture of the CO2 bubbles, so I will add it later, but the second picture shows what fully decarboxylated oil looks like.

Residual solvent bubbles above:

Quiescent oil.

304 responses to this post.

  1. Posted by charlie on September 29, 2014 at 7:55 PM

    quick question on decarbing. My oven(house oven) only goes down to 170, how long should I bake for? I want high thc, not cbd


  2. I was able to find gold information from your articles.


  3. Question. When doing IPA solvent extractions using rotovaps can vacuum ovens be used to pull out the remaining solvent AND decarb the oil? It seems that high grade vacuum ovens can reach the temperatures and uniformity needed to activate the THC/CBD. I have searched but couldn’t find a solid answer either way. I am trying to learn and have a basic understanding but am hung up on how to scale up the decarb process when making concentrated oils.

    Thank you!


    • Posted by mdd4890 on September 25, 2014 at 8:30 PM

      I don’t know but I have purchased both and will try to give an update. The rotavap is great. That and a hot plate work well..can evaporate the solvent and not go over 80° the whole process then use the hot plate to decarboxylate. I’m waiting on the vacuum oven to arrive and plan to test it out soon. My question would be how hot and for how long should the process take for let’s say an oz of oil in one of those stainless steel containers that is pictured above to decarboxylate without converting too much thc to cbn? Considering that the solvent was evaporated from the oil without ever going over 150°F. I have read that thca converts to thc at 240°F so we would want to at least get it up to 240/250 right?


  4. sorry, I am lost. you say … “as you can see by the following graph, after about 70% decarboxylation, the levels of THC actually start to fall sharply.”… excuse me, where exactly in the graph is that “70%”? and where exactly, in which curve “THC falls”? thanks so much


    • Posted by MattMatt on September 1, 2014 at 8:06 AM

      If you see the line for 145c it get’s to 15mg/g (about 70%) of THC and then drops after about 7 minutes, the 122c line drops at about 70% too but after nearly 30 minutes, the lower temps we don’t actually see reach 70% in the time frame shown on the graph as it only goes up to 50 minutes. The drop indicates that THC is degrading to CBN at a faster rate than the THCA is converting to THCA. Longer times at lower temps has the conversion of THCA to THC is much slower and takes more than an hour to get to those levels and THC will start to degrade to CBN before it even gets to 70%.
      The graph took me a while to understand too and it is frustrating that it doesn’t observe the lower temps for longer so we can see how their curves progress, but basically it is saying that it is hard to convert all THCA to THC with out degrading THC to CBN. GW Pharmaceuticals have a patent on cannabis as a cancer treatment (20130059018) which details that different heating stages helps get maximum decarboxylation with minimal degradation to CBN. I forget the exact times and temps but I think it was something like 30 minutes at 100c then 30 minutes at 120c. Check out the patent and it will give the exact method they use. The only way to be sure is to get it tested and in the absence of testing facilities you can either make sure decarb is 100% but end up with some degradation of CBN, or avoid CBN but end up with unconverted THCA. Depends on what you are treating but for cancer full decarb is recommended as THC is most potent against cancer while CBN also has some value in that regard, while THCA is not considered to be cancer killing based on current evidence, though is believed to have some anti cancer effect


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  6. […] Green Dragon veröffentlicht, für den man nur 3,5 Gramm Marihuana zermahlen, bei 100°C im Ofen decarboxylieren und dann das Gras mit 750ml Alkohol in einen hitzeresistenten Sahnespender geben muss. Dann dem […]


  7. The CO2 release referred to here can be seen clearly in my canna-butter video:


  8. […] a nitrous-powered Green Dragon that requires nothing more than grinding up an 1/8 ounce of pot and decarboxylating it in the oven at 212 degrees for about an hour, then putting the decarbed bud and 750 ml of booze […]


  9. Posted by klaatu on July 28, 2014 at 6:44 PM

    Greetings GW. I have been blessed by your shared wisdom in these matters for a long time now, well before this site gathered so much of it together, and added so immensely to it. You have scattered cogent posts among various older forums, and it wasn’t so conveniently arranged as it has now become. Thank you for your persistent contributions, exemplary vision and truly public service

    I haven’t commented or written ever before, I typically work pretty silently in the back of the back room, but now your well sustained open spirit is infecting even me. I would be very grateful to hear what you might say in clarification of something having to do with all this, should you wish to…

    “many of the terpenes (d-limonene, linalool, mycrene, a-pinene etc.) are evaporated off when you decarboxylate cannabis oil”

    I have seen this statement, or one like it, many times, here and elsewhere. I find this more than somewhat confusing, since the boiling points of these terps are all quite high, well above normal decarb temps:

    Limonene Boiling point 176 °C (349 °F; 449 K)
    Linalool Boiling point 198–199 °C
    Myrcene Boiling point 166-168 °C
    Pinene Boiling point 155 °C (311 °F; 428 K)
    Terpinolene Boiling points a: 173.5-174.8 °C

    With the exception of Pinene, these are all higher temps than the boiling point of THC itself

    Some time ago, after quite a bit of study on an extraction issue, I found an old patent from the 50s that dealt with *removing* terpenes from essential oils used in the fragrance industry, because they would break down during the distillation or storage and produce off smells:

    “natural oils contain terpenes and sesquiterpenes which, in general, oxidize readily in the air with the development of unpleasant odors and flavors”

    Some of the wiki articles on these canna terps also mention this degradation. Humulene is especially reactive with atmospheric ozone in sunlight, with a lifetime of a couple minutes.

    This decomposition of terpenes results from exposure to heat, light, and oxygen. This is why they are so ephemeral, they decompose very readily, especially with heating, like during decarb. It would not seem that they vanish rapidly due to evaporation at these temps that are quite below their boiling points.

    also from this patent:

    “The terpenes may be recovered … by distillation. Vacuum distillation is preferred to minimize decomposition of the terpenes.”

    If the terpenes are heated enough to boil/evaporate, then they have already decomposed instead, unless it is done under vacuum at much lower temps.

    They do vaporize to some degree at temps below their boiling points, like water slowly disappearing out of a drinking glass at room temp. That’s why we smell them. But their woeful loss during these extraction and decarb procedures does not appear to me to be due to evaporation, like so many enthusiasts seem to think, and say.

    This patent also makes note of ‘terpenophilic solvents’, down near the bottom, in the claims. Non-polar hexane is very terpenophilic. Other solvents are non-terpenophilic, like acetone, which they used to extract everything but the terps.

    My feeling on all this is that the absence of satisfying terp levels in various procedural results is much less because they evaporated, and much more because they decomposed along the way, or perhaps weren’t all that present to begin with because of the use of a non-terpenophilic solvent

    Kind regards. Comments invited


    • Morning Klaatu!

      An interesting theory, and well presented! Good job!

      I pulled the vapor pressures of the monoterpenes in question and some are indeed suspiciously low given their aromatic nature, lending credence to the theory that what we are smelling, is not just molecules escaping low intermolecular forces and colliding with our noses, but the degradation products of the terpenes that were cast off, colliding with our noses.

      I copied the patent in question, and will review it in greater detail, as well as ask our biotech Joe to join me in analyzing the issue.

      More after doing so. Thanks for the insight!

      Peace, GW


      • Posted by JPene on August 25, 2014 at 12:22 PM

        Just curious if you have any follow-up for Klaatu…I am also interested in this matter. Many thanks in advance!


  10. Posted by Joe C on July 24, 2014 at 6:43 PM

    Ive been searching the interwebs in order to create a specific oil to aid a family friend with type 1 diabetes… From what i can gather, CBN is what i’m trying to amplify. With that in mind & based on the fact TCH converts to CBN if decarb’d longer, how long would you leave it @ 250 – 270 F ?? Cheers, Joe


    • Posted by Kyle on July 26, 2014 at 2:47 PM

      Just a thought, but you may be able to find pure CBN extracts online since this isolated chemical isn’t scheduled. I know a friend of mine was able to order big syringes full of CBD oil from amazon.


      • Posted by Joe C on July 27, 2014 at 4:56 PM

        I live in AUS so i’m not sure the same applies here, but will look into it. Also i’ve heard that CBN alone is not the best as one also requires the many other components of cannibis plant. Correct me if i’m wrong as i’m a cannabis oil noob!


        • Posted by Kyle on July 27, 2014 at 5:45 PM

          According to that chart after about 4+ hours at ~260 degrees F there would be very little THC which would imply that the THC has mostly converted to CBN. You could also look up the temperature at which CBN is destroyed. If its a much higher temperature you could keep heating for even longer maybe to get an even higher yield of CBN. Just a thought.


          • Posted by MattMatt on September 26, 2014 at 7:19 AM

            Can I ask where you are getting 4 hours from when the chart only goes to 50 minutes? Above 140c for an hour seems sufficient to make sure CBN is maximised

  11. What about bubble hash, how could you monitor it’s decarb. rate? Just by color or is there a more specific way of judging it’s percentage of decarboxylation? I feel like over-heating and surpassing the 70% might be a big problem in most edible makers recipes at the moment, or at least I’ve personally noticed a lack in potency with hash infused edibles. What’s different about the process with a water extract versus chemical?


    • Posted by MattMatt on July 21, 2014 at 6:16 AM

      It is harder to judge when Hash is finished decarbing, same goes for plant material. Oil you can tell by the bubbles. Hash I wouldn’t know. I think if you cooked it for between 30 to 60 minutes at temps between 110 and 130c then you are pretty certain to get your hash decarboxylated to a near full degree with out too much over cooking. But the precision is easier to gage with oil because you can use the activity as an indication of decarboxylation.
      Water extractions are generally less efficient that solvents because THC is not water soluble so it is not actually dissolving into the water, it’s more like just being washed off in a more crude manner. Solvents that require heat to boil off will result in some partial decarboxylation, where as cold extraction solvents like Butane will not result in any decarboxylation, but both methods require additional cooking. As for cooking hash or plant material, the best you can do (to my knowledge) is cook it for the appropriate times and temps and hope that decarb is achieved with out too much overcooking.


  12. Posted by JLVanta on July 11, 2014 at 2:43 AM

    Incredible stuff on this site! Love it!

    I have some questions as a newbie, I have seen many videos starting from the original RS Video, to this one I found on a Dutch site quite impressive and easy for everyone to do…

    None of them decarboxylat the oil and its seems to work anyway…

    Some Chemical Phd said that while decarboxylat translates your THCA CBDA –> THC CBD…it also destroys or decreases (partially or completly dont know) the other good stuff…to name a few (tetrahydrocannabivarin, myrcene, caryophyllene, d-limonene ,linalool, pulegone,cineole ,a-pinene,a-terpineol,terpineol-4-ol,p-cymene apigenin, quercetin, cannflavin A etc..)
    I am really sorry for not providing a link to thois theory, because I lost the bookmarks, so do you think that there is some thruth about it?
    I want to make some oil for my Mother with Chronic Pain, would like to do it right…

    Thanks to all!


    • Posted by MattMatt on July 11, 2014 at 10:37 AM

      It is true that many of the terpenes (d-limonene, linalool, mycrene, a-pinene etc.) are evaporated off when you decarboxylate cannabis oil, and obviously all the cannabinoid acids are lost as they are converted to the neutral cannabinoids. However it is the neutral cannabinoids that are most important for treating many conditions, especially cancer.
      Terpenes can be sourced from other plants as they are present in many things. Citrus fruits contain d-limonene for example, Linalool is in mint and cinnamon, Myrcene is found in thyme and lemon grass. So you could make other extracts for terpene content if you wish to supplement the cannabis oil.
      Another option chosen by many is to make both raw and cooked cannabis oil and take both so that you can get decarboxylated cannabinoids from the cooked oil and cannabinoid acids and terpenes from the raw. The video from the link you provided did involve some heat so would likely have been partially decarboxylated. Partial decarb is also something that people opt for as partially cooked oils contain activated cannabinoids and cannabinoid acids, along with whatever terpenes remain.
      Personally I think you are best either cooking oil fully or leaving it completely raw and simply taking both if you wish to utilise both, as oppose to partial decarboxylation. As partial decarb is harder to dose as you don’t know how much decarboxylation has occurred. Where as if you have fully cooked oil you can dose it more accurately and then take raw oils as a supplement to the treatment.
      For chronic pain I honestly do not know which is better, so maybe someone else could advise. Cooked cannabis is definitely better for cancer as the actives cannabinoids like THC and CBD are far more effective against cancer than cannabinoid acids or terpenes. And I would expect decarboxylated cannabis to be better for chronic pain, but I have heard that many people have found raw to be better for chronic pain. So you might need to try both and see which works best.
      For most conditions, including cancer, the most ideal scenario is to have large amounts of both raw and cooked cannabis oil. But for most people access is limited and choosing the optimum for their conditions is necessary. As I said for most conditions cooked cannabis is more potent, but there are some conditions that respond better to the cannabinoid acids and some patients who have reported better relief from raw.
      So for your mother you may need to experiment a bit and try her on both. She will be able to take much larger amounts of raw oil with no psychoactive effects, where as cooked will require her to start with very small doses and slowly build up a tolerance.
      Like I said if you go for fully decarboxylated and wish to add some terpenes to make up for what is lost then you can make other extracts for terpenes or add things like turmeric, citrus fruits and ginger to her regime.
      Hope this is of help to you.


      • Posted by margaret on July 29, 2014 at 11:22 PM

        If the oil was made a few days ago and one wasn’t sure if it was properly decarboxylated can u put it in the oven days later and decarboxylate?


        • Posted by MattMatt on July 29, 2014 at 11:50 PM

          Yes. If you are ever in doubt if oil is fully decarboxylated you can heat it to 110c and see if there is activity on the surface. If there is not then the oil is done, if there is then keep cooking until activity stops. Some people stop cooking just before all activity stops to avoid degrading any THC to CBN. But such degradation is minimal if you stop cooking as soon as activity stops and is better to have fully decarboxylated oil with a little CBN than half cooked oil with more THCA than THC


  13. […] carboxylic acid (THCA), which becomes THC when exposed to heat or UV light. Because of this decarboxylation process, most of the THC you experience when smoking cannabis is actually THCA in the flower […]


  14. […] always remember that eating decarboxylated marijuana produces a far stronger effect than smoking the same amount of raw plant material, […]


  15. […] always remember that eating decarboxylated marijuana produces a far stronger effect than smoking the same amount of raw plant material, […]


    • Posted by MattMatt on September 26, 2014 at 7:28 AM

      I’m not sure that is true. Smoking a few puffs or cannabis will get most people high. Eating that same quantity, even fully decarboxylated, will probably not result in any psychoactive effects. It is true that eating cannabis results in stronger effects that often last longer than smoking once you get into the larger quantities, especially as smoking any amount of cannabis will where off in the same time period (usually about 3 hours) where as increased amounts ingested can result in longer lasting effects. But the minimum required to get high from eating is usually larger than what is required from smoking


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