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.

392 responses to this post.

  1. Posted by tavon on February 28, 2015 at 9:05 AM

    Decarboxylation – When making cannabis oil for treating late stage cancer it is important to understand decarboxylation. Cannabis in raw/unheated form is primarily THCA, which converts to active THC through heat and time. While some very slow and gradual decarboxylation does occur at temperatures as low as room temp during drying and curing stages of weed preparation it is not until higher heats are encountered that all THCA is converted to THC. If you are making cannabis oil you need to make sure the oil is cooked sufficiently to complete full decarb. Raw cannabis is very beneficial and cannabinoid acids like THCA, along with naturally present terpenes, are believed to be very beneficial with possible anti cancer properties. However, it is active THC, and CBD, that has the majority of clinical and anecdotal evidence supporting its cancer killing effects. So, based on what is currently known, cannabis oil that is most potent in THC content is likely going to be the most potent medicine for curing cancer.
    Raw cannabis in the form of juices and unheated oils are beneficial too and would make a great addition to someone’s treatment, but should not replace cooked cannabis oil, and often require much larger quantities for therapeutic value. Raw or partially cooked oils will contain a wider range of components including cannabinoid acids and terpenes, which are lost when oils are fully cooked, but THC is the most essential cannabinoid for fighting cancer so make sure you decarb your medicine properly to maximise its potency.
    The Rick Simpson method only guarantees partial decarb from the rice cooker stage, and while full decarboxylation can be achieved with the use of a coffee warmer or candle warmer it can take some time to complete this process and other gentle heating devices may not be hot enough. Many of the solvents used have boiling points below the optimum temps for full and rapid decarb. If you do not have a coffee/candle warmer, of even if you do, it is recommended to put your oil in the oven at 110 to 130 degrees Celsius for about an hour. Visible bubbling will cease when the solvent and water, along with volatile terpenes, are boiled off. But you will see very small pin prick explosions on the surface of the oil during decarboxylation. When this has ceased and there is no activity on the surface of the oil at temps of 110c or above, then you know that decarboxylation is complete. While you want to ensure that temperature does exceed 110 degrees Celsius for decarb, it is also advised to stay below 140 as temps above 140 can lead to a loss of THC through vaporisation (157c)or degradation to CBN.
    In an ideal world everyone would have access to both raw and cooked cannabis in a well controlled manner, but in this world where oil making can be expensive and risky it is best to make sure your medicine is as potent as it can be to maximise its potential.
    This info is for anyone unaware of Decarboxylation or confused about how to achieve it.


  2. Posted by Blaz on February 28, 2015 at 2:24 AM

    Mahaffia, I am also wondering that, i have always decarboxylated it in the process of cooking, but i am thinking that it might be better if you put it in the oven at about 110˙C for at least half an hour, and then slowly and safely extract with with a solvent (no danger of overheating) But I am worried that it may effect the quality of the product. Not sure though….


  3. Posted by MattMatt on February 27, 2015 at 4:05 AM

    All cannabinoids start out as cannabinoid acids. So yes, decarbing is necessary to convert THCVA to THCV too. I don’t know the exact temps/times but I would expect full decarboxylation (till activity stops) to mean full decarboxylation of all acids to their neutral counter parts


  4. HI, I’m wondering about decarbing THCV for edibles. Is it necessary for THCV or can you get the full effect of the THCV without decarbing? Also are times & temperatures for THCV decarbing (if needed) the same as THCA?


  5. Posted by mahaffia on February 18, 2015 at 12:54 PM

    What are the pros and cons of decarboxylating the material first, and then extraction with glycerin?


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