By Troy Ivan
Like most people, when I first heard ‘DECARBOXYLATION’ I had no idea what it meant and the word itself confused me, but the sound of science grabbed my attention, I had to know more. I was relieved to learn a short form of the big word existed and is commonly referred to as ‘decarb’. The more I researched the more confusing the concept and process became. Everyone had different stories, experiences, opinions and references to a wide verity of conflicting recommended temperature and time combinations. Some people even claimed decarbing was a myth and completely unnecessary. The vast majority of available information was unorganized and unreliable, stoking my motivation to work on this experiment to find some clarity on different decarb methods. There are far too many methods and time/temp combinations for me to cover all, so I chose to compare a few of the most easy to perform in a normal home kitchen. Before we get too far ahead of ourselves, let’s build a better familiarity with the different important aspects and implications of performing decarb.
BASIC SCIENCE OF DECARB
Being familiar with the basic science involved with decarboxylation can be very helpful in sorting through all the internet noise surrounding the topic. Let’s start at the beginning with the natural form of tetrahydrocannabinol (THC) that develops in the trichomes of the cannabis plant as it grows and matures, THC-A. You will hear many people refer to THC-A as the “acid form of THC”, meaning it has an extra carboxyl group that differentiates it from THC. Notice that the word ‘carboxyl’ is the root of “decarboxylation”, which simply means to remove the carbolic acid group. When the carboxyl group breaks away carbon dioxide (CO2) is given off and the molecular mass of THC-A reduces by about 12% becoming the smaller molecule known as THC. This size relationship can be seen in one of the most common equations used for measuring total potential THC in a cannabis sample [THCtotal = (THCA x 0.877) + THC].
The change from THC-A to THC is a natural process that begins immediately when the plant is harvested and continues very slowly over years depending on how well the cannabis is prepared and stored. The process can be accelerated by soaking cannabis in a solvent like ethanol, completing the conversion in just 6-8 months, or hyper-accelerated with the application of heat. Decarb is influenced by three specific variables: temperature, time, and environment. Changing any one of the three variables will affect the extent of decarb achieved. By applying varying degrees of heat you can fully decarb cannabis at different rates. Low heat will take longer, high heat works faster, and the temperatures used for smoking or vaping cause instantaneous conversion. As time passes decarb continues, so with the comparison of any two periods of time, with everything else equal, the longer time period will always result in a higher degree of decarb. Environment is a more opaque and less concise consideration but very important. Open air, ambient temperature, and exposure to sunlight will cause oxidation, conversion and degradation of both THC-A and THC. The environmental influence on the cannabis I used in this exercise had already taken place prior to it coming into my possession, making it a fixed variable across all the samples used for each method. Therefore, I will treat environment as a constant and remove it from the discussion in comparing the different methods in this exercise and concentrate on temperature and time.
Everyday I see people seriously obsessing over the simple science of decarbing and meticulously analyzing every factor for fear of ruining their cannabis if they make an error. Simple decarb questions in some groups often break out into internet brawls. If you take a step back and think about it, you can see there is very little precision happening in your kitchen compared to a lab, so it might be best to treat the decarb process less like a lab procedure and more like a kitchen activity. If the starting material came from a source other than your own grow, you have no real idea how it was stored, how long it’s been out, how much sunlight it’s taken on, and the real state of decarb that’s already taken place (environment factor). Even if you did grow, cure, and store it yourself, in most cases it would be difficult to know precisely. Furthermore, controlling the temperature of your appliances, especially cheap appliances, will be far from laboratory specifications but they will be good enough to do what we need them to. So, my general advice is to relax a little bit, take what I’ve written here under advisement, give it a little thought, take your best shot, believe in chaos theory, stay lifted, and move on.
COSTS ASSOCIATED WITH DECARB
The quality of terpenes and amount of decarb present in the cannabis you consume are both dependent on the same three variables (temp, time, environment) but are at odds and inversely correlated. Meaning, any factor that furthers decarb comes at the expense terpenes. The loss of terpenes during decarb is a concern for most people, but it’s not an easy problem to solve since anything that facilitates decarb degrades terpene quality. Maintaining low processing temperatures can help preserve some of the most volatile terpenes to a minor degree and decarbing with a containment that can trap them can also provide a small degree of salvation, but for the most part you have to accept the fact that when you choose to decarb you will have substantial terpene conversion and loss. Luckily, one of the most exciting recent developments in the cannabis industry is the availability of isolated terpenes and terpene profiles that can be reintroduced to a decarbed concentrate to make up for any loss and in some cases make the concentrate better than it would have been originally.
Another cost of decarb that causes concern is the conversion of THC to CBN. Only a small amount of elevated CBN can cause a difference in the psychoactive effects of cannabis. CBN conversion takes a bit of effort, and you have to over process a decarb by a decent margin, but the good news is, even if it happens it’s not the end of the world. People often mistake the effects of CBN to an elevated degree of being ‘high’, when in reality it’s not more ‘high’ but more sedated. In fact, many people who need a very strong ‘chill’ factor or heavy sleep aid seek the help of the CBN component.
This study is incredibly well done and interesting in many ways, if you have a chance to chew on it a bit I highly recommend it. It discusses the science of many aspects of the process, including nullification of CBN development under vacuum, temp/time combinations for both THC and CBD, and other interesting stuff. Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High-Performance Supercritical Fluid Chromatography/Photodiode Array-Mass Spectrometry.
WHY DO PEOPLE DECARB, DO I NEED TO?
To determine if decarbing is necessary for your intended use and needs decide if you require the benefits of THC-A, THC, or both. To begin exploring this, let’s look at the difference in the psychotropic effects and the potential benefits of using THC-A and THC. The most obvious difference between the two is that THC-A does not induce psychotropic effects, the feeling of being “high”, while THC does when ingested orally or inhaled. THC-A has become very important as an anticonvulsive, controlling and stopping many forms of seizures, anti-inflammation, pain relief, nausea, depression, overall well-being, and has shown positive signs in the treatment of prostate-cancer. It can do all of this without making people feel high.
On the other hand, THC has strong psychotropic effects that some people love and others have difficulty with. The difference in psychotropic effect is a result of the smaller relative molecular size of THC compared to THC-A. The smaller molecular size allows THC to pass through the blood-brain barrier and attach to the cannabinoid receptors in the brain, creating the ‘high.’ The smaller THC molecule has been demonstrated to have an increased ability to kill cancer cells, work as an anticonvulsant, bronchodilator, appetite stimulant, strong pain reliever, sooth nausea, help with PTSD, induces sleep when nothing else works, along with a number other general health benefits.
The choice between using THC-A or THC is generally pretty clear-cut, as already discussed, but a couple of brief comments on how that choice relates to the various modes of consumption like oral ingestion, suppositories, topicals, smoking and vaping might be helpful. The decision to decarb for oral ingestion typically hinges on two considerations, desired benefits and one’s tolerance for psychotropic effects. Suppositories are typically understood to have no psychotropic effects if used properly so either THC-A or THC can be used. Having said that, suppository effectiveness is hotly debated and I would recommend reading my post “The Cannabis Oil Suppository Debate: Personal Testing & Results”for more information. Topicals are not directly ingested into the body orally nor through the lungs so either THC-A or THC can be used, without psychotropic effects.
When it comes to smoking or vaping there’s an interesting consideration concerning conversion efficiency and bioavailability. In most cases, the rule of thumb for cannabis that will be smoked or vaped is that decarbing prior to consuming is not necessary because it occurs automatically when combusted or vaped. With combustion and smoking of flower high temps are easily achieved and all the desired constituents will be consumed, making prior decarbing unnecessary. Vaping and dabbing with quality equipment allows for precise temperature control to target cannabinoid and terpene components, attain very high conversion and dial in desired effects, using temps to control the intensity of the high delivered. With higher quality controllable vaping equipment decarbing is also usually considered unnecessary because you can preserve all the terpenes in your concentrate with high cannabinoid conversion efficiency. On the other hand, there are people who like to do low-temp dabs to enjoy rich flavors and avoid the possible adverse health issues associated with high-temp dabbing. In this case, it’s possible to lose a good percentage of cannabinoids to low conversion. The low conversion problem can be solved by decarbing the material, and adding back any terps that were lost in the process, creating a high cannabinoid conversion and high terpene dab. Likewise, there are many people using vape cartridges with low power batteries that operate at low temps that don’t provide reliable THC conversion, hence much weaker effects than desired. To insure a more potent delivery of THC some people choose to use decarbed oil and added terpenes to make vape cartridges.
To recap, when deciding if you need decarb or not there are just a few considerations. First, determine if you desire THC-A, THC, or a combination. Second, consider your form of consumption and if higher conversion is necessary. Third, for your use, are the costs of decarbing worth the benefit? Lastly, can the risk of potential terpene loss be mitigated by adding terpenes back later?
For this exercise I prepared some outdoor GSC flower broken up by hand and separated into 7g bags for a control sample and for each test. I chose a 7g sample size because it’s representative of what many people may decarb at home for personal use and the results will be consistent with the larger volumes when executed properly. When processing larger amounts you must make sure the cannabis is not in a thick or compressed layer that would hinder heat transfer and cause unequal and incomplete decarb.
NOTES ON USING AN OVEN FOR DECARBING
Ovens are notoriously unreliable for temperature accuracy, and to my disbelief, during this exercise I found my Across International vacuum oven was actually off nearly 30°F whereas the oven in my kitchen was spot on. Here are some things you can do to make using the oven more reliable for decarbing:
- Before using an oven for decarbing, determine if the internal temperature of the oven matches the temperature you intend to base your decarbing.
- To measure the accuracy of your oven temp you can put a measuring cup of water in the oven with a thermometer or use an inferred temperature gun to see what the oven temp measures.
- Remember the areas of the oven that deliver heat will read much higher than the rest of the oven, if possible measure the temperature of the rack, grate, or pre-heated cookie sheet.
- When checking the internal temperature of the oven or preparing for decarbing, before measuring the temp or beginning a decarb, allow the oven to settle for about 20 minutes after it indicates it’s up to temp.
- If the observed temp in the oven differs from the actual setting you can either note the difference and adjust the setting accordingly to achieve the desired temperature. For example if your target temp is 240°F but the oven only measures 220°F, try setting 260°F and see if it settles at 240°F and if it does use that correction going forward. The other option is to use the measured oven temp as is and adjust the decarb time accordingly.
- If a cookie sheet is being used, make sure it’s preheated with the oven and up to temp before putting anything on it to process.
I chose to compare methods that range from the traditional use of an oven, a couple of gadgets, and a couple of methods I worked up myself. First we’ll look at using the oven with foil tents, sealed canning jars and, vacuum packs, then the sous vide, steaming, and the Ardent Nova. In comparing each method and the respective results I was looking for high THC conversion, low CBN conversion, possible terpene preservation advantages, ease of use, odor, and general advantages or disadvantages of each.
Oven – Foil Tent
- 240°F for 60 minutes – 100% THC conversion, no CBN conversion
- 260°F for 40 minutes – 99.6% THC conversion, no CBN conversion
This is a simple method, just put the cannabis on some foil and fold it loosely like a tent then fold over the ends to completely seal. The folded shape doesn’t help control the odor much, but it does prevent the cannabis getting overly toasted as it would without the foil protection. This was the easiest of all methods and both samples were effectively fully decarbed. The only real downside to this method is there is a decent amount of odor, there will be no secrets about what you are doing.
Oven – Vacuum sealed pack
- 240°F for 60 minutes – 100% THC conversion, no CBN conversion
- 260°F for 40 minutes – 100% THC conversion, no CBN conversion
After doing the foil tent, I thought a vacuum sealed pack would perform the same function but better. I had never seen nor heard of this being done so I wasn’t sure if the plastic would melt and ruin the cannabis or not, but I only had one way to find out! I used a Food Saver unit to vacuum seal the cannabis and planned to place it on a cookie sheet for decarbing. I preheated the cookie sheet in the oven so it was up to temp along with the oven when the vacuum packed cannabis went in. After the time was complete removing the samples showed that the CO2 release from the process made the bag puff up a little and there was moisture in the pack that wasn’t there to start. The pack worked as planned and trapped anything that had evaporated then it re-condensed on the cannabis or the surface of the pack as it cooled. It wasn’t odor proof but it was a lot less than the foil tent.
A great advantage of this method is being able to capture the vapor and everything remained in the pack. When making butter, an infusion or extraction I would be sure to gather whatever was collected on the surface of the bag by using the pack to do part of the infusion or ethanol wash for extraction. I liked this method, it seemed to work very well, and achieved full decarb.
Oven – Mason Jar
- 240°F for 60 minutes – 100% THC conversion, no CBN conversion
- 260°F for 40 minutes – 99.5% THC conversion, no CBN conversion
I’ve been developing a feel for working with sealed mason jars for decarbing for a while. Like the vacuum pack test, evaporated terpenes are trapped in the jar and re-condense on the glass surface as long as you don’t open the jar until it’s fully cooled. Then, you can use the jar to do your infusion or extraction and collect all the desirables that would have otherwise been lost. After the jar cools I put it into the freezer, and use the same jar for doing frozen qwet (Cannabis Oil QWET Extraction Battle of the Wash: Dry Ice vs. Freezer). The big bonus to this method is there is no smell at all, it’s all contained in the jar.
This process has a couple operational considerations that require attention. First, a cool jar will require ramping time and uncertain heating, so it’s important to pre-heat the jar. The jar can be brought up to temp along with preheating the oven. When it’s time to put the cannabis in the oven, remove the pre-heated jar from the oven, quickly load the cannabis into the jar, secure the lid on the jar, and place it back in the oven. This process also provides the added advantage of creating a natural vacuum seal later when it cools and before going into the freezer. Second, the jar shouldn’t be filled too much, it’s best to leave quite a bit of head room to allow even heating of the material. I usually don’t fill the jar more than 1/3 full at most. If I do put more in I rotate the jar half way through the process to ensure even heating and add a few minutes to the total time to make up for opening the oven and losing some heat. Third, I lay the jar on its side to expose as much surface area as possible. Lastly, glass in a dry heat environment requires caution and you must use your own judgement on if it is safe or not. I have not had a single failure to this point, but it’s important to understand the possible risks of breaking glass due to temperature changes before trying for yourself.
Sous Vide (gadget) – Vacuum Pack
- 191°F-194°F for 120 minutes – 93.3% THC conversion, no CBN conversion
I was really looking forward to using the sous vide, regrettably it ended up being a fail, but not by fault of the process. I believe the process is sound and will work great at lower elevations. The sous vide I purchased claimed a range up to 199°F which I thought achievable because water here at 5,000 feet boils at 203°F, however, it failed to heat above 191°F on its own. I added boiling water and it was then able to maintain about 194°F for the remaining time. The original plan was to perform both 90 minute and 120 minute tests, but with the low temperature limitation I opted to do only the 120 minute. I’ve heard numerous great reports about this technique and I believe if I were at a lower elevation where water boiled at a higher temperature it would have achieved full decarb. I think this assumption is supported by the results of the next method, steaming, and the temperatures used there.
The operational considerations are limited with this method. The only difficulty comes from keeping the pack submerged in the water, especially as it begins to bloat. I used magnets to hold it down, but any form of weight will do. One word of caution that gives me a little concern with this method, I didn’t clean this material meticulously so there were some very small but tough stems in the sample. When the packs vacuum sealed the small stems must have punctured some of the packs because the vacuum seal was lost. The leaks don’t appear immediately but slowly over time, so if you are going to use this method prepare the vacuum sealed packs in advance and let it set overnight to confirm the vacuum seal is sound or you may end up with water in your pack. Lastly, I have been cautioned by chefs that use these often that the cheaper consumer models are not very reliable or durable, and that can be upsetting when you consider the cost of this gadget.
Steaming – Vacuum Pack
- 203°F for 90 minutes – 97.3% THC conversion, no CBN conversion
- 203°F for 120 minutes – 98.1% THC conversion, no CBN conversion
When I started seeing the sous vide being used for decarb I thought, why not just steam a vacuum sealed pack? The temperature of steam is at least that of boiling water, and maybe just a degree or two higher with the lid in place to create a minor amount of back pressure. As already mentioned, at 5,000 feet elevation water boils at about 203°F so I hoped this temperature would perform better and overcome the difficulties I had with the low sous vide temps. I was very happy with this process, there was a very slight odor, and it was no more hassle than the sous vide but required no costly gadget. Like the sous vide, if I lived at a lower elevation where water boiled around 212°F, I’m sure this would have been a blinding success.
I’m guessing this same process can be used in an Instapot. I have not tried it yet, but there is a consideration that makes this even more interesting. While decarb isn’t effected by pressure the boiling point of terpenes are, so if you decarb in an Instapot under positive pressure can you preserve more terpenes? This is a great question I am looking forward to answering at a later date (in the meantime, if someone else can try it, test it, and let us know, that would be outstanding!).
Ardent Nova (gadget)
1 cycle – 100% THC conversion, slight elevation of CBN .09 to 0.15
I’ve been experimenting with the Ardent Nova trying to understand all the claims of this gadget for over a year now. I’ve run it with many samples, and I’ve even taken it apart to examine the components and structure, and it seems to be pretty much the same tech as a rice cooker. It has two temperature sensors that run against a timed algorithm and that appears to be the extent of it. It’s simply a heated cylinder however the claims I’ve seen are extensive: 1) decarb THC with precision, 2) decarb CBD with precision by running two full cycles, 3) decarb plant material as well as oil, 4) use it for infusion.
To me these claims seem overstated and mislead the average consumer to believe it actually does more than I believe it does. I mentioned earlier that decarbing with precision in the kitchen is quite difficult for a number of reasons, but I see the Ardent solving one of the difficulties by providing a reliable and consistent heat, and if that is what they mean by ‘precision’ then that’s great. However, decarbing THC, CBD, plant material and oil all precisely, in terms of the different requirements for each of those it’s just not a reasonable claim in my opinion. Looking back at this study Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High-Performance Supercritical Fluid Chromatography/Photodiode Array-Mass Spectrometry you can see the difference in the curves used at low temp decarbing. The Ardent uses a low temp for a very long time which as you can see from the graphs flatten with longer times at lower temps. While it might be a ‘good enough’ I don’t consider it to be precision, and it’s certainly a result that can be replicated for free using other methods. The other precision problem is the inability to differentiate between the amount of mass or density of material loaded into it, meaning it can’t tell if there is a little or a lot loaded, which should be accounted for by the temp ramping algorithm but doesn’t seem to change in the operation when I run a ¼ ounce or more. On that same point, the inability to distinguish between plant material and oil mass has its own problems for precision, the inability to observe the oil or stir the oil during the process builds in decarb inefficiency and ignores the fact that the oil may have already sustained ample decarb during the extraction process depending on what equipment was used. So, my impression is that this gadget can be used for all of the claimed applications, but I’m not buying the ‘precision’ argument outside of possibly holding a constant temp and following its own algorithm. Lastly, the suggestion to user the appliance as an infusion appliance as well as for decarb is kind of funny, it’s obviously not designed to be both.
The processing time for 7g was about 2 hours. It was 2 hours where I didn’t have to worry about monitoring it and paying attention to it, that was very easy and worry free. In fact, after about an 1 hour 45 minutes I just went to bed because I was tired of waiting for it to finish. This method provided the most toasted sample in this whole exercise and showed signs of being over processed with a not so pleasant aroma. This was the only method I tested here that had a small volume capacity limitation.
Some people really love this gadget for the ability to simply push the button and walk away without having to monitor or think about if they are getting the best result possible. With a little bit of thought and minimal effort you can achieve the best possible result without spending this kind of money and having the volume restriction. I’ve tested this gadget thoroughly and it’s my least favorite of all the methods presented here.
I’m so happy to have had the opportunity do all of these tests side-by-side and present them together, I’ve been wanting to do this for a long time. It’s clear to me that every one of these methods provides nearly the same outcome with some minor differences, and I think this shows that at home decarb is a lot more forgiving and robust of a process than it’s usually recognized as. I’m confident that all of these techniques can easily provide full decarb and require very little effort. Having said that, the methods employing water for the heat source do not appear to be suitable for higher elevations.
To choose the method that best suits your needs think about what tools you already have at your disposal, processing volume needs, how much time you have, if the odor is a factor, if you want to try to recover what terpenes may be present, your value of convenience, and your budget for unnecessary but convenient gadgets. For me the pre-heated jar method was a clear winner, but everyone will have their own favorite process and I’m confident that whichever one you choose you will achieve great results, so stop worrying about it and just enjoy a stress free decarb.
APPENDIX: DECARBING OIL
I feel it necessary to include a short comment on decarbing oil and concentrates. The chemical action of decarbing and converting THC-A to THC is the same with cannabis plant material and concentrates. Applying heat for an amount of time to instigate the breaking off of the carboxyl group is the same for both. In this exercise my focus was on decarbing plant material, but I often decarb concentrates and oil as well. If you want to give this process a try, simply place the oil or concentrate in an appropriate container and apply heat between 220°F-260°F until the bubbles stop forming. There are a few important points and cautions to be aware of with this process. First, when a concentrate is heated up to decarbing temperatures it will be the viscosity of a runny liquid, so it must be contained or it will run off any mat or flat surface and make a terrible mess. Second, as it comes up to temperature tiny CO2 bubbles will appear and they can expand rapidly so make sure you leave lots of room for expansion because it can expand enormously. Third, it’s very important to stir the oil throughout the process to facilitate an even decarb. Lastly, once the very small CO2 bubbles stop forming you know the decarb is complete. My preferred method for this is to use a heated magnetic stir plate with a thermal couple.