Butane Honey Oil extraction, or BHO, is one of the methods used to extract cannabis oleoresins and oils using butane as the solvent. There are many theories on the best way to accomplish this, but here is the formula the skunk pharm uses to extract the crude oleoresin and refine it into a pristine absolute.
As most of our extracted oil goes into oral meds, we also decarboxylate ours. This process is based on the 252F curve shown in the attached graph, which I copied from Jump 117.
Butane performs one of the cleanest extractions of cannabis, because it a relatively non polar solvent, and therefore extracts few water solubles. It however produces a lower yield than alcohol extraction, because of being more circumspect in what it extracts.
N-Butane, also known as R-600 refrigerant, is non toxic enough to be used as a food propellant. Those who have been led to believe that it is highly toxic, owe it to themselves to compare the MSDS on Google to drinking ethanol.
One does have to be selective as to source however, as all butane stove fuel must by law have methyl mercaptan added for leak detection. Besides adding odor, Methyl mercaptan adds an unpleasant taste and has a sensory threshold of only 2 parts per billionth, so it difficult to impossible to eliminate once it is present.
R-600 refrigerant or cigarette lighter fuel butane is therefore normally used, as they do not have mercaps added. There are none the less a plethora of wives tales surrounding lighter fuel butane, for the most part designed to separate the unwary from their money.
Specifically, there is much controversy surrounding the number of times the butane has been refined and the level of contamination present. The contamination present is in the form of oleaginous waxes, which in butane is paraffin. Paraffin is non toxic enough that the MSDS doesn’t even list an LD-50 rating and it is used to seal jelly jars.
The refining to get it out has nothing to do with toxic properties, but the fact that expensive lighters have small orifices that are easily clogged by wax. The number of times the butane has been refined also says nothing about how much wax is left, so it means absolutely nothing. Just Madison Avenue verbiage to sell the same product for more money.
One supplier cleverly added the title “Near Zero Contamination” to all the brands that they produce, and it certifies that the residual contamination is less than 50PPM. In point of fact, they actually measure less than 15 PPM contamination, as does many competitive brands with less ostensible refining.
Skunk pharm uses Lucienne 4X butane because it tests under 15 ppm, same as the “Near Zero Contamination” 5X brands and we can purchase it for under $25 a case of (12) 300 ML cans.
Butane is highly flammable, so let us next talk about safety. It goes without saying that smoking around a butane extraction is asking for a disaster, but I have literally grabbed the hand of folks starting to light up because they “forgot” where they were at and what they were doing. May I suggest that you leave your lighter and smokes somewhere else when you are doing extractions.
Same with your cell phone!
Wear no synthetic fabrics, including your socks, because static electricity sparks probably ignite more butane unintentionally than bone headed smokers.
We use a fan to disperse the butane rapidly so as to keep it from pooling. Butane is heavier than air and will collect in low spots given its own devices. We use a plastic fan so that no sparks are created by a piece of gravel or other hard material passing through the fan blades.
In dry cold conditions, we add a grounding strap to our cans, so as to not draw static electricity sparks between the can and the column.
As most of our extracted oil goes into oral meds, we also decarboxylate ours. This process is based on the 252F curve shown in the attached graph; I copied from Jump 117 on ICMag’s forum.
The first question is why use a BHO technique to extract the resins, instead of just boiling the material in alcohol to get the greatest amount of extracted material?
The answer to that is that because butane is relatively non polar, it doesn’t extract the water solubles like chlorophyll and plant alkaloids, as well as the plant waxes and vegetable oil. Butane produces one of the cleanest extractions, albeit at the lowest yield.
On average we have extracted about 18% oil by weight from bud, but as low as 12% and as high as 25%.
The first wash will usually extract 75 to 80%, leaving the balance for the second after repacking the column. The second extraction will be more sedative and less heady. If you use a hand microscope, you can easily see when the trichome heads are gone and the stalks look like wet fur.
The first step in the process is to get as much water as possible out of the material.
A fresh material BHO is possible, and is hands down the most flavorful extraction tested by the panel thus far, but this procedure covers both fresh and cured material that has been cured to about 15% water content. 15% is a lot of water, so unless we reduce the water content even further, we will be extracting some water solubles, despite butanes low polar activity.
We dry our cured material even further by spreading it on a cookie sheet and baking it in a 200F oven until just frangible when rolled between the finger and thumb. We then scrub it through a wire mesh pasta strainer, using a leather gloved hand and firm pressure, so as to minimize the amount of fine particles generated.
The stems will be left behind, which I encourage you to save for a different extraction, and make a killer topical out of them. If you leave them in the extraction, they will leave some of their flavor behind.
We never, ever, use a blender or coffee grinder to reduce material, because it produces a lot of ultra fine powder that makes it through conventional filters.
Next, while it is still warm, we seal the material in a jar or baggy until loaded in a column.
If we are running fresh material, we simply cut it from the mother plant and freeze it as is. That ties up the water as ice. We take it out of the freezer and place it in a plastic bag, which we pummel to break into small pieces. We load those pieces into an extraction tube and return to the freezer. We also place the butane in the freezer and process the material, once both the plant material and the butane stabilize at 0.0F.
If it is cured, desiccated, and reduced material, we simply load it into a column and do not bother to freeze it.
Sooo, let us talk about columns. A column is a long narrow containment that allows a solvent to be passed though it using either gravity or pressure. In the case of a butane column, we do both.
If you Google Cole-Palmer, you will note that n-butane is not compatible with all of the materials available to build a column from. Some plastics like PVC are not suitable for instance because the butane leaches out the constitutes, which we prefer to not have in our meds, but in some part because of impurities in the butane that may attack them given extended usage.
Glass and borosilicate (Pyrex) work well, as does 300 series stainless steel, and as does copper, with the caveat that the column must be meticulously kept clean of copper oxide, which produces fume fever when welders weld copper based alloys with insufficient respiratory protection. If you do not have the time or inclination to keep the extraction column pristine, glass or stainless is a better choice.
Our local cost for borosilicate columns from the local scientific glass blower is only a buck an inch, plus five bucks to flare one end and close to an orifice on the other end.
As many of you have already no doubt noticed, there are also battle lines drawn around the use of plastic in a column. Some truth, but all plastics are not created equal.
HDPE, UHMW, XLPE, and PPE plastics are compatible with butane, but not PVC or CPVC. I strongly advise against using PVC for that reason.
When loading the material in the tube, we use a wooden dowel to keep it uniformly and firmly, but not tightly packed.
Before loading the tube, we wad up a coffee filter and stuff it in the injection port end, to diffuse the butane as it enters and so that no plant material blow back out into your extraction, should you need to release butane pressure in the middle of the process for any reason.
Having loaded the material in the column, which is essentially a tube with an open end and one closed except for the butane injection orifice, we need to close off the open end. Lots of ways to do that, but we use a double layer of coffee filter, plus a patch of 65/35% 160 threads to the inch (~80 micron) bed sheet, as blow out protection.
We hold those in place with a heavy rubber band, wrapped around enough times to hold the filters tightly in place. Because of the cold temperatures involved, these rubber bands may be used for more than one extraction, but not sequentially. I just toss them aside and sort through them later to see which ones might be suitable for a second extraction,
I also take a pair of scissors and trim away all extra filter material, so as to minimize the oil soaked up during the process. I find that if I am careful removing the filter after an extraction, that I can reuse it multiple times, so as to further minimize losses.
Skunk pharm use of a column is pretty unremarkable as compared to general practice. It is only our collection and processing techniques that divert from the norm. We simply support the column full pulverized plant material over a collection vessel and inject butane through it. The butane passes through the material in the column and dissolves the trichomes as it does so.
The cannabis oils in the trichomes remain dissolved in the butane as it passes out the bottom of the column into the collection dish, so when the butane subsequently evaporates off, it leaves the extracted cannabis oil behind.
As previously mentioned, we use a collection vessel for the butane cannabis oil mixture as it passes from the column and there is more than one choice. Because of space constraints, I will only cover two, which specifically are large surfaced open container like a 10” Pyrex pie dish using vacuum or conventional evaporation to minimize CBN conversion, and a smaller Bain Marie stainless container, which will be cooked off to decarboxylize and produce oral meds.
If discharging into a pie plate or a Bain Marie, we always place the receiving vessel in a hot water bath, to not only boil off the butane faster, but to also minimize water pickup from the humidity in the air. The heavier butane will keep the water laden atmosphere at bay until it is mostly boiled off.
When the stream of solvent running out of the bottom runs clear, we cease injecting butane and insert a basket ball pump needle into the injection hole and blow out any remaining liquid. A modified butane can nozzle adapter will adapt the needle to seal the hole.
After collecting and boiling off the butane with hot water, our process diverges, depending on our intended usage of the extract.
If it is to be only vaporized or smoked, we wash the butane extraction out of the 10” Pyrex pie dish with 190 proof ethanol and allow the mixture of alcohol and cannabis oil to evaporate off naturally, or vacuum it off. See attached pictures of simple glass jar vacuum reduction, as well as using a pressure cooker for a vacuum vessel, and attempts at vacuum distillation.
As most of ya’ll know, medications that will be subsequently smoked or vaporized, do not require up front decarboxylation, as it happens during the ingestion process.
If it is to be ingested orally, we simply wipe off the water from the original container and place it in a 240/250F hot oil bath in an electric fondue cooker with sensitive temperature controls. Some fry cookers also have sensitive enough temperature controls, but some have extremely wide dead bands in that range, as they are mostly produced to cook at around 375F.
Make sure that the container is sitting on something that suspends it up off the bottom of the oil pot. I throw four jar lids in the bottom of my electric fondue pot and use it for that purpose.
Never trust the numbers on the dial and use a good thermometer to set temperatures. We use either a mercury lab thermometer, or a digital one. Good temperature control is key to the process.
That means the device that you use to control the oil temperature must have a narrow dead band, so that the temperature control is stable.
I paid about $60 for a Quisinart fondue pot that was designed to heat sensitive sauces like chocolate and has excellent control throughout its temperature range. There are a couple of Revels in our group that are slightly larger and work well, plus cost only about $30, though they have a slightly larger dead band.
Some fry cookers have sensitive enough controls, but many deep fryers designed to primarily run at 375F, lack control sensitivity and have large dead bands at 250F.
When the pool of cannabis oil becomes almost quiescent, we remove it from the bath and continue with further processing. Studies suggest that 70% decarboxylation is the point of diminishing returns, so pool activity down to a few remaining small C02 bubbles is the signal that it is ready for further processing.
Either boil or distill off the alcohol until the liquid is reduced to a pool of oil and all but minor bubbles cease rising at the edges and then add at least ten volumes of alcohol and wash out the whole pot by swirling it and washing off any resin stuck to the sides.
Using a funnel, pour that liquid into a jar or bottle, seal it, and place that in the freezer.
I usually leave it at least overnight, but have pushed it to a couple hours. The liquid will lose its clarity and become slightly cloudy, primarily from plant waxes flocculating out.
Filter that liquid one more time, and you will have a bell clear extract, which is ready to reduce down one more time.
Place in a suitable container for return to the oil bath. Since you have much less material, a smaller one may be used.
At this point I put them in small stainless cups with their tare engraved on their sides or about a 250 ml beaker. The smaller container reduces the surface area that will be coated with oil when I cook it down the last time and knowing the cups tare weight allows me to take it directly from the oil bath and place it on a scale after simply wiping the exterior.
Since I know the tare, I then know the extracted weight, and exactly how much other ingredients to add. Once adding those ingredients, I place the cup back in the oil bath, where I stir it until well mixed and then decant into its final container.
Since the added ingredients include things that lower the cannabis oils viscosity, very little is left as a film in that container.
If I plan to use the oil as is, without adding any other ingredients, I extract it from the container using a pipette, so as to not leave a streak of material in the vessel. After I have extracted all that I can using a pipette, I wash the container and pipette out with hot alcohol, and save the wash for the next run.
Nothing is wasted or left behind.