BHO Extraction

Butane Honey Oil, or BHO, is the essential oil from the cannabis plant, extracted using n-Butane as a solvent.  If it is extracted from fresh material, it is a Concrete, and if from cured material, it is an Oleoresin.  A concrete or an oleoresin that has been winterized to remove the waxes, lipids, and fats, is known as an Absolute.

Butane Honey Oil extraction refers to the method used to extract the essential oils from cannabis, and there are multiple theories on the best way to accomplish this, as well as what material is best to use.

Perhaps 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. Butane produces one of the cleanest extractions, albeit typically at a lower yield than polar alcohol.

On average we have extracted about 18% oil by weight from bud, but as low as 5.7% absolute and as high as 25 absolute%.

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.

We’ve only tried a few processes here at the pharm, so I will cover only simple flow through columns, a thermos bottle, a pressurized system, and a closed loop one.

We currently use a closed loop system for BHO, and as I am covering that process on a separate thread named The Terpenator, where I will detail building our second generation automated system.

Prior to using our DIY closed loop system, we did our BHO extractions using single pass flow through packed columns, and experimented with a thermos and a simple pressurized system to soak at ambient temperature.  I will cover simple columns and thermos bottles separately, as the techniques are different and I need to make some more pictures for the latter.

Before we discuss how to extract the essential oils from cannabis, let us talk about the plant material to be used.  That immediately brings to mind the qualifying question, “What do you want to use it for?”

Oil that is to be vaporized, is normally treated differently than oil that is used orally or topically, because it doesn’t need to be decarboxylated.  For cannabis concentrates to be orally and topically active, it does require that the THCA and CBDA be converted to THC and CBD, by a heating or drying process.  I will cover that issue under a separate thread on Decarboxylation, so as to not clutter this post.

Terpenes:

Besides the cannabinoids, which are Di-Terpene alcohols and di-alcohols (diol), there are also other terpenes in cannabis essential oils, which add to its smell, flavor, and medicinal entourage effect.  Some of these terpenes are highly aromatic alcohols, phenols, ketones, aldehydes, ethers, and esters, which are aromatic because they freely give off molecules at even ambient temperatures.

Heating the plant material or the oil to decarboxylation temperatures will evaporate off most of these smaller aromatic Mono-Terpene and Sesqui-Terpene molecules, before the larger and heavier cannabis Di-Terpenes are affected.  Decarboxylated oil is smoother to the taste, but basically tastes like hash, with the floral undertones gone.

Gone also are the medicinal and entourage effects from those terpenes.  The price we pay for decarboxylation, so we shouldn’t decarboxylate casually, and should first consider the end use before picking the process.

One of our process  limitations, is that though non polar, n-butane has slight water solubility.  At 20C/68F, it is only 0.0325 percent by vol/vol, but not zero and is still  enough to pickup undesirable water solubles.  1 liter, or 1000 ml X 0.0325 = 32.5 ml of  water.

With water, comes water solubles, which includes chlorophyll and plant alkaloids, that detract from the taste, so the dance is to maintain the volatile terpenes, while studiously avoiding the water solubles.

Freezing the water is one method that works well, but it is important that the material be dry when it was frozen and that it is not exposed to high humidity while frozen, or ice will form over the trichomes, preventing their extraction.

Another method is to simply remove most of the water.  This will produce pristine extractions, but doesn’t preserve the terpenes.  If the material is to be decarboxylated anyway, that is of little concern, because we will lose them anyway.

We also have the issue of purging out the remaining butane, while preserving the terpenes.  Again, there are a number of ways to do that, but I will address only a few of the ways that have worked for us here.  Those are light heat, high heat, and thin film vacuum.

So, besides decarboxylation, what are some of the things to consider selecting a process and how should the plant material be prepared?

In our experience, for best flavor and taste, freshest material works best, whether it is fresh frozen material or dried.  Older cured material loses the nuances of the floral undertones and just tastes like hash.  That means that the degree of drying and curing is also critical, if your goal is to maintain maximum terpene content.

Oil from buds is tastier than oil from even sugar trim, because most of the terpenes are produced by the buds, and that is where they are the most plentiful.  Tasty is usually not a word used to describe oil from fan leaves or stems, though effective may be.

The absolutely most flavorful BHO extract to me personally and to the test panels thus far, is fresh picked buds, that are immediately frozen to tie up the water, and extracted while still frozen.  It produces an oil that abounds in whimsical flavors darting about and the word most often used to describe it by panel members, was the word “fresh.”

Next most flavorful, from a BHO standpoint, is material that has only been cured 5 to 7 days, and is at the small stem snap stage, where you might jar it if you were curing it to smoke.

Part of the formula is of course the degree and methods used to purge out the remaining butane.  While there are a number of ways to do that as well, I will address only a few of the ways that have worked for us here.  Those methods are low heat, high heat, and thin film vacuum.

Butane supply:

Lastly, selecting a suitable butane source is a key  step, in that all butane sources aren’t created equal.  n-Butane (normal butane) is a simple alkane, with four carbon atoms linked together in a row, with the remaining possible carbon bonding sites taken up by hydrogen atoms.

The simple alkanes all are gaseous at room temperature and atmospheric pressure.  They are removed from crude oil before it is further processed, by simple heating.  The simplest is Methane, which is only on carbon and four hydrogen atoms, followed by Ethane with two carbons, Propane with three, and Butane with the four.

Pentane is the next simple alkane, the first to be liquid at room temperature and the first to have zero water solubility.  From Pentane on, the simple alkanes are named from the Greek alphabet, and are Hexane, Heptane, Octane, etc, on through the light naphthas, oils, waxes, and asphalts.

The formula for all simple alkanes, is the number of carbon atoms times two, plus two, because each carbon atom has four possible bonding sites.  A mnemonic device for remembering the first four alkanes, which were named before the Greek system was applied, is Mary Eats Peanut Butter.

After removal from the crude oil, the gases are typically de-sulfurized using steam and a catalytic reactive bed, and fractionally distilled into the four basic gases.  As fractional distilling separates the gasses by specific gravity, the principal contaminants in n-Butane at that point, will be Iso-Butane, a branched molecule isomer of n-Butane, as well as n-Propane, and Cyclo-Propane, plus low levels of heavier, longer oleaginous alkane wax chains.

Neither of the butanes or propanes are particularly toxic at any sort of reasonable levels.  The following for instance is taken from a typical MSDS sheet for n-Butane.   The Rat LD-50 (50% dead) is 658000 mg/m3 4 hours.  That is breathing a 65.8% pure butane atmosphere and asphixiating.

MSDS info:

Section 11. Toxicological information for n-Butane; Diethyl; Freon 600; Liquefied petroleum gas; LPG; n-C4H10; Butanen; Butani; Methylethylmethane; UN 1011; UN 1075; A-17; Bu-Gas.

Specific effects

Carcinogenic effects No known significant effects or critical hazards.

Mutagenic effects No known significant effects or critical hazards.

Reproduction toxicity No known significant effects or critical hazards.

No specific information is available in our database regarding the other toxic effects of this material to humans.

Chronic effects on humans May cause damage to the following organs: central nervous system (CNS).

Other toxic effects onhumans

Toxicity data

Butane LC50 Inhalation Vapor

Rat 658000 mg/m3 4 hours

Product/ingredient name Result Species Dose Exposure

Products of degradation: carbon oxides (CO, CO2) and water.

Section 12. Ecological information

Products of degradation :

Environmental fate : Not available.

Environmental hazards : No known significant effects or critical hazards.

Toxicity to the environment : Not available.

Aquatic ecotoxicity

Not available.

The MSDS LD-50s on Iso-Butane, Propane, Cyclo-Propane, and oleaginous waxes are as follows:

n-Propane; Dimethylmethane; Freon 290; Liquefied petroleum gas; Lpg; Propylhydride; R 290; C3H8; UN 1075; UN 1978; A-108; Hydrocarbon propellant. LC50 Inhalation Gas:  Rat >800000 ppm 15 minutes

Cyclopropnane; Trimethylene; Trimethylene (cyclic); UN 1027;  No LD-50 established;

Iso-Butane; 2-methyl-; Trimethylmethane; 1,1-Dimethylethane; 2-Methylpropane; isoC4H10; i-Butane; Isobutane mixtures; UN 1075; UN 1969; R 600a; tert-Butane; A 31;Methylpropane; Propane, 2-methyl-isobutane LC50 Inhalation Vapor Rat 658000 mg/m3 4 hours

Oleaginous Waxes- Paraffin, no notable toxicity or LD-50 available

n-Butane is used for any number of things, so it is processing beyond this point, or sharing storage tanks with other contaminated sources that may create health concerns.  While n-Butane is non-toxic enough used as a food propellant, if it is to be used as a stove fuel, it will in most cases have an odorant added for leak detection, as n-Butane has only a very light sweet petroleum odor.

Ethyl Mercap is most often added for that purpose, and is the familiar rotten egg smell is detectable at the astonishing low concentration of under 3 parts per Billionth!   Hexane (Gasoline) by comparison, has an odor threshold of around 30 parts per millionth, or about 10,000 times more is required for us to smell mercaptoethanol.

The MSDS for Ethyl Mercaptan shows 4420 ppm/4 hour(s) inhalation-rat LC50; 682 mg/kg oral-rat LD50, with the target organs being the central nervous system.  Not super toxic, but tastes and smells of rotten eggs, so that point may be mute.

Butadiene may be added to stove fuel as well, and is of serious concern.  While the following typical MSDS example shows relative low toxicity, take a look at the carcinogenic effects.

LD50 Oral Rat 5480 mg/kg -LC50 Inhalation Vapor Rat 285 g/m3 4 hours

LC50 Inhalation Vapor Rat 285000 mg/m3 4 hours

LC50 Inhalation Gas. Rat 128000 ppm 4 hours

Mutagenic effects No known significant effects or critical hazards.

Reproduction toxicity No known significant effects or critical hazards.

No specific information is available in our database regarding the other toxic effects of

this material to humans.

CARCINOGENIC EFFECTS: Classified 1 (Proven for humans.) by IARC, 1 (Known to

be human carcinogens.) by NTP, + (Proven.) by NIOSH, 1 (Proven for humans.) by

European Union. Classified A2 (Suspected for humans.) by  ACGIH.

MUTAGENIC EFFECTS:  Classified 2 by European Union.

May cause damage to the following organs: the reproductive system, mucous membranes, upper respiratory tract, skin, eyes, central nervous system (CNS).

n-Butane may also be further refined to increase its purity, or to make it suitable for use in butane lighters.  R-600 Refrigerant and Instrument grade n-Butane are examples of higher purity n-Butane suitable for extractions, and are distributed by suppliers like Matheson and Airgas.

Lighter Butane:

As those sources are expensive and not usually available to non commercial customers, in support of federal guidelines listing it as a controlled substance used in the manufacture of illegal drugs, most folks use butane made for butane lighters.

Each manufacturers blend is slightly different, with n-Propane usually added as a propellant, because below the freezing temperature of water, butane is a liquid instead of a gas.

They also further refine the n-Butane to remove more of the low level oleaginous waxes, which clog  the small orifices in expensive butane lighters.  This is often shown on lighter butane cans as a number followed by an X.  IE:  5X.

The common name for Oleaginous Waxes from petroleum, is Paraffin, which is non-toxic enough to have no known LD-50 data and be used to seal jelly jars, so they are of low concern when extracting.

Here Madison Avenue has gotten a foot hold, and even 7X butane is available for even more money, though there is no advantage over a good 4X for the purpose of extraction.

One refiner has started labeling the brand names that they produce, Near Zero Impurities, guaranteeing under 50ppm impurities.  An independent test showed that they in fact are under 50 ppm, and even under the 15ppm testing cutoff, as were competitors brands not touting near zero impurities.

If using lighter butane, the safest course is to use tried and proven brands, but if forced to improvise, first obtain a MSDS sheet from that specific manufacturer, showing the contents.  Reject any containing mercaps or Butadiene.

Ingredients less than 1% need not be shown on the MSDS sheet, unless they present a health risk at the levels present, so they are not all inclusive, but a good place to start.

If the MSDS looks OK, spray a five second burst on a mirror or clean glass pane and let it completely evaporate.  Check for residue.  Smell it for mercaps; you can’t miss them.

Each brand extracts slightly differently, because the mixes are slightly different.  Adding propane for instance, increases water solubility and the propensity to pick up water solubles.

Here are some brands that we’ve tried and work well, as well as being tired and proven brands by others.  This list is by no means inclusive:

Colibri

King

Lucienne

Newport

Vector

Safety:

Butane is highly flammable, so let us next talk about safety. First and foremost, always perform the extraction outside in a well ventilated area.  Have a fire extinguisher handy, as well as a blanket to roll up in, should the unthinkable happen.

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.

Material Prep:

Material prep will of course depend on the application, so lets cover that subject generally.

Fresh buds should be dry of standing water and cut into small pieces, before being stuffed into a column or thermos and placed in a -32C/0F freezer for 48 hours to solidify.  Fresh frozen buds produce the most aromatic extraction.

Second best for for maximum terpene retention are buds ground up after 5 to 7 days hanging, or as soon as the small stems break freely.  They should be jarred immediately to retain freshness and run as soon as possible to prevent molding.

When extracting dried buds for vaporization, or bragging rights, the material is broken up just loosely enough to extract, but not enough to expose excessive broken cell boundaries.  That can be done by hand, or with a nugget buster.  Here is an example of a nug buster design that I scored off Roll It Up forum, but alas I can’t remember the author:  The wire cloth can be obtained from Howard Wire at http://howardwire.com/square_mesh.html

Nug buster-1-1

Nug buster base-1-1

Buds for decarboxylation and most pristine appearance, should be placed on a coffee sheet and baked in a 94C/200F oven until just frangible, when rolled between the finger and thumb.  They can then be ground or scrubbed through a pasta strainer to remove the sticks and stems.  They should be jarred after grinding, to keep moisture pickup low.

The material shouldn’t be bone dry as it will become too frangible, nor should a coffee grinder be used, because of the fines that it produces, that have to be subsequently removed.

We also dry our trim and leaves until frangible as above and scrub ti through a pasta strainer, using a leather gloved hand and firm pressure, so as to minimize the amount of fine particles generated.

So now that we have covered some of the basics, lets move on to the different processes:

Simple Flow Through Column:

One of the simplest methods of extracting using butane, is a packed column.  A column is a long narrow containment that allows a solvent to be passed though it using either gravity or pressure. The column is packed with plant material to be extracted and the essential oils are dissolved by the butane and carried out the filter in the bottom of the column, into a collection device.

Column materials:

Columns may be made from any number of different materials, but not all are suitable for butane service.  http://www.coleparmer.com/Chemical-Resistance is an excellent site to check material compatibility with the various solvents.  You do however have to read between the lines, and for medical use, stick with those materials listed as excellent.

Using those guidelines, a quick check reveals that Poly Vinyl Chloride (PVC), Acrylonitrile Butadiene Styrene (ABS), Low Density Poly Ethylene (LDPE),  for instance, are not suitable, even though listed as good to fair, because the butane leaches out the constitutes, so they will end up in the meds.

They list copper as fair, not because the butane attacks it, but because of sulfur compounds and water that may be present in the butane, which form sulfuric acid and attacks the copper.  Dry low sulfur butane doesn’t present the same issues, but copper columns have to be kept meticulously clean of oxides, as for instance, welding copper without adequate respiratory protection, produces a medical condition known as fume fever.  If you do not have the time or inclination to keep the extraction column pristine, glass or stainless is a better choice.

Poly Propylene (PP), Poly Vinylidene  Fluoride (PVDF), Polytetrafluorethylene (PTFE=Teflon), are listed as excellent, and High Density Poly Ethylene (HDPE), Ultra High Molecular Weight Poly Ethylene (UHMW), or Cross Linked Poly Ethylene (XLPE) may be, but are not listed.

Glass and borosilicate (Pyrex) work well, as does 300 series stainless steel.  Neither are dirt cheap, but 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.  1″ Stainless schedule 10 pipe was only $6.20 a foot, last time I checked, but prices vary considerably, so you should check local sources for pricing.

I don’t recommend single pass columns with a larger ID than 1″, as extraction efficiency drops rapidly above that size.  Primarily because the material near the injection end is inadequately wetted, and because the larger the column, the easier it is for the butane to just find an easy route through, and continue to follow it.

The absolutely cheapest stainless column that I’ve found is one made from a stainless turkey baster from Bed,Bath, and Beyond for $7.99.  Throw away the bulb and pull the press fitted needle out of the threaded adaptor, and you are good to go.

I’ve made a number out of copper, usually with a union near the injection end, so that it could be easily opened and cleaned.  I also made a copper one with a can holder at the top, using a contractors size caulking gun, and my first experiments with pressurized butane extraction, were in a copper test sled.

In the latter case, we also added vibration and as we try to use free donated material where at all possible, I draw your attention to the gold plated personal vibrator used for that action and give thanks to the donor, whom wishes to remain anonymous.

A stainless column can be made by screwing a cap on one end and screw radiator clamping a double coffee filter over the other end.  Drill a 1/8″ hole in the cap for the butane nozzle, and after thoroughly cleaning the insides by washing out with alcohol and boiling in hot soapy water, it is ready to go.

You can also stick a one hole Neoprene cork in the top of the column, instead of using a cap.  It works well enough, though more sensitive to blowouts.

We have our borosilicate columns made and some development was required to stop breaking them in cold wet weather.  What was required to stop spalling off conchoidal divots from the injection port in frigid weather, was to make the closed end a smooth even radius of uniform thickness, so that stresses from uneven expansion and contraction were not an issue.  You also need to insure that the column is annealed after forming, to relieve all residual stresses.

We add a flare to the ends of our borosilicate columns, to make filter retention easier, so as to reduce blowouts.

A blowout, is where the filter at the end of the column ruptures and blows the column contents into your collection vessel, or the filter blows off entirely, doing the same thing, or when using a cork in the top, it blows out during injection.

You can guard against filter rupture, by backing the coffee filter with stainless mesh, or cloth.

Preventing a blow off gets trickier with glass tubes, in that you can’t just crank down harder on the radiator clamp, without breaking the glass.  Alternatives that work better with glass, are twine wraps, zip locks, or rubber bands.  We mostly use rubber bands, and stretch them tight.

Column Loading:

When loading the material in the tube, we use a wooden dowel to keep it uniformly and firmly, but not tightly packed.  A dowel close to the ID of your column will make even packing easier.

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 our extraction, should for any reason we need to release butane pressure in the middle of the process.

We cut the top out of a water bottle to use as a funnel, and pack the material as we load it, stopping about every foot to compact.  When the column is full of plant material, we double a coffee filter over the end, and then cover that with a cloth patch, securing both with multiple tight wraps of a heavy weight rubber band.

We also scissor 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.  We also wash out our filters in alcohol, to recover any essential oils soaked into them.

Skunk pharm use of a column is common general practice, though our collection and processing techniques deviate from the norm. We simply support the column full of pulverized plant material over a collection vessel and inject butane through the top port in the column, and let gravity carry it through the column.

As the butane passes through the material in the column, it dissolves the trichomes, and conveys them out the end of the column, into the collection vessel.  The butane subsequently evaporates off, it leaves the extracted cannabis oil behind.

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.

Examination with a microscope will tell you when the trichomes have been dissolved away, and looks like wet hairs lying down, with the capitate heads missing.  Our average yield at this point was around 17 to 18% by weight, but we’ve yielded up to 21.6% by dumping the column, repacking it, and making a second run.

This second run will be less heady, and of lower viscosity, with more sedative properties, so we keep it separate from the first.

Collection vessels:

How we are going to use the oil, to a large degree dictates how we collect it, so lets look at some of the methods we’ve found effective.

Pyrex Pie Plate:

The first that I tried, was collecting in a 10″ Pyrex pie plate, sitting in a larger Pyrex dish full of hot tap water.  That works well and the key is the hot water that it sits in, in at least this neck of the Pacific NW rain forest, where we often have high humidity.  If we don’t set it in hot water, ice forms at the edge of the evaporation pool, adding considerable water to the mixture.

The hot water also rapidly boils off the butane, until all of it visibly gone, although some remains un-purged and in solution with the oil.  Techniques for purging the remaining material vary, so we will cover those steps as a separate issue.

This technique is suitable for any process, with certain precautions and subsequent processing.

Stainless Bain Marie:

Even better in this land of the midnight rain, is a deep stainless bain marie container, sitting in a hot water bath.  The deep vessel fills with butane fumes, which floats away the atmosphere, so that no moisture laden atmosphere is anywhere near the evaporation line of the butane.  That is how we processed most of our oil, when using single pass columns.

The real advantages to using this type of collection, are that it can be wiped dry on the outside and the pot set directly into a hot oil pot for a rapid purge and decarboxylation, followed by formulation in the same stainless vessel, so that nothing is lost to films left behind in transfer pots.  We have the tare marked on each of them, so that we can weigh the material while still in that pot, to establish yield, and the quantities for the rest of the ingredients.

This system works well for decarboxylated and formulated meds, but presents a challenge to remove the oil afterwards, if you are not, and has less surface area for evaporation if you aren’t planning to hot purge or wash it out with alcohol and do thin film vacuum purging.  Absolutely the best method we’ve found overall, subject to the above limitations.

Purging:

Butane is relatively easy to purge from cannabis oleoresins or concretes, as it has a boiling point of around -.5C/31.5F, or right about the freezing point of water.  Given enough time just sitting around, it will purge below our 5000 ppm smell sensory threshold, and even our far more acute sense of taste, either of which is a small percentage of the 658, 000 ppm, that the MSDS LD-50 tells us it took to asphyxiate 50% of the test rats in 4 hours.

We can speed up that purge, by using a dish with a large surface area, relative to the depth of the pool of oil.  Usually small extractions, so as to keep the pool depth thin, are the easiest to purge.

Typically, the thin film is scrapped and stirred periodically, to speed up the process, and a flame may periodically be lightly run over the surface, to warm it and determine if the bubbles exiting are butane and terpenes, or CO2.  Some care needed here, as THC, CBD, and CBN are di-terpene alcohols, and are flammable themselves, as are the other terpenes present.

Air movement over the pool speeds up evaporation, by whisking away the saturated boundary layer and providing the extra energy for the molecules of butane to escape the surface of the oil, as it is ricocheting about in the pool.  Care must be exercised here, as any dust or lint in the air will end up in the oil, so usually a cheese cloth or similar porous cover is placed over it, before blowing over the top with a fan.

We can also speed it up with the application of heat.  Any heat will speed up the evaporation, and one line of thought is to keep the heat low and around 60C/140F, using a hot pad after the hot water bath and scraping and popping any bubbles with a razor blade.  A typical purge might take an hour and provides maximum terpene retention.

When adding bottom heat, you can also add a loose fitting lid, which will speed up the purging and keep out lint and dust.

For a faster purge, the temperature can be raised to above the melting point of the cannabis essential oils, or around 82C/180F, to give the butane molecules maximum mobility.

Instead of heat, vacuum may be applied to speed up the purge process.  That is the process that we use when we wish to maintain the cannabinoids in their carboxylic acid forms.

In thin film vacuum purging, we place about an 3/16″ of the oil in a 6″ Pyrex Petri dish, and place that in a vacuum chamber, which also contains a hot plate.  That allows us to manipulate both the temperature and atmospheric pressure, so that we can achieve boiling at very low, or even ambient temperatures.

While we use 180F to vacuum purge a raw oleoresin, adding heat isn’t necessary when thin film vacuum purging raw oleoresins redissolved in ethanol.  The alcohol will boil away under 28.5″Hg at ambient temperatures, as will the water that is left behind, even without adding any heat.

For our oral and topical meds, we exclusively used the bain marie collection vessel, and simply wiped the water off the outside, following the hot water purge, and set it in an electric fondue pot full of hot 121C/250F Canola oil.

The residual butane will boil off first, exiting in larger, multi sized bubbles, followed by the smaller equally sized CO2 bubbles from decarboxylation.

Depending on the use, we remove it from the hot oil when the bubble activity suddenly slacks dramatically off, indicating the 70% peak of the decarboxylation curve, or when it becomes quiescent, if we are looking for maximum sedative effect.

Hot oil Pots:

We use electric fondue pots for decarboxylation and I prefer the Quisinart, for their sensitive controls and narrow dead band.  We also have a couple of Rivals, which work well too, but whose controls aren’t as sensitive.

Some fry cookers may have sensitive enough controls, but most are designed to primarily run at 375F, and lack control sensitivity, as well as have a large dead band at 250F.

It is important to make sure that the container is sitting on something that suspends it up off the bottom of the oil pot, to eliminate direct transfer hotspots. We keep several jar lid rings in the bottom of our electric fondue pots for that purpose.

We never trust any controls however, and use a good mercury lab thermometer, a digital, or an infra red optical pyrometer to establish and control temperatures.

Thermos extraction:

Thermos extraction is a technique allowing an extended soak period at atmospheric pressure.  At sea level, n-Butane boils at approximately -0.5C/31.5F, so unless the local ambient temperature happens to be under that temperature, the butane will warm up enough to return to its gaseous state.

In thermos extraction, the prepared material is loaded into a stainless steel thermos bottle and frozen before having pre-chilled butane added.  The thermos acts as a Dewar to keep the butane temperature low enough to keep it in its liquid state.

Dropping the temperature will of course also slow down the extraction rate, so the resident soak time must be increased to compensate.

An advantage of keeping the temperatures low, is that it allows you to run fresher material, as the water will be tied up in the form of ice.

Butane has the very slight water solubility of 0.0325 vol/vol, or about 32 milliliters per liter.  That means if there is any water available, some of it will come along and bring with it undesirable water solubles, such as chlorophyll.

Tying the water up as ice, allows a longer soak resident time, without picking up those water solubles.  Operating at 50F outside temperatures locally, an optical pyrometer showed the butane in the thermos to hover around +8.7F, with mild bubbling action and minimal loss of liquid.

Because of the low operating temperature, you can run either fresh frozen or dried material equally well and can therefore control a wide range of flavors, by simply controlling the pre extraction state of drying, and evaporation of aromatic terpenes.

A fully cured material will produce hashy tasting oil, and fresh material will produce floral oils, and the rest of the flavors will be in between.  The flavors besides cannabinoids, are the lighter mono and sesquiterpenes, which are the aromatic alcohols, phenols, ketones, aldehides, and esters.

Equipment required for this process are minimal.  I scored a gorgeous little stainless steel thermos at the local Goodwill for $4.99 and my only alteration was to drill three holes in the cap.  One to fit a lighter butane can nozzle, and a couple to allow venting during injection.  I tossed the inner lid, as the gasket was unsuitable for butane.

After soaking one hour, we pour the butane through a strainer suspended over a bain marie catch vessel, but we also subsequently winterize, so if you aren’t going to, you can rubber band a coffee filter over the opening and dump through that.

A second soak in chilled butane may be used to extract any remaining essential oils.  Jump, one of the developers of the process, reports using a 30 minute first soak, and a 2 hour second soak, with pictures showing pristine quality from both extractions.

Once in the catch vessel, the extract can be purged any number of different ways, like any other BHO extraction.

Notice in this case, we broke up the buds and removed the stems in a harvest box, which we subsequently harvested the kif out of for our pipe while standing around.

 

GW

682 responses to this post.

  1. Posted by matt on December 18, 2014 at 8:18 AM

    why is my BHO drying out in the vac purge and looking like a peanut butter cookie

    Reply

  2. Posted by Cedric on December 13, 2014 at 2:57 PM

    Hey there! How do you test for Butane residues in your final BHO extraction? Is there an easy and kinda accurate way to test for it? And last question: Can you purge with a simple vacuum system?
    Best, C

    Reply

  3. Posted by Matthew Petela on December 2, 2014 at 4:46 PM

    Can I use raw tricombs to make bho?

    Reply

  4. Posted by Lmo on November 20, 2014 at 7:18 PM

    Hey there, I’m considering trying out the thermos method, but using cold water hash as my material. There are just a few points I wanted clarification on. First, in regards to the thermos you found at goodwill, you say you tossed the inner lid as it wasn’t suitable to come in contact with butane. What did you replace it with? Second, I pitched this idea to a friend who does pass thru open blasting and he warned of saturating the butane to the point it won’t absorb any more oil. I know to remedy this problem I can simply repeat the soak with the same material and new gas to get what’s left, but could you point me in the direction of a good starting point as to what how big of a thermos I’ll need/how many cans I’ll have to use/how long of soaks and how many it will take if I want to extract from roughly 3oz bubble hash? I’ll be using just about every grade/bag I get with the possible exception of the first after workbag (160u) if that info is pertinent. I’m looking at a thermos brand 32oz bottle that looks very much like the one pictured in your explanation of the process as my vessel for the job. Do you think 32oz is a sufficient volume to be able to run the 3oz bubble without having to soak more than twice, or should I go for something bigger?

    The other thing I am pondering and would appreciate some help on, is dewaxing the resulting solution IN the butane (not winterizing with ethanol). I was wondering if to do this I can use the following method- dump through wire strainer to bain marie post soak as u do, but have that bain marie sitting in a larger one with dry ice, allow waxes to precipitate, strain through buchner funnel with filter paper, reduce and vacuum purge from there?
    I’d greatly appreciate on what if any of this sounds like it could work, or what could be altered about the process

    thanks

    Reply

  5. Posted by rawb on November 20, 2014 at 10:51 AM

    when you de-wax do you do anything with the wax? I was wondering if it was good for anything.

    Reply

  6. […] BHO Extraction | Skunk Pharm Research LLC – Butane Honey Oil, or BHO, is the essential oil from the cannabis plant, extracted using n-Butane as a solvent. If it is extracted from fresh material, it is a …… […]

    Reply

  7. […] are a number of extraction techniques for hash oil; and the dangerous one in question is the BHO extraction method. Essentially, you use butane oil to help separate the hash oil; and because butane has a low […]

    Reply

  8. Posted by Jason on November 6, 2014 at 1:39 PM

    What’s a good butane to use? I was thinking about getting lucienne but I saw mystery oil page, I also saw pure tane and its saw it only n butane, would like to get your take on pure tane

    Reply

    • pure tane is just advertizing gimmick my dude, used both lucienne and pure; i’ve gone back to lucienne. we’ve distilled pure and still pulled mystery oil out of it even though they claim it’s not there. important thing to remember about mystery oil is that it does not evap with heat so in the end you’re not even smoking it.

      Reply

  9. Thank you so much for the great writing! I am a lifelong electronics fella with some helpful ideas of providing exact heating for your applications, and am getting into the cannaIndustry. Please drop a note if your interested in the free ideas your electronics guru can put together, or I can for you to try.
    Keep up the great work!!!

    Reply

  10. Posted by snowoil on October 19, 2014 at 9:54 AM

    This is great info here!! One question GW. The decarboxylation process(when the bubbles are all the same size), do I stop purging here or continue? I have noticed this before but thought they were butane bubbles.
    Thanks for your help!

    Reply

  11. Posted by Nick on October 18, 2014 at 2:59 AM

    Hi I was wondering if you could give me a step by step on how to get the oil from my saved up coffee filters.

    Reply

    • Posted by snowoil on October 19, 2014 at 10:00 AM

      I would assume you just soak them in a glass of alcohol, remove filter when its clean then boil it off. Be very careful with alcohol!!!!! When I use alcohol I prefer to let it evaporate naturally.

      Reply

  12. My spouse and I stumbled over here coming from a different
    web page and thought I might check things out.
    I like what I see so now i’m following you. Look forward to
    exploring your web page repeatedly.

    Reply

  13. Posted by ERIC on September 28, 2014 at 2:15 PM

    HI I sell Used $5,000 HIGH VOLUME VACUUM PUMPS FOR $500.00
    The Pumps are a ALCATEL 2021I
    They are in GOOD USED SHAPE 14 CFM
    CONTACT ME at STYLEENTERPRISES@YAHOO.COM

    Reply

  14. Your calculation for water solubility of butane seems faulty or possibly unclear to me. There is a percentage, which i dont believe you calculated right.

    Reply

  15. Posted by Sam on August 27, 2014 at 7:23 PM

    Is there any benefit or draw backs to blasting bho directly into 190 proof at room temp, then winterizing at sub 0 for 24-48hrs, filtering, heat evap, then thin film vac purge till done? Any thoughts on this process

    Reply

    • Posted by runcmt on September 9, 2014 at 9:22 AM

      One draw back is you can blow yourself up!

      Reply

      • If you can manage to blow yourself up through the extremely simple and safe butane extraction of MJ….sorry but you deserve to be dead. Nothing personal, we just do not want those dumb genes being passed on.

        Reply

  16. Posted by Chewy on August 16, 2014 at 8:51 PM

    Whats up folks, Could you enlighten me on “Live Resin” process for BHO? i am semi-savvy about the process, but a breakdown would be rad. Thanks

    Reply

  17. Posted by jason on July 30, 2014 at 5:07 PM

    I Just ordered the HeatVac XL heated Vacuum purge kit. First time user for this product, I’m hoping its nice. Long story short, I’m using all high grade buds that have been in the freezer for 24 to 48 hours. I’m blasting through a two foot glass extraction tube using about two ounces of product along with Stok butane. Ok, So here’s my questions, the kit comes with a 5cfm 2 stage vacuum pump. With the amount of product I’m using, HOW MANY CANS OF BUTANE SHOULD I USE? HOW LONG DO I PURGE FOR? IS THERE ANY SPECIFIC SIGNS I SHOULD BE LOOKING FOR? And Last but not least, HOW DO I KNOW WHEN ALL THE BUTANE IS GONE? Someone PLEASE help me out? MASSIVE LOvE.
    ~SMiLES

    Reply

    • Posted by pete on August 13, 2014 at 7:30 AM

      I heard 1 can to an oz for nugg runs. For trim i would think half a can. You can also do a dry ice hash run first, if you have bubble bags. After you can run just that through your extractor and use half the tane.

      Reply

    • Posted by BluJay on August 14, 2014 at 11:44 PM

      If you freeze the butane you will find you need less, typically 1/2-1 can per oz. Purging time will vary; you will have to purge until it makes no sight/sound when dabbed and of a solid consistency.

      Reply

    • Posted by CC on August 28, 2014 at 3:15 PM

      Hey, first of all I think 3-4 cans of butane should work fine, when the butane and oil is coming out of the tube look for it to run clear and not be sticky if you get some on your hand. When doing the first purge you’re looking for the bubbles to stop forming after putting your dish or whatever you use in the warm water, when the bubbles are small and there is little to no reaction to the water the first purge is done. The vac chamber purge varies depending on who you talk to as far as length of time. Basically what you are looking for is for the oil to not puff up when in the chamber, and all the large (butane) bubbles to be gone. I like a clean product so I prefer to purge it in smaller batches for about 3 1/2 to 4 hours. If you still can’t tell try some out and if it sparks there’s still butane in it.

      Reply

  18. Posted by Howelly on July 5, 2014 at 12:53 PM

    I’m a total novice with no experience in this field at all and would like to prepare for an extraction in a couple of weeks following a harvest.
    I would like to hear peoples views on “simple flow” vs “thermos” method. Both of these method looks straight forward and the materials are all to hand and easy enough to prepare for a beginner like me.
    I’m looking to make an oil with less of the sleepiness and preferably pre-decarboxylated for easy dosing.

    Reply

  19. […] Hash Oil, has been a controversial topic in the news. While it is certainly possible to use butane responsibly to produce a safe and solvent-free extract, that's not always what happens — and at this point, the responsible thing for us to do is to […]

    Reply

  20. […] butane extraction safety breakdown: This list will be updated as seen appropriate but of course read as much as you can and do yourself a favor and read Skunk Pharm’s Butane Safety Article […]

    Reply

  21. […] PumpRite chart, PVC is given a rating of A. In general, plastics should be avoided altogether–Skunk Pharm states in their BHO article, “a quick check reveals that Poly Vinyl Chloride (PVC), Acrylonitrile Butadiene Styrene […]

    Reply

  22. […] Thought this article might be useful to you as you draw near to giving this a shot. BHO Extraction | Skunk Pharm Research LLC […]

    Reply

  23. Hey GW,
    What about butanol ? It’s allot safer! and would it be possible winterize in
    that solution?

    Reply

  24. Posted by Waleed on March 1, 2014 at 1:28 PM

    Hey GW, i’ve been trying to find a good amount on information on thermos extractions ive been reading everywhere but no one seems to give a good detailed explanation of soak times, i currently associate with a couple dispensaries and ive been trying to increase yields i have been using open tube for 3 years and would like to switch to thermos before i get my closed tube. My question is how long can you soak i understand you have said that your friend does 30 min and 2 hour soaks with both being pristine extractions. which is great but im curious if you do soak for lets say 4-6 hours could you still get pristine quality and yield more? (also would you i be pulling more fats cause of the soak?). I am using grade a trim after about 5 days of drying(small stem snap). using open tube i get yellow, amber, light colored high quality extracts in general. not trying to gloat as i have copied the tec from others(including yourself) and the growers have done everything for me i just would like to know if that color would darken for longer soak times… I also am curious if you have heard of dewaxing it is like winterization but using butane i havnt read anything on here about it and would like to share the information with you if you havnt heard of it(i was assuming you are aware but did not post it on here cause it is a lot more dangerous.) i dont get why people like adding a second solvent when u can remove the fats with the solvent you are using to extract before the butane evaporates, much easier imo and you dont have to use another solvent that boils at a much higher temp.

    Reply

  25. Posted by John nichols on March 1, 2014 at 6:47 AM

    Is there a way to (clean) the bho so that it has a nice golden color instead of a pine tar look?
    John

    Reply

  26. Posted by joe rodriguez on February 28, 2014 at 2:06 PM

    Couldnt you blow into a parchment paper on silicone pad under bubby hot water til evaporation, vac for a few, flatten to square, then vac for 12-14hours? on 81-84 degrees on the hot plate, decarbing and purging all the terpenes out? But how do you know what heat for wax and shatter?

    Reply

  27. Textures of your extracts:?
    do all your vaporizing extracts finish in a shatter or hard type state?

    Does Trim vs Flowers finish different? Or is all truly purged oil hard?

    Stretch snap consistency. Familiar with it? Is this a slightly un purged product? Or a “damp” un cured product?

    Do you find fresh flowers are harder to purge then say older trim? or is it it’s water content that makes it seem softer longer?

    How long of a low temp purge (120f) is too long? and still never get to shatter?

    I’ve read it that slightly tacky extracts may have decarboxolized? but isn’t your photo of the decarbed oil described as “flint” hard?

    I’m baffled by the variation I get in a seemingly identical process.

    Reply

  28. Posted by patrick on February 28, 2014 at 2:34 AM

    Helo, I just have a couple questions. i have been keaping up with your page for some time now becuase the whole prosses facinats me and of cours i love wax. but i just started to do runs and so far it hasent been pritty the wax has been awsome though its a perfect amber goo. but back to my questions, iv ran two times with half Ounce and got pretty good resalts with both those runs lost some wax in the containers but not bad about two grams with blow through turky baster and in the small thermos run i got 3 grams but when i scaled up and ran 2 ounces through the blow through i only got 5 maby 6 grams do you think that becouse i ran it 3 seprat times onto the same pyrx and had hot water under it while i did all three runs i ran each tube with about 3/4 can butan till it ran clear each tube holds a littbit less than an once also i brake up the bud fine also in all the containers i notice alot of kief after run is this normal to and im realy trying to perfect this so i dont lose more

    Reply

  29. Hey gray..

    Running a closed loop system, an active one. Coming across residue.. Just trying to distill my CP n-tane. A tire smelling amber colored shit. I am running an appion with this system. Is it possible to pull this residue from the appion? Is my n tane from airgas just dirty? I’ve distilled it 3 times with the same residue. Now I’m runnig a passive recovery to see if it’s still there. Thoughts, opinions?

    Reply

  30. Posted by Joe C on February 24, 2014 at 2:56 AM

    Hi Skunk, Ive read in a few places before stumbling on your awesome site that dehydrating or putting bud in the oven before is better for BHO extraction… i plan to winterize but not decarboxylate as the end product will be vaporized… What are your thoughts on the drying pre extraction? & any other suggestions greatly apprecited !

    Reply

  31. Posted by C4h10 on February 20, 2014 at 5:34 PM

    Hello again GW I’ve been noticing that compared to others peoples concentrates mine seems to have less taste. I purge at about 105 for 12-24 hours (depending on size of the slab) and flip it once or twice during that time. I’m at just over 3000ft so my vac chamber only hits about -28. The bud I use is dry but not so dry that it turns to powder when broken up. I always hear that going low and slow makes for the best stuff but I’m almost wondering if the long purge is killing the taste? Would it be more affective to go higher temp for a shorter period of time? I don’t think the buds are too dry but maybe. The concentrate looks amazing (see for your self here http://statigr.am/p/653741789863261970_331412092 ) but I’m still not happy with the taste. Thanks for your time

    Reply

  32. Posted by Alex on February 20, 2014 at 8:50 AM

    Plan on making my 1st run this weekend. I’ve read the forum from top to bottom but I still have questions, or maybe just need reassurance! I bought a Glass essential extractor 15-30 grams and plan on just making some for personal enjoyment. I live in FL so heat and humidity are an issue. I will outline the method I plan on employing along with any questions I have. Any and all feedback would be greatly approcated.

    1) I have high quality flowers and I plan on breaking these up slightly, but not grinding them up like I would for regular consumption. These have been fully cured and I keep them vacumn packed in mason jars. Once packed in the extraction tube should I freeze before blasting?
    2) I plan on blasting directly into a pyrex dish in a hot water bath until the butane has bubbled off sufficiently.
    3) I then plan on transferring the extract to a Oil Slick DUO pad and heating on a hot plate or heating pad to diffuse the remaingin butane as I do not have a vacumn chamber. I want to use the final product in my vap. My question here is, what temp do I want to stay below in order to maximize the potency/effect? From what I gather it is 130-140 , is this accurate? Is this processed finished once the bubbles cease to develop or become less frequent? Is there adding vlaue to letting this air cure after the heated purge?
    Besides this basic outline I do have a couple of additional questions. Why do some of the videos that i’ve watched that detail this process end up with glass while others end up with a dryer more powdery sustbnace that i guess people call budder? Also I have a food saver and was thining of rigging up a vacumn of sorts using a mason jar and heat. Do you see any value in this? Finally, if I plan on vapping do I need to winterize or is this more of a personal preference?

    Sorry for the long post I juist dont want to ruin high quality flowers that took me a while to save up for!… Again any feedback is greatly appreciated!!!

    Reply

  33. http://tiny.cc/d49kbx–Its a polypropylene cap with a silicone seal that screws onto mason jars, wide or regular, spill proof. works AWESOME for mason soaks, self filters to a decent degree for winterizers, use mesh if just purging. That link goes to the ebay sellers page for the caps. Stay safe

    Reply

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  35. Posted by ThirstyMind on February 12, 2014 at 10:09 PM

    What are the best practices, safety-wise, for thermos extractions?

    I’m thinking…

    – Since the system (thermos and butane) have been chilled, the butane enters the thermos as a liquid. This improves safety, right? It’s less likely to explode during this step?

    – Static electricity is a big concern, where I live. I’m getting shocked all over the house right now. There are two critical moments I can think of: (1) when the butane can comes near the thermos during injection, and (2) after the soak, when pouring the butane from a metal thermos to a metal strainer/bain marie. How do I mitigate these concerns?

    – The most dangerous time seems to be when emptying the thermos after the soak, because the butane starts to boil off quickly. I will have a fan pointed at it (pushing not pulling). Anything else I should do, besides keep my distance until it’s done?

    – How far should I be from possible ignition sources, outdoors? My back yard is pretty big, but not acres big. I know butane expands like 230:1, and is explosive at very low percentage, so is my entire big back yard made explosive by a 300ml can? For how long?

    Trying not to go all OCD on this, but I really don’t want to blow up…

    Reply

  36. Posted by Elbretto on February 12, 2014 at 12:54 AM

    Hello there, I have some questions regarding process in timing and temps.
    I have had trouble in the past in getting all the butane out and need help with purging. Using the double Pyrex boiler method blasting from a glass column, what is the best temperature to have the water at on initial blast? After the tane runs clear, I stop. But sometimes I blast again and see some green come out. What’s the best way to ensure you are extracting the most oil possible? While letting the solution sit and purge, is it best to increase temp (if so, how high) or to let it stay the same? I do realize that time is all subjective, but when is it best to scrape or should I be agitating it frequently? I usually let it purge for a good two hours before collecting it and placing it on a slick pad, and purging again. Again, I want the butane all out, and unfortunately I can’t afford a vacuum, so any more advice on purging techniques on how to make the best quality using hot water, toaster oven, lamp, etc will greatly be appreciated.

    Reply

  37. Posted by willbur on February 10, 2014 at 9:03 PM

    so, this isn’t related to bho but I was curios if water extraction takes out any plant waxes? just a thought I had thinking about all of those things being “water soluable.”

    Reply

  38. Amazing things here. I am very satisfied to look your post.

    Thank you so much and I am having a look ahead to contact you.
    Will you please drop me a e-mail?

    Reply

  39. […] don't listen to your friend, here are some good links Guide to BHO http://skunkpharmresearch.com/bho-extraction/ Guide To QWET (a way better version of what your friend suggested) […]

    Reply

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