Concentrated Cannabis, Pt. I: Extractions 101

Cannabis concentrates have been used throughout human history. Their current meteoric rise in popularity is due, in large part, to modern technology and the ingenuity of cannabis consumers, which have jointly ushered us into the golden age of concentrates. As one Michigan dispensary owner observes, “Concentrates have taken over the cannabis community.” According to Rhory Gould of the Arborside dispensary in Ann Arbor: “Concentrated cannabis can generate up to 40 percent of our sales in the form of wax, oil, hashish, kief, e-pens and edibles made with concentrates.”

Those are the facts. But exactly how and why this happened merits examination—and, most importantly, so does the question of what this means for the future of cannabis. Exploring the most popular types of concentrates, how they’re made, and the history of concentrating cannabis can provide a better understanding of the current market and where it’s headed.

A Brief History of Cannabis Concentrates

Concentrates have been around for thousands of years, in several different forms. Cannabis first appeared in China around 6000 BCE as a food and textile source. Its use as a concentrate made its first appearance around 1500 BCE as bhang: cannabis ground into a concentrated paste, then mixed with herbs and either ghee or milk, or left as a chewy ball and eaten. Somewhere around the 12th century CE in the Middle East, hashish—dark, malleable and resinous chunks of concentrated cannabis—became wildly popular. Hashish made its way along the trading routes through Asia and eventually Europe, becoming a highly coveted global commodity.

In the United States, concentrated cannabis appears in the mid- to late 19th century in the form of  “marihuana” tinctures. These alcohol and ethanol extracts mixed with other herbs were sold as a cure-all for toothaches, impotency, typhoid fever, baldness and just about anything else you can imagine. Whether they made their way to the public via doctors or were peddled by hawkers and “snake-oil” salesmen, people knew that cannabis was a medicine, even if they didn’t understand the science behind it yet. Indeed, it wasn’t until the 20th century that cannabis began to be demonized through government propaganda and appeals to racism, becoming federally illegal in 1937 as a result of Harry Anslinger’s anti-pot campaign and the subsequent Marihuana Tax Act.

Hashish became popular in the US during the 1960s and ’70s, mostly due to the hippie counterculture. Jack Kerouac published On the Road in 1957, inspiring a generation to leave home and embark on a journey of self-discovery. This led, in turn, to what became known as the Hippie Trail: a popular route from Europe to Kathmandu through Turkey, Pakistan, Afghanistan, Iran, India and Nepal. Adventurous American tourists discovered a hashish mecca as they followed the trail through the different regions, each with its own distinctive strains developed over the ages. They brought back “new” landrace genetics in the form of seeds as well as high-quality import hash, creating a willing and eager marketplace in the United States. Combine this with the hippie culture of anti-establishment politics, free love and expanded consciousness, and the result was a love affair with cannabis. (Not coincidentally, High Times and its smuggler-founder, Tom Forçade, who started the magazine in 1974, played a role in fostering this interest in the concentrated herb.)

The 1970s and ’80s saw vast amounts of cannabis grown stateside for the first time, as farmers and smaller growers switched over to a more popular cash crop. Western cultivators embraced these ancient genetics and began to develop the highest-quality cannabis ever seen. The dissemination of cultivation discoveries and techniques and new extraction methods was mainly relegated to underground newspapers and books until the 1990s, when online forums, grower groups and chat rooms emerged.

Then, in 1996, California passed Proposition 215, creating a safer, semi-legal framework under which cannabis could be grown. A newly legal marketplace gave concentrates a platform to be displayed and sold, albeit slowly at first. Growers with vast amounts of after-market material left over, such as trim and lower-branch buds not fit for sale, suddenly found great value in these for creating extracts. Better yet, with the amount of cannabis now being grown, there were also plenty of high-grade buds to extract with newer and more promising methods.

Non-Solvent vs. Solvent Extraction

Both dry-sieving and water extraction are non-solvent extraction processes. Extracting water hash is gentler and more selective, resulting in a more refined concentrate than the original hash from overseas. Import hash was made in places like Morocco and Lebanon by dry-sieving: beating the plants against a surface (such as a silkscreen), then collecting the trichome droppings and pressing them into slabs.

Both water extraction and dry-sieving collect the coveted resin glands, but the older method also collected pistils and other bits of plant matter and foreign material that diluted the potency (kief typically has from 35 to 50 percent THC, as compared to water hash, which usually ranges from 50 to 70 percent THC). As a result, water hash—once a concentrate that only growers or those higher in the food chain had access to—soon became a popular and sought-after product.

Up until 2009, mostly water hash (or bubble hash, as it came to be known) and various kief products could be found on dispensary shelves in the US. Some concentrates made with solvents were available, but most were subpar and stayed fairly unnoticed. It wasn’t until 2010, when the first US Cannabis Cup was held in San Francisco, that these newer types of concentrates first appeared in a Cup competition, thereby introducing “dab” culture to a broader audience.

Full-melt water hash
Full-melt water hash

Butane honey oil (BHO) and alcohol-derived oils joined the more traditional forms of extracts and blew open the public’s perception of what concentrates could be (solvent-extracted hash generally hovers around 80 percent THC, but some highly refined oils can reach upwards of 98 percent). Previously, behind the scenes, some growers were making head-stash oil with solvents like butane or alcohol—but with lower yields and the lack of a convenient means to smoke it, it remained mainly the stuff of legend for the larger cannabis community.

In particular, the highly refined BHO and alcohol oils became popular due to their higher-THC content and strength. The only problem was how to smoke it: No matter what form BHO takes—oil, moonrock, wax or budder—it becomes a runny liquid when heated, clogging screens and pipes and rendering traditional smoking methods useless. Hot-knifing on a stove, dropping onto hookah coals, or just adulterating joints and bowls were inefficient means of consuming such a high-quality product.

Cue the Nail

Late in 2009, some ingenious tokers began rigging bongs with a small metallic plate affixed to an arm that, after being heated, swung down below an inverted, bell-shaped intake bowl. Oil was then applied to the hot plate and the vapor sucked in through a water pipe, giving the world its first semblance of an oil rig.

Still, few people had one. It wasn’t until the end of 2010 that swing arms had been replaced by glass and titanium nails that sat right in the existing stem of a bong. Driven by the popularity of oil, glass rigs were crafted specifically for dabbing, breathing new life into the world of glassblowing. Given this brand-new tool to smoke oil with, and the introduction of a more refined (and cleaner) product to the public, the love affair with concentrates began to boil over and change the cannabis community forever.

The Art of Extraction

The precipitous ascent in the popularity of concentrates has fueled the progress of cannabis extraction. Dabs are basically the extracted and collected cannabinoids of the plant (THC, CBD, etc.) as well as its terpenes, or essential oils. These concentrates are refined and purified enough that a small dab on a hot nail leaves little to no residual plant matter behind (i.e., no ash, as with a joint).

CO2 oil
CO2 oil

The majority of cannabinoids and terpenes are found in the trichomes, the glandular stalks and bulbous heads that exist on the cannabis plant. Terpenes are the essential oils that give cannabis its different flavors and aromas and help to shape the experience of the high. The terpenes and cannabinoids have different boiling points (i.e., the point at which they turn into a gas). This is why, before processing, it’s very useful to keep the cannabis and its surrounding environment cold, as this will help retain the volatile terpenes, which can easily evaporate even at room temperature. For this reason, many growers immediately freeze their trim or buds right after harvest, giving rise to the term “fresh-frozen” among extract artists and growers.

“Live resin” is the term for another extraction method that involves harvesting the plant and immediately processing it while still “alive” in order to best retain the essential oils before degradation begins. As the rule of thumb for nearly all extraction methods states: Your final product will only be as good as your starting material.

Cannabinoid & Terpenoid Boiling Points

During the purging process, which removes the solvent from the extract, it’s important to remember that under vacuum, the boiling points of cannabis’s various compounds drop significantly. For example, carophyllene’s boiling point is 246°F at standard atmospheric pressure, but when put under full vacuum, it can drop to 109°F, creating a window for removing the solvent while retaining as much of the cannabinoids as possible. However, pesticides and other chemicals can’t be removed by purging, nor can they be eliminated by winterizing or distilling. Indeed, all elements and compounds present in the plant—good and bad alike—become concentrated during the extraction process, which is why it’s crucial that the source material never be exposed to harmful substances.

Compound         Boiling Point (°F)        Medicinal Properties

THC                         315°F                                   Anti-inflammatory, analgesic, antidepressant

THC-A                     220°F                                 Sedative, antitumor, anti-nausea, antidepressant, anti-epileptic

CBD                         356°F                                  Antipsychotic, anti-inflammatory, anti-oxidant, anti-seizure, pain relief

CBN                         365°F                                  Analgesic, antispasmodic, anti-insomnia, sedative

CBC                         428°F                                  Antibacterial, anti-inflammatory, anti-anxiety, bone-growth stimulant

Caryophyllene       246°F                                  Anti-inflammatory, antidepressant

Limonene               349°F                                  Antidepressant, immunity booster

Myrcene                  334°F                                  Antibiotic, anti-inflammatory, antitumor

Linalool                   388°F                                 Insomnia and chronic-pain relief

Pinene                      311°F                                  Anti-asthmatic, anti-inflammatory, bronchodilator, stimulant

Cineole                     349°F                                 Antibiotic, antiviral, stimulant, increases blood flow


Non-Solvent Extractions

Closer to the traditional methods of hash-making are non-solvent extractions. These techniques essentially harvest the trichomes via a manual separation process. While not as selective as some solvent extractions, these techniques can provide the least-adulterated end product and will appeal to those people who want to remain as “natural” to the plant as possible. This is because the use of solvents leaves behind residual amounts that need to be purged from the concentrate (more on this in a bit), whereas non-solvent extractions use dry-sieving—or only water—to extract the plant’s resin. Here’s a breakdown of the most common forms of non-solvent hash:


The easiest method of extraction, kief is made by working cannabis over a screen to filter out the trichomes. Dry ice can be used to freeze the trichome stalks, allowing them to break off more easily. A gentle working over the screen will produce a light-colored kief. Too much agitation will break down the plant matter enough to pass through the screen, darkening and lowering the quality of the final product. Different-size screens are used to separate full trichomes from broken stalks and gland heads.

Storage in a cold environment and sealed package can keep kief light in color with a sandy consistency. Improper packaging can cause oxidation and darken the kief, while warm temperatures will cause the resin to melt out of its casing and become a big clump. If extracted properly, lightly worked kief from fresh material stored in a cool environment can certainly rival the best concentrates in the world in terms of flavor, but less so in potency.

Kief in a jar
Kief in a jar

Water Hash/Bubble Hash/Full Melt

Water hash uses a screen and water as a carrier agent to separate the trichomes from the plant matter. Very cold water, full of ice, fills a bucket lined with different-size filter bags whose bottoms consist of various screens with holes measured in microns. The plant matter is submerged in the freezing liquid and carefully agitated to break off the now-brittle trichomes. These pass through the filter screens, with each bag allowing different-size pieces to pass through, resulting in a slurry at the bottom of each one containing full trichomes, broken stalks and gland heads. Hand-stirring the cannabis with a wooden spoon is gentler (and thus better) than using a mechanical mixer or automatic “washing machine,” resulting in a higher grade of concentrate. Even the shape of the ice cubes will affect how roughly the plant material is treated.

Carefully breaking up the collected mass of trichomes to remove the water without losing the coveted terpenoids and essential oils takes a sharp eye and can make all the difference. Microplaning and sifting are ways to gently separate and remove water using sieves, spoons and rasps without damaging the whole trichomes, thereby retaining as much of their essential oils as possible. “Water hash” refers to the process by which the concentrates are made, while “bubble hash” and “full melt” refer to the end product. Bubble hash is water hash that bubbles when smoked due to its high oil content; full melt is slightly more refined, melting away without any plant residuals left in the bowl (or on the nail) when smoked.


Rosin technology is the latest evolution in non-solvent hash-making. To extract “rosin” from cannabis, pressure and a slight amount of heat are used to expel resin from the trichome glands. Here, cannabis is put into a filter pouch and then placed onto a slightly warmed press that squeezes out the extract. Higher temperatures (180°F to 330°F) and more pressure can result in higher yields but can also degrade the final product. The more heat that’s applied, the more terpenes become gas and escape. The starting material also plays a huge role, as a good kief or water hash can result in higher-quality rosin than can be obtained from flowers, delivering a more potent, dabbable concentrate. Rosin can be produced quickly, safely and on demand, making it a viable alternative for people who want to enjoy dabs but don’t have access to the professionally produced product. Creating rosin can be as simple as placing buds between parchment paper and pressing it out with a hair straightener.

Solvent Extractions

Solvents are liquids in which another substance is dissolved, thus creating a solution. The various solvents have different polarities and water solubility, which can pull different combinations of compounds from the cannabis plant, affecting the extract’s color, consistency and flavor. Some solvents can be flammable and explosive and should be used only by professional extract artists in facilities with the proper equipment. Solvents can strip almost all of the cannabinoids from cannabis while pulling less plant matter than non-solvent methods, resulting in a very clean and pure flavor. Due to this selectivity, solvent extractions can have some of the highest THC and terpene levels. Highly skilled extract artists can further remove terpenes and other cannabinoids to create a nearly 100 percent THC product.

Creating safe, high-quality solvent extractions also depends on proper purging. There’s a wide range of solvents used for extraction, such as butane, pentane, hexane, ethanol and so on. Varying boiling points make some solvents easier to purge from the final product than others. The following list provides a closer look at the three most popular solvents in use today.

Isopropyl Oil/Quick-Wash ISO

Isopropyl alcohol has a high polarity and is water-soluble, making it one of the least-selective solvents. Using well-dried and well-cured cannabis can help decrease the amount of chlorophyll and moisture pulled from the material. “ISO oil,” as it’s commonly known, is created by filling a vessel with cannabis, which is then soaked in isopropyl alcohol and lightly shaken. The longer the mixture is shaken and steeped, the more cannabinoids are extracted—but so are chlorophyll, plant alkaloids and waxes. Depending on the starting material and the quality desired, the cannabis is soaked anywhere from a minute to a few hours, after which the solvent is strained into a dish. The remaining solvent is then evaporated from the extract in a vacuum oven by bringing it to its boiling point (just under 181°F) for several hours to a couple of days to ensure that all of it is removed, leaving behind a powerful oil rich in THC.

Butane Honey Oil (BHO)

Already common in the fragrance and food industries, butane extraction spread like wildfire because of the potency and terpene retention achieved, as well as its relative ease of use. N-butane’s polarity matches very well with the compounds that people enjoy in concentrates.

Stuffing a long column with cannabis, wrapping a filter on one end and spraying cans of butane to extract the cannabinoids doesn’t take much knowledge or skill, yet this method can produce tasty golden oil testing at nearly 80 percent THC. However, BHO extractions can be very dangerous, because all “-tane” solvents are highly flammable, and explosive compounds should not be used without the necessary lab facilities and tools.

Properly made BHO is extracted in closed-loop systems that are essentially two vessels with a column packed with cannabis in between. The solvent stays sealed (and under pressure to retain liquid form) as it passes from one vessel through the plant material into the “catch vessel.” Hoses return the solvent back to the first vessel, leaving behind a concentrated slurry awaiting its purge. This system not only captures the solvent for reuse, but also keeps the process safer by preventing it from encountering the open air.

N-butane has a low boiling point of 31°F. Using dry ice to keep the solvent cold and in its liquid form aids in a thorough stripping of the cannabinoids. Extract artists purge the resulting concentrate in a vacuum oven to eliminate the residual solvent, while keeping the temperature low enough to retain those terpenes with low evaporation points. Oftentimes, extractors will mix their butane with up to 20% propane, as the polarity of propane helps to pull a slightly different mix of compounds from the cannabis, leading to a more complete extraction.

Butane honey oil

CO2 Oil

In order to harness CO2 for extraction, it must be kept in a container under high pressure to create a supercritical fluid. This fluid keeps the chamber full like a gas, but with the density of a liquid as it washes over the cannabis. CO2 extraction units can be expensive, as they are enormous in size in order to deal with the high pressures required. Due to the water solubility of CO2 and the low temperature used, the wash will produce a cold slurry much like a frosty. Its extremely low boiling point of –56°F makes purging the solvent from the concentrate very easy. A low-heat purge to eliminate the water content results in an extract that frequently has a runnier consistency, sometimes with a slightly fruity tinge in taste. Due to this final consistency, CO2 oil is often used for prefilled e-pen cartridges.

The Purge

As mentioned earlier, different boiling points make some solvents easier to purge than others. Vacuum ovens adjust the temperature as needed while also raising the atmospheric pressure inside, flattening and stretching the concentrate to create more surface area. This allows for the easier off-gassing of the solvent.

The temperature settings not only help the solvent turn to gas, but also keep the material viscous enough for the solvent to escape. Ensuring the complete removal of solvents while retaining the terpenoids can be a delicate balance. Consistencies can also be controlled by different temperatures (anywhere from 80°F to 180°F), the length of the purge, and how much vacuum (suction) is applied. All of these factors control the ratio of cannabinoids and terpenes that remain in the concentrate. Higher temperatures and longer exposure times can create drier concentrates, but also lower terpene counts. Whipping the final product over a low heat can produce a creamy-looking budder or, if dried further, a waxy crumble. Bring that same crumble back up to a higher temperature and it will un-aerate, flatten out, and become a liquid or shatter, depending on the cannabinoid ratios. Many unstable concentrates will nucleate, with the oxidized terpenes (now called terpenoids) eventually separating from the resin.

Too many plant waxes and fats will also affect the final product’s consistency. Since they don’t add anything to the psychoactive effects and can make dabs harsher, these plant waxes and fats can be removed via a simple winterization process. This involves filling a sealable vessel with solvent (primarily isopropyl, methanol or denatured alcohol), to which the concentrate is added and stirred to fully incorporate it. The vessel is then sealed and placed in a freezer overnight. All of the heavier plant waxes, fats and lipids will settle to the bottom, leaving the oil suspended in the alcohol solvent. The liquid is carefully poured off so as to not disturb the wax at the bottom; the concentrate is then returned to the vacuum oven to remove the residual solvent, leaving behind absolutely pure cannabinoids for consumption. Based on the ratios, the final product is either a glasslike shatter or a viscous, honey-like oil.

Looking at how concentrates are made provides a better insight into their fundamental properties and differences. This knowledge will prove beneficial when selecting the types of concentrate you enjoy. Stay tuned for Part 2 of this series, in which we’ll further explore the subject, including non-cannabis additives, terpenes, the isolation of specific cannabinoids, and how best to consume your concentrates.

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