What are Solvent Extracts?
Whereas all solventless concentrates are extracted via mechanical means, be it agitation or heat and pressure, we can also make cannabis concentrates with a wide range of chemical and organic solvents, most commonly butane, propane, ethanol and CO2. This process works by dissolving the trichome heads in the liquid solvent which is separated from the plant material and purged (evaporated off) in a vacuum oven or dessicator and vacuum pump to ensure we are left with a pure resin extract with as little residual solvent as possible. Solvents are divided into two groups, polar and non-polar, with non-polar solvents like butane readily dissolving non-polar compounds from the plant, in this case the oils and lipids making up the trichome heads. Polar solvents like Ethanol however will extract both non-polar and polar compounds, meaning water-soluble compounds like chlorophyll are more likely be extracted alongside cannabinoids and terpenes. Many of the solvents used in extractions are highly flammable, meaning only the proper equipment should be used to extract and purge, and additionally a high level of safety and care must be taken to avoid accidents at all stages of the process.
BHO (Butane Honey Oil)
Hugely popular across the cannabis world, and probably the most widespread of all extracts. At its most basic, this is a process by which resin is extracted from plant matter by being dissolved in butane, and then purged with heat under vacuum to remove all the gas and leave a high-purity cannabis concentrate. Butane’s relative non-polarity means it doesn’t extract water-soluble compounds like chlorophyll, resulting in one of the cleanest extractions possible.
People have been making cannabis oil with butane for many years but developments in extraction equipment and techniques within the industry have, over time, led to better quality products with higher purity and far less contamination from residual solvents etc. As a result, the choice of different butane extractions has widened drastically, with dispensary menus showing a range of different textures such as budder, wax, shatter, batter, sap, syrup, sugar, pull & snap. These various textures depend on a combination of factors: the genetics processed; terpene content; purging techniques; post-extraction manipulation. As a general rule, shatter type extracts have a higher THC content and less terpenes than other textures, leading to a stronger effect but with less intense flavour.
This is currently a hugely popular form of BHO extracted from freshly cut, flash-frozen buds to create an intensely flavoured concentrate that truly captures the essence of the live plant. Notable for its sticky, syrupy texture due to the high terpene content. Read more about it in our dedicated article here.
Terp Sauce or HTFSE & HCFSE
Probably the most recent trend in concentrates is the development of these new sauce-like extracts with extremely high terpene content. HTFSE (High Terpene Full Spectrum Extract) and HCFSE (High Cannabinoid Full Spectrum Extract) are the results of carrying out a long, slow and low vacuum purge at low temperatures on solvent extracts made from high quality cannabis flowers, which must have a high percentage of terpenes. During this process, which can take three weeks or longer, the oil separates, with the THC-A crashing out of solution and crystallising to form something that looks like diamonds swimming in a viscous, honey-like, golden liquid made up principally of terpenes but also containing the full spectrum of secondary cannabinoids and flavonoids for a more complete effect. HCFSE will have a THC-A content of around 90% and will look more like diamonds coated in sauce, whereas to qualify as HTFSE, it must contain between 13% to 25% terpenes and have the appearance of a very runny honey with crystals in it, and will be of a more liquid consistency than HTFSE.
PHO or Propane Honey Oil
Less commonly available than BHO, Propane Honey Oil is made in much the same way, simply changing butane for propane, which extracts slightly different ratios of cannabinoids and waxes. It has a much lower boiling point than butane, so can be purged easily without affecting the terpenes, meaning PHO often has that budder/wax texture we associate with terpene-rich concentrates. Propane is much more costly than butane, so many professional extractors will often use a blend of both gasses to achieve optimum efficiency.
Cannabis resin naturally contains neutral, non-active ingredients like waxes and lipids, which have no medicinal effect and are thought (although there is very little evidence to support this) to possibly provoke certain respiratory issues such as Lipid Pneumonia. For this reason, much focus has been put on producing the cleanest concentrates possible and removing these waxes, particularly for medicinal products destined to be inhaled. Initially a much more complicated dewaxing process called winterisation was used, involving a secondary solvent, usually ethanol, and subsequent cold filtering. While this is very efficient at wax removal, during the process the terpene content of the final extract is greatly reduced, limiting the therapeutic potential. Nowadays more extractors are carrying out the dewaxing as part of the initial butane extraction process, at much lower temperatures so that the lipids form solids and are easily filtered out. This column dewaxing technique doesn’t remove as many waxes as winterisation, however it does preserve the terpenes perfectly, delivering a clean and great tasting BHO.
Short for Quick Wash Ethanol and Quick Wash Iso, these are extractions made with alcohol, and are the simplest and safest way for home-users to create their own solvent cannabis concentrates. The relative ease of access, low cost and low flammability make alcohol ideal for extraction novices just beginning to make concentrates. The two alcohols available are: Ethanol, the same alcohol present in alcoholic beverages, produced from the fermentation of yeast and sugars; and Isopropyl alcohol, produced via a chemical process combining propene and water, and is not safe for human consumption. For this reason and for the sake of your health, we advise making or consuming only alcohol extracts made with Ethanol. Ethanol extractions will vary in quality according to the starting material used and also to the length of time the cannabis is in contact with the solvent. Short washes (under a minute) will produce a shatter-textured cannabinoid rich extract of high purity that, once cold-filtered (winterised) and purged, will be suitable for dabbing or smoking, although the terpene levels won’t be nearly as high as with BHO. If however, the cannabis is left soaking in alcohol for an extended period of time, additional compounds like waxes, chlorophyll etc. will be extracted and the resulting oil will be dark and viscous, similar to Rick Simpson Oil, a product that’s great for oral consumption and topical application by therapeutic patients but entirely unsuitable for dabbing or smoking recreationally.
Much touted as a safe alternative to butane for cannabis extractions, there’s been a lot of hype recently over DME. Manufacturers claim it is much safer due to its high purity, low toxicity, reduced flammability (although it is still highly flammable), and low boiling point (leading to suggestions it can be purged without vacuum – not recommended.). Another quality of DME is that it extracts a much wider range of compounds than butane, producing extracts with higher cannabinoid and terpene content than butane, but with a notably darker colour due to the greater quantity of undesirable compounds such as chlorophyll that is extracted alongside the cannabinoids. While DHO has become reasonably popular for DIY home extractions, it has yet to find its place in the arsenal of tools used by professional extractors, and is not something you’ll find available in too many dispensaries.
One of the most widespread methods among professional laboratories and requiring a huge investment in scientific equipment, extracting with Carbon Dioxide results in the cleanest, most residual-free of all solvent extracts, significantly safer than BHO. However, the disadvantage of CO2 oil is that many terpenes are often lost during extraction, meaning these extracts tend to have a nondescript, homogenous flavour regardless of the strains being processed. For this reason, a large proportion of the CO2 oil produced is used either in edible products and most commonly in tincture-type oils, where flavour is less of an issue. Most CO2 oil however, is blended with added terpenes and loaded into vape pen cartridges in what is easily becoming today’s most popular and widespread method of consuming cannabis concentrates.
Solvent-free concentrates – Distillates and Isolates
Many believe that this is what the future of cannabis will look like, as its use extends to the general populace, very few new adopters will be smoking blunts or dabbing globs of “errrl”. Those who want to consume cannabis via inhalation are much more likely to be attracted by the convenience of a discreet vape pen, but the vast majority will be looking for edibles, medibles and products which can be easily dosed. Cannabis distillates and isolates are increasingly common products in the growing legal markets in the USA. A laboratory technique known as Short Path Distillation is employed to further purify and separate cannabis extracts, either solvent or solventless, cleaning them of any residual solvents, pesticides, waxes and lipids to create a high purity extract and one of the most expensive products on the market, due to the lengthy process involved in their production.
These are viscous, runny liquids containing fully activated cannabinoids in levels as high as 99% with no measurable terpene content. They have a colour ranging from almost clear to light gold to amber and can be smoked, dabbed, eaten or incorporated into cookery recipes. Most often though, distillate is re-combined with terpenes and used to fill vape pen cartridges. There are mixed opinions about distillates, on one hand they are seen as a highly useful product when sourced from good quality extracts, allowing patients to accurately dose cannabinoids and ensure effective medication. On the other hand many criticise distillation as an easy and profitable way for producers to recoup something from all the “dirty” oil that doesn’t make it to the market: poorly purged extracts from badly grown crops that would otherwise fail screening for residual solvents, prohibited pesticides and other impurities. Time has shown that the quality of the end product depends on the quality of the material used, so for this reason more and more processors choose to use only the best extracts from organic grows in the preparation of their medicinal distillates.
While the initial distillation process separates the cannabinoids from the terpenes, waxes and lipids in the original extraction, Isolate is the result of further purification of these decarboxylated cannabinoids. To make CBD Isolate, a secondary solvent and chemical process are employed to produce 99% pure CBD crystals from the distillate. THC-A Isolate is a laboratory-grade product made via a fairly complicated procedure involving the use of various chemicals including methanol, and the techniques of rotary evaporation and chromatography, but a rudimentary kind of THC-A crystal can be produced from raw BHO with a high terpene content by slowly evaporating the terpenes at low temperatures and waiting for the crystals to “crash out” of solution, however there are fears that, if not performed properly, this method can leave residual solvents inside the crystals. Indeed, over the last year or so some extractors have begun to make a kind of non-solvent THC-A by re-pressing high quality rosin wax/budder at very low temperatures and pressures just enough to melt away the majority of the terpenes, leaving a pale coloured, crystal/wax type product with very little flavour but a very potent effect. Yields, however are very low indeed with this last process.
Well, hopefully this has cleared up any confusion you might have had, and now you’ll better equipped to make the correct choice of cannabis concentrate for your own particular tastes and needs!
Happy dabbing or smoking!
Publications referenced for this article:
- Marijuana Business Daily: Sales of marijuana concentrates, edibles surging in Colorado
- Forbes: California Cannabis Retail Market Revealed: Big Data Tells All
- Lumír O. Hanuš, Rina Levy, Dafna De La Vega, Limor Katz, Michael Roman & Pavel Tomíček: The main cannabinoids content in hashish samples seized in Israel and Czech Republic
- Low Temp Plates: Solventless THC-A separation tutorial
- Dimethyl Ether toxicology report
- n-Butane toxicology report
- Master Organic Chemistry: Polar Protic? Polar Aprotic? Nonpolar? All About Solvents
- A Wohlfarth, H Mahler, V Auwärter: Rapid isolation procedure for Δ9-tetrahydrocannabinolic acid A (THCA) from Cannabis sativa using two flash chromatography systems
- Dilini Vethanayagam, Stewart Pugsley, EJ Dunn, David Russell, J Michael Kay, Christopher Allen: Exogenous lipid pneumonia related to smoking weed oil following cadaveric renal transplantation.