OVERVIEW OF POPULAR CANNABIS EXTRACTION METHODS
by Casey McGarvey
Ethanol (3.)
Ethanol, drinking alcohol, or ethyl alcohol all refer to the harsh smelling, tasting, and
pleasantly intoxicating liquid that most people around the world are familiar with in one way or
another. If you were to step into a pharmacy 100 years ago or more, you would be shocked by
the quantity and diversity of medications, nearly every one of them being an ethanolic solution
of one or more plants, a tincture.
The concentration of plants properties utilizing ethanol is not a new idea. The process
has been practiced and improved by humans for millennia. The etymological history of the term
‘spirit’ when referring to strong alcoholic drinks comes from this ability of alcohol to seemingly
grab the spirit or essence of the plant you immerse in it.
When it comes to cannabis, the story is no different. You would have been able to find a
cannabis tincture (ethanol solution) in almost every reputable pharmacy across the entire
modern world until around the beginning of the 20th century. Why this is no longer the case is a
fascinating chapter in the history of cannabis, plant medicine, as well as human freedom that
we’ll hopefully be able to discuss at length in the future.
However, even though these tinctures were no longer readily available and legally
purchasable, that does not mean that they were no longer manufactured in, now illicit, labs
across the world. Even some parts of the world have essentially never had a prohibition on
cannabis similar to the U.S. for various medical, rational, and religious reasons. Through these
two strongholds, cannabis extraction lived on and thrived during its supposed prohibition.
Basic Process:
To obtain a cannabis tincture similar to those used and sold in these historical
pharmacies, all that is necessary is dried and resinous cannabis flower, strong alcohol
such as vodka, and preferably a means of filtration. The cannabis flower is ground and
then soaked in the ethanol for a specified amount of time (mostly dependant upon the
temperature of the ethanol – our solvent). Finally, the cannabis flower (the solid phase) is
separated via filtration from the solution: Viola, a genuine 20th century and earlier
medicinal staple.
This is perhaps the most simple S.O.P. for ethanol cannabis extraction. It has been
undoubtedly used for centuries, and it works surprisingly well. The only aspect of this process I
don’t mention here is that of Decarboxylation which we’ll dive into another time. The next
innovation to this process came from evaporating the alcohol and water from the solution to
collect the extract. It’s unclear when this method became widely used. Still, at the beginning of
the 21st century, a crude ethanol extraction of cannabis (as detailed above) was popularized by
a man named Rick Simpson and affectionately referred to as Pheonix tears or, more commonly,
Rick Simpson Oil (R.S.O.).
Interestingly, however, all through the 20th century’s rich history of clandestine cannabis
growing and manufacturing ethanol extraction had a bad reputation. Even at the outset of the
21st century, when cannabis was beginning a truly epic resurgence into popularity and practical
medicine, R.S.O. was known as a powerful medicine but not ever sought after by the
recreational enthusiast.
This is because R.S.O. resembles in some ways the nasty, sticky, black resin you would
get from cleaning a pipe. Admittedly much cleaner than pipe resin, it is still not appealing to the
eye, nose and not enjoyable to smoke. If you need strong medicine, it’s almost ideal, but if you
are a connoisseur who enjoys the complex nflowery taste of smoking a joint and some grade-A
hash, then this is not at all what you’re looking to enjoy.
Why is that? And what has changed in the past 20 years since Rick’s time that has made
ethanol extraction such a popular method?
When the evolution of ethanol extraction is looked at from this point forward, two distinct
changes in technique and process allowed ethanol to transform from the unpopular but valuable
to the necessary.
First was the understanding and application of fractional distillation.
And perhaps most importantly, next was performing the extraction with very cold ethanol.
Fractional Distillation (4.)
Distillation is one of the most important techniques chemists have at their disposal when
separating and purifying various compounds. When you distill a complex solution, you attempt
to separate the components based upon their respective boiling points.
With extraction, as we’ll see in further detail shortly, we are also separating components
from one another, but not based upon their boiling points. Solvent-based forms of extraction
separate various compounds based upon their chemical polarity. But as you would assume
and will see very quickly after working in a lab, separating molecules based upon chemical
polarity via extraction will only get you so far.
The combination of these two different methods of separation allows chemists to refine
most chemicals to a high level of purity.
Simple distillation is straightforward. We take a solution and begin slowly heating it in a
boiling flask, above which is situated a column and sometimes a condenser in which the vapors
will rise, pass through, condense back to a liquid state, and be collected in a collection flask. As
the temperature increases, different compounds will boil off (based upon their boiling points),
and the solution may be crudely fractionated by collecting the various components that
condense separately.
This process is relatively easy to perform, especially when the components you want to
separate (1) boil at quite different temperatures and (2) boil at relatively low temperatures.
Distillation becomes a bit more complicated when the boiling point of your substance is, under
normal conditions, well above 300˚C, as is the case with our Cannabinoids. This is when
vacuum distillation is required.
Without diving too deep here, put simply, the temperature at which a molecule will
evaporate/boil or shift phases from a liquid to a gas is a function of the environment’s pressure.
The higher the pressure of the environment, the more temperature or kinetic energy will be
required to cause the molecules to boil. In the same way, however, if we were to reduce the
pressure of the environment in which our solution is contained, we would need to apply less
temperature to cause the same shift.
This is the critical piece of understanding to perform a vacuum distillation. This is also
particularly important and useful to us because not only would reaching the temperatures
required to perform a simple distillation of cannabinoids be dangerous and difficult, these
temperatures would degrade (break down) a lot of the other components in the solution –
resulting in a low-grade product. With a vacuum applied, though, we are able to distill
cannabinoids at temperatures closer to 200˚C, which is much more manageable.
Vacuum distillation can be a bit intimidating for new operators. Simple distillation itself
can be daunting, and vacuum distillation makes the process much more efficient but does so by
adding a whole other variable (vacuum depth) an operator must be aware of and manipulate
appropriately. It was in part due to this, and on the other hand, due to the relatively expensive
gear required to perform an efficient vacuum distillation, that delayed the application of this
technology to the world of clandestine cannabis chemistry.
However, sometime probably in the 90s or early 00s, cannabis was becoming popular
enough to garner the attention of college chemistry students as well as veteran chemists looking
to partake in the plants’ medicinal qualities as well as capitalize on their ability to apply their
knowledge to this area of clandestine and esoteric science.
Truthfully there was something of a convergence happening. Before we dive into the
next technical advancement (that of cold ethanol extraction), there is an even more important
facet of the industry that was fundamentally changed by the application of ethanol extraction.
Without it, the extraction industry would not exist in the form it does today.
In Partnership with Rocky Mountain Extracts