Kosher vegetable glycerin is an effective method for extracting cannabis concentrates directly from the plant material and produces a tasty medication that is easily ingested directly orally, or mixed with drinks and food.
Glycerin is a heavy, syrupy clear liquid sugar alcohol that has approximately 60% of the sweetness of sucrose, and about the same food value.
It is however not actually a true sugar and is often used as a sugar substitute, as diabetics are often able to use it without experienced the blood sugar rollercoaster they suffer with sucrose or other sugars.
Glycerin makes an extremely tasty and provocative cannabis tincture, that when made using cold extraction methods, is reminiscent of wild honey, as it preserves all the individual flavors, so that they dart off in all directions simultaneously.
Hot glycerin extraction also makes a tasty tincture, with the flavor more resembling a fine soup, where the individual flavors are married into one overall flavor. While not as whimsical and provocative as a cold extraction, it can be prepared start to finish in a couple days, where cold extractions take a minimum of 60 days and are commonly soaked for 120 days or longer.
Many of the provocative flavors and odors from cannabis are aromatic terpenes, and the reason that they are aromatic in the first place, is that they give off molecules at room temperature.
Heating speeds up the rate that the accompanying terpenoids and other aromatics are vaporized off, so many are collateral damage in a hot extraction and are lost.
The glycerin molecule is actually only a three carbon molecule chain, with three hydroxyl groups (OH) attached, and as hydroxyl groups are hydrophilic, glycerin is hygroscopic (absorbs water) and dissolves readily (miscible) in water.
It has a flash point of approximately 177C (351F), and a boiling point of 290 °C (554°F).
It is relatively non toxic. The MSDS tells us that the LD50 Oral rat dosage is 12,600 milligrams per kilogram of body weight, which is approximately 5.7 grams per pound of body weight, or 36 ounces for a 180 pound male.
By comparison, acute oral toxicity (LD50) Oral Rat for sucrose sugar is 29700 mg/kg and about 7060 mg/kg for ethyl (grain) alcohol.
At saturation, Glycerin only hold as 33% as much cannabis oil as the same volume of ethyl (grain) alcohol, so about three times more is required per dose.
To reach maximum saturation however, requires processing more than one batch of fresh material through the glycerin, because as the saturation level increases, the glycerin becomes less aggressive as a solvent and the partially dissolved cannabis boundary layer interface with the solvent is also no longer at full strength and as reactive.
To keep the reaction from slowing to a snails pace, or even stopping, some method must be used to keep removing this stagnant layer and refreshing the boundary between the solvent and resin.
In addition heat dramatically affects resin dissolution rates. The hotter it is, the faster it works, up to the point of overheating.
As glycerin is usually used as an oral med, we also need to consider decarboxylating the cannabinoids so that they are orally active.
If not in excess, some water solubles add to the flavor of a glycerin tincture, and taking all of the water out of the material before processing it, makes it frangible and prone to breaking into small fragments that may be hard to remove.
Let’s look at how these four variables can be manipulated to produce delicious and effective glycerin tinctures.
Drying and decarboxylation:
Plant material is typically dried to around 10/15% water content by weight for smoking and vaporizing purposes, which is low enough to make some delicious glycerin, but for those who prefer less water solubles in their glycerin tincture or wish to decarboxylate the material before extracting, you may add a drying and/or decarboxylation step.
To simply remove most of the remaining moisture, I place the plant material on a cookie sheet in a 200F oven and turn it, until it is frangible when I roll it between my finger and thumb.
At that point it is ready for extraction, but if you also wish to decarboxylate the plant material before making your tincture, you can then crank up the oven to 250F and after it stabilizes at the higher temperature, replace the plant material in the oven and hold it at temperature for approximately 30 minutes
That will add a roasted flavor to the tincture and many of the turpenoids will be lost, but it will decarboxylate approximately 70% of the existing carboxylic acids into their non acid orally active form.
An alternative to decarboxylating the material ahead of time, is to do it after the extraction is complete and the plant material has been filtered out. That eliminates the roasted flavor and preserves more of the turpennoids.
Elevating the temperature of the glycerin increases the rate of dissolution of the resins, especially if you raise the temperature high enough for the resins to be molten. THC, CBD and CBN are all molten at just under 180F, so we operate at that temperature.
The advantage of using as low a temperature as possible, is that fewer aromatic terpenoids are boiled off at that low a temperature, and it decarboxylates more slowly, so that the process doesn’t pass the peak of the decarboxylation curve and start down the other side toward low THC and high CBN. As previously noted, we can finish the decarboxylation later.
Keeping the boundary layer removed:
The boundary layer is the layer of partially reacted resin and dilute solvent that forms on the surface of the resin after the initial aggressive dissolution by the solvent. The solvent at that point is dilute, as is the resin concentration, so that the reaction slows or grinds to a halt.
To keep the reaction operating at a reasonable rate, we need to periodically or continuously remove that boundary layer, and there are four methods that I will present here.
The first is to stir. Simply stir gently and thoroughly with a wooden spoon
The second is to shake. Simply shake a jar of glycerin and plant material by hand regularly. A paint shaker would also work for this application.
The third is to tumble. Placing the jar of glycerin and plant material in a rock or photo film tumbler will keep the boundaries fresh. It is an effective and gentle way to speed up the process.
The forth is vibration. Placing jar of glycerin and plant material in a vibratory cartridge case cleaner, or other form of vibration, creates more shear energy that tumbling and will dissolve the material the fastest of any method we have tried thus far.
Material selection and preparation for hot or cold processing:
While glycerin tincture can be made from anything from prime bud to stems, it is tastiest done from prime bud and least tasty with the stems. I usually make glycerin tincture out of the sweet trim removed from the buds during manicuring and popcorn buds.
It is not necessary to grind up the material, only to break it up any buds so that the material is loose enough for the glycerin to reach all the surfaces. Excessive pulverization of the material will result in color and particulate pickup that is difficult to remove. If you leave some surfaces blinded however, the resins on those surfaces won’t be removed either.
Extracting using the cold process:
The cold process is the easiest and tastiest way to make glycerin tincture. We extract using the cold process, simply by soaking the plant material in glycerin at ambient temperatures and agitating it for sixty days or more. Sixty days is about the least amount of time for a cold extraction, and typically they are run 90 to over 120 days. I have one experiment with more than 365 days of soak time.
After the extended soak and agitation, the glycerin is poured off and pressed out of the plant material to yield quality and tasty tinctures. It can also be used with fresh material for another cycle, so as to build up more potency.
There are a number of ways to press out the glycerin from the plant material, and it applies to both cold and hot extraction, so I will cover that in a separate discussion at the end of extraction methods.
The way that we make cold process glycerin tincture, is to load a canning jar 2/3’ds full of plant material, lightly compacted and then cover with glycerin while stirring with a wooden spoon, until every surface is well coated and mixture is homogenous, and then add another inch of glycerin on top.
We place the jars in a cool dark place or cover to exclude light. We sometimes wrap jars with aluminum foil to exclude light.
Every day for the soak period days, we periodically agitate the jars, using one of the above methods and at the end I filter out the plant material for a a light golden to dark amber glycerin tincture, that is tasty and of high quality.
Because the aromatic terpenoids are preserved, it will have many flavors present, interacting and darting off in all directions simultaneously.
You can more easily filter the mixture if you warm it up to 150F or so before filtering.
Potency and gleaning:
As previously noted, to reach maximum saturation, requires processing more than one batch of fresh material through the glycerin, because as the saturation level increases, the glycerin becomes less aggressive as a solvent and the remaining partially dissolved cannabis is also no longer at full strength and as reactive.
In point of fact, the fresh pressed material from the above first cycle will still contain significant cannabinoids, which takes two to three cycles to get it all.
What we do is put the fresh pressed plant material back in the jar and refill with fresh glycerin and add fresh material to the freshly pressed glycerin for another cycle, if I desire more strength.
The fresh glycerin will do the best job of scavenging the remaining cannabinoids, and then can be used again with fresh material to further build up its potency. It is by this cascading technique, that we can leave little behind and yet still maintain quality and potency.
I should note that the most potent glycerin tincture is not necessarily the most tasty, and one cycle produces effective meds, so most of the time we do not bother to bump up the potency with cold tincture.
Hot glycerin extraction:
We prepare plant material and extract cannabis by the hot glycerin extraction process in much the same way as we do by the cold process, though we stir it instead of shaking, tumbling, or vibrating it.
We also use a thermal cycling process and stir regularly, rather than an extended cook as many processes call for. The expansion and contraction of the thermal cycling help break up the resins so that they dissolve more readily.
As with cold tincture, we load a canning jar 2/3’ds full of plant material, lightly compacted and then cover with glycerin while stirring with a wooden spoon, until every surface is well coated and mixture is homogenous, and then add another inch of glycerin on top.
We then set that jar in an electric fondue pot full of hot Canola oil at 200F, and stir it regularly with a wooden spoon until the mixture reaches 180F, and then we adjust the pot temperature controls to maintain 180F.
We stir the mixture regularly with a wooden spoon, for another thirty minutes, and then take it out of the hot oil and allow it to cool to ambient temperature.
For what it’s worth, we use a wooden spoon, because a light tink with a metal spoon against a hot glass jar while stirring, can break it and dump the whole mixture into the hot oil.
After the mixture has cooled to room temperature, we again place into 200F oil and bring it back up to 180F while stirring regularly. When it reaches 180F, after a through stir, we take it out of the hot oil and let it cool to ambient temperature again.
We repeat the last step about five more times and after the last cook and stir; we filter out the plant material while the mixture is still hot.
Filtering glycerin tincture:
Vegetable glycerin is thick and syrupy, so it doesn’t filter quickly or easily without mechanical help. The simplest way to filter it is to heat it up so that it isn’t so viscous, and pour it into a jelly bag, which you wring out by hand. That works, but leaves a lot of glycerin behind and you are limited to temperatures that you can handle with your hands.
A French coffee press, a potato ricer, or a jelly press can also work, and you can buy tincture presses used by the botanical extraction industry.
We made my own press, using a hydraulic bottle jack inside a scrap metal frame, which presses a filter bag between two stainless dog dishes, at a force of 12,000 psi, and catches the glycerin in a third stainless dog dish.
It presses the plant material into a hard little puck, that we have to break up to reprocess.
Flavoring glycerin tincture:
A well made glycerin tincture is a taste delight in its own right, but for those of ya’ll who just like to play, here is how we’ve flavored glycerin that I had already infused with cannabis oil.
We started by adding equal parts of Bing Cherry and Blueberry raisins in a blender with enough 190 proof grain alcohol to make a soupy paste when macerated by the blender.
We tossed in half as much Japanese Gari and a dash of Almond extract, added another half a cup of 190 proof, and let it blend well.
When pureed, we poured it into a stainless mixing cup and placed it in a 180F hot oil bath. We cooked and stirred it until all the alcohol was gone, and then removed it to cool.
We then put a bout two tablespoons of that concentrate into each 1/2 pint of infused glycerin to be flavored and place it in the 180F oil to cook for thirty minutes while stirring regularly.
At that point we remove it from the oil, filter out the concentrate using a filter bag and the glycerin press. The glycerin is delightfully flavored, and the chef gets to eat the concentrate from the filter bag! Ahwooooooooooooooooooooooooooooooo!!!!!!!!!! Hee, hee, hee………………..
Hot soak for one week; Hot cycle 7 times;Cold vibrate; Hot cycle and vibrate
Cold Vibrate Density samples
Second pressing of material 160F cycled 7 times
Cold press 60 days Hot versus cold extraction