Are you ready to kick your oil infusion skills up a notch? An alcohol intermediary oil infusion harnessing the solvent powers of alcohol might sound a bit intimidating, but it’s surprisingly simple to do.
Before we get to the hows of making an alcohol intermediary oil infusion, let’s take a quick look into the whys.
First, some essential resources
Creating an effective herbal infusion depends on matching your herb’s constituents with their preferred solvent(s). In chemistry, like dissolves like, so it’s useful to know a little about solvent polarity and the corresponding polarity of different plant constituents. But when you’re working with a whole herb, you’ve got something a lot more complex and synergistic than a simple isolated constituent, so these concepts become generalities rather than hard-fast rules.
Fortunately, there’s a whole lotta of resources out there that can help you to figure out which solvents are most effective at extracting what constituent – without revisiting your sophomore year chemistry class.
It’s essential to have trusted source (or two) for determining the specific phytochemicals in the herbs you’re working with. I bounce back and forth between David Hoffman’s Medical Herbalism: The Science Principles and Practices Of Herbal Medicine and Kerry Bone’s Principles and Practice of Phytotherapy: Modern Herbal Medicine. Both books contain extensive, detailed herbal monographs, including a list of primary constituents for each herb. If I can’t find an herb in one book, I’ll almost certainly find it in the other.
Now that we know the primary phytochemicals in our herb, which solvent(s) are best to pull them out? Richo Cech has a helpful section in chapter 5 of his book Making Plant Medicine, “Solubility Factors” that covers some major categories of constituents such as alkaloids, volatile (essential) oils, polysaccharides, resins, etc., examples of herbs that contain them, and what solvents will best extract these constituents. There’s also an extensive chapter on Solvents and which constituents they affect in James Green’s The Herbal Medicine Maker’s Handbook.
For the more advanced herbalist, if you really want to geek out on the chemistry of herbal constituents, Lisa Ganora’s Herbal Constituents: Foundations of Phytochemistry is a goldmine of information. While it’s a good mix of conversational and technical writing, be warned that this is a chemistry text book and is definitely not light reading.
For even more happy geek time, check out this fabulous solubility flowchart that illustrates what solvents extract which plant constituents, adapted from Lisa Ganora’s book and The Modern Herbal Dispensatory by Thomas Easley and Steven Horne and The Herbal Medicine-Maker’s Handbook by James Green.
I just wish I knew who created the flowchart. If anyone knows, please let me know in the comments so I can give them credit!
Solvents & solubility
When you infuse an herb in oil, it will draw out some the oil-soluble bits such as gums and resins, some of the volatile oils, certain oil-soluble vitamins (A, D, E, K), plant sterols and terpenes (oil-soluble carotenoids give plants their orange or yellow pigment).
A vibrant red (fresh) St. John’s wort-infused jojoba oil:
Compared to alcohol, water and vinegar, though, oil is a relatively weak solvent. Adding a bit of alcohol to the process will free more of a plant’s alkaloids, resins, flavonoids, glycosides, terpenes, and volatile oils, camphors and vitamins. Alcohol also tends to do a better job of capturing certain plant pigments. Chlorophyll, for example, is captured quite well by ethyl alcohol, giving your infused oil a more vibrant color vs. one made without the alcohol intermediary step.
So to draw out a more complete array of constituents in an oil maceration, ethyl alcohol can be used to do a quick pre-infusion before covering the herbs in oil. This added step draws out the alcohol soluble constituents in addition to the oil soluble ones, effectively increasing your infused oil’s potency.
Simply place your dried herbs in the vessel you’re going to use for the oil infusion. If the herb is in larger chunks, grind or crush into smaller bits using a coffee grinder or mortar and pestle. Barely moisten the herbs with a shallow layer of high-proof grain alcohol (the highest you can find, preferably 190 proof *). An easy way to evenly moisten the herbs without drenching them is to place your alcohol in a clean spray bottle and mist the herbs until moist. Loosely cover the jar/vessel with a lid or use a rubber band to secure a scrap of cheesecloth, and allow the herbs and alcohol do its thing overnight.
In the morning, most of the alcohol will have evaporated, and you can proceed with a normal oil infusion. The alcohol intermediary method benefits from a heated oil infusion method, because the heat will ensure that the last bits of alcohol and water evaporate out. This is particularly true if you used a lower proof alcohol. 151-proof Everclear is about 75% alcohol, which means the remaining 25% is water, and you really don’t want water in your final oil maceration. Remember to leave the lid off or vented during the heated infusion to allow for evaporation of any remaining moisture from your alcohol or herb.
If you only used a small amount of 190 proof (95% alcohol : 5% water) and you’d rather do a warm or solar infusion, that’s okay too. The teensy amount of water left in the infusion should not be significant.
In addition to the added potency, an alcohol intermediary infusion should also improve your infused oil’s shelf life. There will be no appreciable alcohol content left in the oil once the oil maceration is complete, but the extra alcohol step reduces the microbes introduced into the oil. Remember to label your jar with the herb, type of oil used and date (a note about it being an intermediary infusion might also be useful) and store in a dark, climate controlled location. It should last well beyond the estimated 2-year lifespan of a regular dried herb-infused oil.
* We can’t buy 190-proof anything here in Idaho, but I’m fortunate that we live within a pretty easy drive to the Washington border, where 190-proof spirits are a thing. Each time I pick up a few bottles of 190-proof Everclear, I always feel compelled to make sure the checkout clerk understands that I’m NOT drinking it, I swear! I’m not that kind of an alcoholic thankyouverymuch… I’m TINCTURING! ♥
Thank you for this!! I was wondering if you leave the cover off or on during the heated oil infusion? My plan was to place the in my dehydrator at a temp between 100-105 F and wasn’t sure. Thanks I’m advance for any further imparted knowledge🌻
Hi Stefanie! Yes, when doing a heated oil infusion, definitely leave the cover off (or at least vented) to allow evaporation of any remaining moisture in the alcohol or herbs. Your intuition is spot on! Using a dehydrator is a great idea too. 100-105 F is a good range for preserving the quality of the herbs and preventing them from overheating or burning.
I’m looking at making a marijuana infused oil using this method but only have access to 40% alcohol. Question 1… do I still need to decarb the herbs and question 2. Will there be too muvh water from the 40% alcohol or will I manage to burn this off if I heat it in a slow cooker or rice cooler. I’m worried the water content may reduce the shelf life of my balms. I’d appreciate any suggestions. Thanks
Hi Linda! I don’t have any direct experience working with THC (since it’s not legal in my state) but my understanding is that you can decarb the herb at the same time it’s infusing in oil – the decarboxylation process will just take a bit longer, since oil acts as a buffer and can slow down the conversion of THCA to THC. Ideally, you’d want to use a high-proof alcohol, such as Everclear for your intermediary oil infusion to better extract the resinous compounds and minimize the water content in your balm, but you may be able to get away with using 40% alcohol if you heat the oil infusion low and slow for a longer period of time to evaporate the water content (which you would be doing anyway for the decarbing process). Be sure to leave the lid off your slow cooker to allow the water to escape. Good luck!
I have the same problem as above, access to approx 75% alcohol
I fail to logically see how water can evaporate at such a low temperature. Can’t water only evaporate at 100 degrees Celsius?
Will the water actually evaporate slow boiling at lower temps?
Hi Davy! While it’s true that water’s boiling point is 100C (212F), evaporation can occur at lower temperatures. Water molecules can escape from the liquid phase and enter the air as vapor at room temperature, although the rate of evaporation will be much slower than when heat is applied. Low heat (that won’t denature your herb) will speed up this process.