Making a great smokeable cannabis concentrate yourself at home, with good color, great taste, and unbelievable potency is easy but you must understand some basic fundamentals of how to keep the green out of the extraction. Using ethanol for cannabis extraction is very effective, but has limitations due to its hydrophilic and polar nature. Meaning it likes to pick up polar and water based molecules and that’s not good for cannabis extraction. We don’t want polar, water based undesirables like chlorophyll, waxes, paraffin and fats in our extractions so we must take steps to limit the contamination. To limit the uptake of undesirables we use a method called Quick Wash Ethanol (QWET). QWET involves freezing ethanol and cannabis separately before the extraction, controlling the duration the cannabis is exposed to ethanol in the wash, stopping it from turning green and instead producing a beautiful golden wash and amazing concentrate. In this blog I introduce the use of dry ice to super-cool and increase the effectiveness of the process and take QWET to the next level.
WHY FREEZE FOR THE WASH?
Performing a wash with ethanol and cannabis at room temperature allows the ethanol to quickly attach to polar undesirables in the cannabis and carry them into your extraction turning it green and unsuitable for making a quality vapable concentrate. To avoid picking up undesirables in the wash, freeze the ethanol and cannabis separately overnight. Freezing cannabis immobilizes water based compounds making them difficult to pick up. Freezing ethanol also helps in two additional ways. First, it keeps the cannabis frozen during the wash cycle. Second, when ethanol is lowered to below freezing temperatures it’s pickup of soluble components is substantially slowed and the ability to attach to frozen water based components nearly eliminated. This is very useful because to make the best smokeable concentrate we have to eliminate undesirables and maximize the pick up of the soluble components we want like THC, CBD and terpenes.
Using a freezer to perform frozen QWET works with the general limitations of 10-min wash for flower and no more than 3-min for beat up trim. If executed with care, using quality buds broken up by hand with minimal cell wall damage it can be stretched to 20-minutes. For best results it’s very important to keep everything frozen the entire time and gently shake the mixture periodically to make sure a saturated boundary layer doesn’t form around the plant material.
There are two situations where this process has weaknesses. First, using beat up, chopped up trim with a lot of cell wall destruction still tends to leak green and quickly pick up a plant flavor. Bad trim can leak in as short as a 1-minute wash. Second, the temperature of a typical freezer will not keep the water elements immobile very long and will warm quickly once removed from the frozen environment. Dry ice can combat these weaknesses to enhance the immobilization of undesirables and slow pickup further.
COOLING WITH DRY ICE
The average recommended temperature setting for a freezer is 0°F compared to the surface temperature of dry ice being nearly -110°F. That large difference in temperature give us the margin necessary to hit the recommended wash temperature of -40°F, substantially colder than a freezer’s ability, providing absolute immobilization of water compounds and slowing pick-up to a crawl.
To use the dry ice method here is what you will need:
- Ethanol – 190-proof (95%)
- Small cooler
- 2 ziplock freezer bags
- 2-4 lbs of dry ice.
Place the cannabis in one ziplock and ethanol in the other. Put the dry ice, cannabis and ethanol into a small cooler. Restricting the amount of open space in the cooler will help with cooling. It should take about 1-hour to sufficiently freeze the cannabis and cool the ethanol to -40°F.
When the cannabis and ethanol are suitably cooled combine them and keep the mixture in the dry ice environment for the duration of the wash. You must gently agitate the mixture every couple of minutes to move saturated ethanol away from the plant material and fresh ethanol in. If you’re using beat up trim use very light agitation only, but with quality flower a little stronger agitation is beneficial. Once the wash is finished continue with filtering, evaporation, and post processing as you normally would.
-Dry ice wash using poor quality choppy trim-
To test the dry ice wash tolerance for poor quality choppy trim I tested the difference between 3-min and 10-min washes. I like using inferior materials for process testing because it clearly gives the worst case scenario.
Both wash samples came from equal amounts of ethanol and 29g of poor quality Jack Frost trim. For separation and filtering I used a Buchner funnel under vacuum to separate the cannabis and ethanol as quickly as possible to minimize the risk of green leak. Both samples in the photo were approximately 10 fl oz with the lighter 3-min wash on the left and darker 10-min wash on the right. There’s an obvious color difference between the wash on the left and the one on the right.
After evaporating the alcohol at 102°f for about 3 hours using the Source by ExtractCraft the oil from both samples looked remarkably similar in every way except volume. The 10-min wash produced more volume and appeared to be of the same nature and characteristics as the 3-min wash with no apparent additional pick up of undesirables. That means the the difference in the washes was not a simple color difference but due to increased density of desirable component pickup.
Lastly, the oil was purged using a standard vacuum chamber and single stage pump operating between 90°F-100°F for 72 hours ending with very interesting results.
Both samples appeared identical in quality but weight was clearly a different story. Fully purged the 3-min wash sample was 0.9g and the 10-min wash sample came in at 1.4g, more than a 50% increase (yields are low as a consequence of using scrappy starting material). The 50% gain came with no discernible detrimental effects of the significantly longer super-cooled wash.
-Dry ice wash using quality flower-
Using flower provides some distinct advantages. Flower has the best trichomes in the most concentrated areas and these are what we’re obviously most interested in targeting. Also, the layered fashion in which the buds grow make it easy to break up by hand without causing much cell wall damage and protecting the extraction from green leak. Breaking up buds by hand (don’t grind) is important to allow the ethanol access all surfaces and flow freely over the cannabis during the wash. Compared to trim, flower can definitely stand up to extended ethanol exposure and slightly more robust agitation, both of which are instrumental in harvesting as much THC, CBD, and terpenes as possible.
For this experiment I used 14g of Bubba-Cross flower for each wash. Knowing flower can stand up to more aggressive treatment in the wash I started testing with a 15-min wash, and it came out beautifully. I then stretched it to 20-min, then 30-min then 1-hour. I was amazed the wash could be stretched to an hour, and could have easily gone even longer, but most importantly all the washes maintained the same color characteristics! The color characteristics are uniform however the density of pickup clearly increased with the longer washes (left to right: 15 min, 20 min, 30 min).
To process the extractions I used the Source Turbo by ExtractCraft (www.extractcraft.com) to make the strongest oil possible then finished in a vacuum oven at 90°F. In the photos below you can see the result of the 1-hour wash. On the left is the oil straight out of the Source Turbo and on the right is the finished purged product. That’s from a 1-HOUR WASH Y’ALL!
In terms of quality and yield it’s the same observation we had with the choppy trim results. Quality didn’t suffer in any real observable way but the yield increased tremendously. The yields from the 15-minute wash to the 30-minute wash increased from 11.5% to 15.5% providing a 35% increase in yield for the exact same material. The 1-hour wash showed a small increase in yield at 16% but the gains in yield seemed to be slowing.
CONSIDERATIONS AND TAKE AWAY
Dry ice definitely makes cleaner QWET extraction possible and almost easy. The low temperatures used with a dry ice wash defiantly slows the absorption and collection of the desirable components as well as the undesirables. Some people contend that when using dry ice to wash good flower it loses some flavor and terpene profile. I don’t know to what extent this is true because I don’t have testing lab access, but to my experience I think it holds some merit. Dry ice extraction compared directly with freezer extraction from the same material has shown me a small decrease in flavor, but no apparent change in potency. Conversely, freezer QWET will sometimes have a slight plant taste while a good dry ice QWET never does. With everything we covered in mind, I think the take away is with trim absolutely use dry ice to make good trim into amazing smoke, decent trim into something very good, and throw away trim into something useful and valuable. With flower it’s debatable and you are going to have to experiment and try on your own to determine what is best for you because we all have very different preferences.
I have another blog that ties into this one that pits using the freezer against dry ice and compares the results. If you’d like you can check it out here Cannabis Oil QWET Extraction Battle of The Wash: Dry Ice vs. Freezer
- “Super-Cooled” isn’t technically correct as far as science is concerned but it sounds so super-cool that I couldn’t resist taking some literary liberties and bending it to my own demanding cannabis needs.
- I’m no expert and still learning, so if you see something blatantly wrong or silly please point it out.