Cannabis Oil QWET Extraction Battle of the Wash: Dry Ice vs. Freezer


QWET cannabis oil extraction involves freezing cannabis and ethanol before combining them to “wash” and harvest the cannabinoids and terpenes from the cannabis plant to craft a concentrate containing the maximum amount of cannabinoids and terpens and minimum amount of undesirable components like fats, lipids, and chlorophyll. Once the combination of ethanol and cannabis has soaked for a predetermined amount of time it must be strained to separate the plant matter from the resulting ethanol solution we will now call the “wash”. The wash contains all the components that have been harvested from the cannabis plant and will later make up the final concentrate once the ethanol has been removed by forced evaporation.

Previously, I wrote a blog post “Super-Cooled QWET Wash for Cannabis Extraction Using Dry Ice” explaining the process when I was first experimenting with it and using badly beaten up trim with some good success. As soon as I finished that post I wanted to revisit the dry ice exercise to find out how far I could push the wash with better material and how it compared to simply using the freezer, so here we are with the follow up post and the epic Battle of the Wash: Dry Ice vs. Freezer!


There are many different methods of infusion and extraction, all with a different set of advantages and disadvantages. With QWET the solvent involved is food-grade 95% ethanol and it’s advantage is a high efficiency in collecting cannabinoids and terpenes. Unfortunately, that high efficiency of collection also extends to aggressively attaching to undesirable water based components like fats, lipids, and chlorophyll, ethanol’s only disadvantage. Fats, lipids and chlorophyll from the cannabis may be acceptable to varying degrees when making oil for edibles or medicinal full extract cannabis oil (FECO), but they are very undesirable for a high quality, clean, concentrates intended for smoking. Therefore, to craft a concentrate free from undesirable components the undesirable plant components must be neutralized by freezing and the alcohol must be super-cooled to keep them frozen during the wash. In simple terms, when the plant material is frozen and the ethanol temperature is below freezing the polar attraction of the ethanol and undesirables in the plant matter are unable to latch onto each other and the undesirables stay with the plant matter when the freezing ethanol is strained away, ideally leaving only terpenes and cannabinoids in the wash. You will know success when the resulting, well filtered, wash is a beautiful, crystal clear, light golden color with no trace of a green hue.

The difference between green on the left and gold on the right



For this battle my plan was to use high quality indoor dried buds to achieve nice, high yields. Unfortunately, the material I used ended up being quite crusty, not great quality, and contained quite a few seeds. Using lower quality buds may have actually been a blessing in disguise. In using lower quality buds I set the bar low for expected yields, knowing high quality dank will surpass it.

The goal in preparing the buds was to break them up as much as possible by hand to allow the ethanol to flow freely over all surfaces and at the same time cause as little damage as possible. Ripping, tearing, cutting, and trimming plant material causes cell wall damage and allows undesirables to flow unimpeded into the wash contaminating it and turning it green.


Pitting dry ice against the freezer required numerous runs of differing duration to collect enough data points and information for meaningful comparison. To this end I decided to do 3 runs in the freezer and 3 on dry ice. The washes would be 5 , 10, and 15 minutes long for the freezer compared to 15, 20, and 30 minutes on dry ice. Each run was allotted a ½ ounce (oz). After removing the seeds and stems, and breaking up the buds by hand, I ended up with 6 plastic bags containing 13 grams (g) each. The 6 happy bags parted ways with 3 going in the freezer for 24-hours and 3 in a cooler with dry ice for 2 hours. The ethanol was also split up, putting half in the freezer for 24-hours and half in the cooler with dry ice until it reached -30°F to  -40°F.

Once the materials were properly cooled and frozen it was go-time. The process was to take each bag of the frozen cannabis, pour enough chilled ethanol into that bag to allow for free movement of the material in the solution, and quickly return the bag to the freezer or the dry ice cooler from which it came to soak for the predetermined period.  For the 5-min wash I lightly agitated the it every 1-minute and for the longer washes I did the same every few minutes. When time was up I quickly separated the plant material from the wash using 2 wire mesh coffee filters with a 150 micron screen sandwiched in between. The fast, rough filtered wash was then put through the Buchner funnel filter a 2-3 times until it was crystal clear, then into a mason jar.fullsizeoutput_1539

To purge the ethanol and claim the oil I worked so diligently for I used the Source Turbo by ExtractCraft ( I used this tool for many reasons beginning with it’s the perfect size for this kind of single batch production. Secondly, because it works under vacuum and operates at around 100°F the terpenes will show little to no conversion and the color won’t be adulterated by the open atmosphere and higher temperatures giving me a true color comparison of what actually happened in the wash when inspecting at the final concentrate. Lastly, it’s going to save me a lot of money in ethanol because I will reclaim almost all of it for reuse.

Version 2

The oil produced in the Source was then lined up on silicone mats in order of extraction duration and grouped together with the freezer and dry ice samples together. Finally, the oil was placed in a vacuum oven for post process purging to make the final product into shatter and ready for comparison.



My expectation for the freezer washes was that as the soak time lengthened I would see more and more green with the 5-min wash looking good and the 15-min wash looking glaringly green. I was shocked and very pleased to see the 15-min wash come out nearly the same color as the 5-min wash. There was only a slight difference between the 5 and 15-min while virtually no difference between the 10 and 15-min wash.

From left to right: 5, 10, 15 minute freezer washes

Once the final product was finished purging in the vacuum oven it was apparent that the color of the shortest wash was only slightly lighter than the longest, but not by much.  The final products were quite consistent in color for all three samples with the shortest wash showing only a marginal advantage with lighter color.   The yields of the three washes from shortest to longest were 12.5%, 15%, 15%.

Oil from freezer washes before final purge. Top to bottom: 5, 10, 15 min washes
Freezer wash final product.  Top to bottom: 5, 10, 15 min washes


The shortest dry ice wash was 15-min so I could directly compare a freezer and dry ice run of the same duration, then followed with the 20 and 30-min washes. Again, by the time I got to the 30-min wash I was definitely expecting to see obvious signs of green in the wash, but again I was happily surprised to see almost no difference in color between the shortest and longest soaks.

From left to right: freezer 5, 10, 15 min washes then dry ice 15, 20, 30 min washes

All three final purged products came out very similar with the shortest soak again showing only a marginal advantage in quality while the 30-min soak still looked amazing.  The yields from shortest to longest were 11.5%, 14%, 15.5%

Oil from dry ice washes before final purge. Top to bottom: 15, 20, 30 min washes
Dry ice wash final product.  Top to bottom: 15, 20, 30 min washes

Emboldened by the beauty of the 30-min wash success I was determined to find the limit and see where the undesirables would finally make their way into my wash and contaminate it with the green leak. I decided to perform a 1-hour dry ice wash in the same manner as the others. Again, a beautiful wash resulted and the final product looked nearly identical to the 30-min wash and yielded 16%. I was quite shocked again.



The shorter washes in each group were more clear than the longer ones which is commonly expected. The unexpected was the very narrow margin of clarity and color quality of the finished concentrates between the shortest and longest washes of each group.

I believe three factors made the very clean, long washes possible. First, the material, while broken up thoroughly by hand suffered only minor cell wall disruption keeping the undesirables well contained. Second, through the entire wash cycle of each run everything was kept well chilled and not allowed the chance to warm or vary in temperature. Third, the alcohol and plant material was separated with great expediency, and never squeezed nor pressed.

In general, the yields of both groups increased with longer soak times as expected. The 10 and 15-min washes from the freezer were identical, both 1.96 grams. I think the 15-min wash would have actually been a bit more if I had been more disciplined and consistent with the amount of alcohol used with every wash. It is clear in the photos that the 15-min freezer wash was 2 fl oz short of the other samples. I believe this reduced the final yield of that wash to some extent, but how much I don’t know. The dry ice samples showed an increase in yield all the way to the 1-hour mark but increased at a slower rate between the 30-min and 1-hour washes. I’m convinced the yields in this experiment were low due to the quality of bud used and can be improved with higher quality buds.

The stark difference between the freezer and dry ice runs, in terms of clarity and color, clearly demonstrated that the lower temperature of the dry ice QWET very effectively immobilizes undesirables and increases color quality. I think using the dry ice performs two processes at the same time. Normally QWET is done in the freezer, then to clean up further the wash can be put back in the freezer to winterize. Using dry ice essentially performs both of these tasks at the same time.

Freezer group on top, then dry ice group in middle, and bottom is the 1-hour dry ice run.

Playing devils advocate and a brief word of caution. Many people associate winterization, with some loss of flavor pointing to a possible loss of some terpenes and/or flavonoids in the process. If the dry ice QWET does simulate winterization then this loss of flavor could happen here as well. Therefore, I would encourage those that try this to experiment with both the freezer and the dry ice, using smaller quantities and exploring which method and soak time suits your personal preference. There is no right or wrong in this craft, it’s only what makes you happy and your friends pass out. Whatever you choose, crafting with the Source by ExtractCraft is going to help you make FIRE with ease and win bragging rights!


Troy and Colby, thank you very much for all your help and support putting this together, you guys are the best!

10 thoughts on “Cannabis Oil QWET Extraction Battle of the Wash: Dry Ice vs. Freezer

  1. In my own experiment, I found that not only was the color brighter doing the dry ice method, it had more flavor from terpenes. Dry ice imho, is superior to freezer method. Thank you for your excellent review

    Liked by 1 person

  2. Great article, keep them coming! You mention a vacuum oven. Is this only for make dabs? Or does it have other uses? Can you recommend a product that works for this process.


    1. The vacuum oven, also known as a ‘drying oven’ is a standard piece of lab equipment used for de-gasing. For concentrates it’s used to remove residual contamination like butane, water, and ethanol. They are quite expensive and the pumps you need to run them are quite expensive as well. If you are just doing small batches for fun a simple single stage 3 CFM pump and 1.5g tank with a controlled heater is fine. You can find a package deal on Amazon usually with all of that together for $200-$300. The most common brand used is Best Value Vac


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