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

By Troy Ivan


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. 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

The concentrate can be created at low temps around 100 F and ethanol recovered for reuse using my DIY system that’s inexpensive, very fast and extremely reliable. The oil produced 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 devil’s 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!


IMPORTANT NOTE: I used ExtractCraft mats in this post but I would not recommend their equipment under any circumstances.




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

  1. How much do you break apart the buds? You have mentioned not breaking them up too much if you are avoiding green wash.

    1. Not really. It depends on the quality of the material, the process you use, what you are making, and how many times you wash the material. Yield can range from 5%-30%

  2. How would you use the source to make a tincture with bourbon for sublingual dosing.
    I’m using 100% ETOH which is too hot by itself!

      1. I over did it once (turned into goop) and it would not go into solution with bourbon. But I’ll try again and let you know.

  3. Have you ever done dry ice QWET with fresh frozen cannabis, as in the buds are removed from the plant and frozen immediately after harvesting without any drying? I have read freezing fresh maximizes terpene retention, so I wonder if combining that with your dry ice QWET could make a very flavorful CO extract. I would think that as long as the buds stay frozen during washes due to the dry ice that the water will remain locked up in the bud. Even if some did come out in the ethanol, do you think that would cause any problems downstream?

    1. too much water content. You can do if you use a freeze dryer with the fresh material first.

  4. Hey! New at extractions! Using the source and dry ice to produce feco for edible or even better sublingual use! Your site has been most helpful and I am so greatful for your effort to educate us novices! So let me ask: i have used your insight to create concentrate tincture using the source but the sting of the ethanol is still killing me, even with the lowest possible dosage! So is there any way i can get sublingual absorbing of my feco, without the ethanol taste and sting? Thanks in advance…

    1. Hi. I’m glad this information has been helpful. Unfortunately thats the problem with ethanol, it’s very aggressive and burns. You could try to add some water. You could put in an alcohol safe spray bottle and spray in the mouth? Otherwise just add the extraction to a carrier oil and use more like an edible?

    2. I found with tinctures at least if i use terpenes the ethanol taste is reduced if not eliminated!

  5. Thanks for all the great info it has helped tremendously. Do find the Qwet method is the best way for making feco for edibles? And lastly do you think it’s worth doing a second wash when you soak for a longer amount of time.

    1. Yes, QWET for edibles is best in my opinion. I’ve commented a bit about it in the “Cooking With Concentrates” post as well. A second wash viability would depend on quality of material and efficiency of your wash, so it depends. If you have very high quality material and you did a really cold and quite short wash, then a second wash would probably collect quite a bit (I never combine washes). If the material is marginal and you were quite aggressive with the first pass then maybe not.

  6. Hi there,

    I ground up my backyard bud in Coffee grinder, decarboxylated in oven, froze ground flower and ethanol , then combined for 24 hours, my wash is quite dark even after running it through Buchner flask w thru 3 micron paper filter w/ 1/4″ of activated charcoal powder on top.
    ran through Turbo extractor to concentrate. still fairly liquid and dark, if I do a dry ice “settle out” would that clear up a bit more? or better to try Buchner w DE? using for tincture

    1. If you don’t want it dark don’t grind and watch the exposure time. EVERYTHING in you question is answered in the post you commented on I believe

    2. You used a paper filter and AC in a Buchner? Was it fritted? AC works best in a fritted Buchner with a 1/4″ DE bed.

      1. Sometimes you work with what’s best and other times you work with what you have.

      1. I would filter first so 1) the carbon isn’t wasting time on plant matter that will be filtered out 2) it doesn’t make primary filtration heavier and more difficult

  7. Hi Mate, just about to extract some feco for a cancer patient. Have just purchased the Buchner funnel vacuum flask 1L with 0.45 micron nylon membrane filters will be using iso as the solvent. at which micron can i filter to achieve the best results without removing the needed components. Have as low as 20 micron coffee filters and no in between at this stage. I Appreciate the knowledge. Cheers.

    1. I use 3 micron slow flow filters. I’ve never seen 0.45 micron nylon filters, do you have a link so I can look?

      1. Probably too late unless you want to try scrubbing. You can see the details on that in my “Polishing Dark Extracts” post. If you don’t want those green and planty components in your extract its best to avoid them from the beginning of the extract for best results.

      2. My plants were processed by a company and came back as a very thick sticky oil ..only way to transfer is lightly warm..I would like to take to clear..and not destroy thc

      3. Sounds like your expectations are outside of realistic process and extraction components. You may need to do some studying on the topic of extraction and what the final form of extractions look and handle like.

  8. I put bud and ethanol in freezer. I use my first wash for vape concentrate. I keep the jars of washed buds in the freezer and later rewash the same material; this second wash I extract and decarb and use for sublingual or patches. I’ve also done this a third time. How will I know how many times I can do this to the same material? And how long can I store this material in the freezer in between these washes? I’ve been determining my time frame based on my daughter’s need for the various medications. (Also, just by my nature, I hate to throw anything out that may still have some value, even though I have a fairly plentiful supply!)
    I’m not sure where to ask this question and my searches on the FB page don’t come up with the answer.
    I’m also beginning to think I should do these washes as close together as possible and then store the wash (keep it in the freezer) until I can get time to process it in the Source. Then once it is extracted and air purged I guess I should collect these little batches from the Source until there is enough to make the medicine in larger batches. (Until now I’ve been using the small quantities each time just as she needs more vape, or sublingual or patches.)
    I’m just wondering if a) my process is making a less effective medicine either because I wash it too often, and/or wait too long between washes, and b) if my process can in some way be made more efficient.
    My daughter continues to say the medicine works even on the third wash cycle. I’m not using it myself so I can’t make my own judgement on the quality…but love the plant and the smell and very occasionally smoke a little. My harvest seems to have cured well and have a long shelf life! (That’s what I have tested for myself, using product from summer 2018 harvest. So growing every other year is good.)
    Thank you so much for all you share and and teach AND for helping me figure out how to make medicine for my daughter.

    1. It’s all about the efficiency of what you are after, I would recommend reading my post on Yield and Extraction and the balance of the two. That is what it basically comes down to. If you are planning on doing more than one wash I would do them back to back, you can always store the wash instead of storing the material.

  9. Thanks for the great info.
    Did I miss in the post where you said how cold your freezer is?
    I only ask because my stand alone freezer gets down to 0°f and I was wondering how long of a wash I could get away with at that temp? My end goal is a wax that I could dab.

  10. Thank you for your fantastic treatise!! I’ve learned a LOT.

    I’ve been told I’ll damage my vacuum pump if I use it to remove the ethanol from extract. How do you avoid this? How do you recover the ethanol? I’m familiar with using a condenser when evaporating ethanol with heat, but I’m unaware of how I would recover it when removed by vacuum.

    1. I assume you mean purging in post processing terms and not primarily ethanol recovery. It kind of depends on volume. If you are post process purging 1g at a time in a 1 gallon tank you aren’t going to pull much. If you are doing many grams and have the pump pulling the whole time you will catch more ethanol vapor into the pump. To avoid you can get a cold trap

  11. Maybe stupid question, but cant find answers… Can i use wheel filter? or are there any other options for good filtering? Or could i just buy 5micron pp filter and use it without buchnel funnel (i dont care about time)?

    1. Any filtration method that’s is food safe and doesn’t introduce chemicals nor contamination works

  12. “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”
    What size Büchner funnel? 120?

    1. I should also add, I am now just laying a larger 40u or 80u mesh over a kitchen strainer.

  13. Dear IchibanCrafter,

    I have been reading your blog and soaking up all the information.
    This takes money, time and effort.
    Thank you so much for doing this and sharing this wealth of knowledge!

    I am reading everything and would like to make vape cartridges, and following all your procedures and tips.
    I don’t own an extractor and/or vacuum yet, just reading for now 🙂

    Just a quick question on the QWET.
    Where do you purchase your Ethanol and are there different “brands” you prefer?
    I do have 190 proof Everclear that is 95% ABV.
    Can I use that as wash liquid?
    I have heard different opinions about Everclear.
    Any thoughts?


  14. I was wondering if it would work to put some of the dry ice directly into the cold Alcohol before doing the wash.

    1. People often want to do that but it’s not as good of an idea in reality as it is on paper. Forcing C02 into the wash, uncontrollable bubbling action, and undesirable contamination are just a few reasons why it’s not really a great idea.

  15. Thanks for your reply and also thanks for this excellent Blog.

    I was thinking that I would wait until after the bubbling had ended to use the alcohol to do the wash but I did not know that there might be a possibility for contamination from the dry ice so I will skip that idea and use your procedure. This is my first attempt and I only have 15 gm of dried & cured small buds that I will be using.

    My objective is to make RSO/FECO with Everclear but I don’t want the end product to be full strength so after the wash I was going to boil off only ~ 90% of the Everclear. After that I was thinking that I would like to add in an equal amount of Olive Oil or MCT oil for palateability and to achieve my desired dilution. Can I add the oil right at the end of my boiling and will it combine fully and not separate out? Which oil would you choose to do that? I do have a heated stirrer to use for that step.

  16. No I had not read that article yet. Thanks for pointing it out to me. I definitely want to make the “clean Golden Tincture” version to cut down on chlorophyll and I was hoping for sub-lingual absorption. From reading your article I learned that once it’s combined with an oil carrier sub-lingual is out the window so I guess my best bet is just boil off most of the alcohol and go with that. If it burns too much then I can cross that bridge when I must. Thanks again for your help. MUCH appreciated.

    1. I think it is best to accept the fact that using the carrier oil takes a little longer than sublingual. I actually am not a huge fan of the sublinguals, defiantly feel like better and more full results with the oral ingestion with the oil and some say even more so by adding some sunflower lecithin.

  17. Hi Ichiban,

    First, thanks for your info. It’s been invaluable and so refreshing to have a reference that isn’t mostly or partially full of $%^&* like so many other sites.

    I’m a proud Source Turbo owner and have made a few dozen cannabis tinctures so far. My goal is maximum yield in as few washes as possible, and I’ve been having good success with extreme agitation of decarbed flower in Everclear at room temperature using a magnetic stirrer. I limit the amount of flower to 7g and use around 150ml of Everclear in a mason jar. As the end purpose is for ingestion and not vaping, I don’t mind extra ‘stuff’ in it. After stirring the wash and flower, I have been removing the flower and putting the resulting wash in the freezer for several days, and then performing more filtering before putting it in the source turbo using a few coffee filters. The final product is then put in a tincture and ingested. I’ve recently purchased the Buchner setup but haven’t had a chance to use it yet.

    With that said, it’s gone quite well. My complaints are few, but the perfectionist in me needs to address them.

    1) As I reduce the final product in the source turbo more and more, I’m running into problems with ‘gunk’ at the tail end of using the tincture. As I measure the potency in drops (often two drops will be plenty for a single administration), even a little gunk in the dropper confuses my estimates of potency (and thus of dosing) in the last dozen or so drops. Getting rid of this final gunk would be awesome.

    2) I’d also like to reduce the time it takes to cool down (3 days in a household freezer seems to work best) before filtering. If I can even get it colder and help the filters better do their job, all the better!

    As the cold from dry ice would presumably really reduce the yields I’m used to and require a bunch more washes, I’m not sold on using dry ice in solution with the flower. But using dry ice in solution after flower removal, and pre-winterization, just to get it really, really, cold quickly, sounds like a good idea at the moment. I’m very tempted to plop some dry ice in the mason jar, leave the lid off and use that to cool things down before filtering.

    In the comments above you mentioned that CO2 and agitation would be an issue for putting dry ice directly in solution with the flower, but this situation seems different as the flower isn’t present?

    Good idea, or is there a problem / better way? Does getting it as cold as possible greatly assist with filtering? Who knows, maybe I’ll start using the Buchner with my old method and not need to care?


    1. 1) The gunk comes from soaking too long and/or too warm. You said “I don’t mind extra stuff in it.” That gunk is your extra stuff. If you don’t want it in there then avoid picking it up when making the wash. Maybe checkout my post “Ethanol Extraction: Complete Breakdown” for lots of tips.

      2) Checkout the post I mentioned above, that should help. Putting dry ice into the wash is a bad idea, don’t do it. All beginners think this is a good idea, if it were then that is how I would be doing it in the articles here.

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