Winterization and Filtration of cannabis extracts

Why Winterize?

Proper winterization is an important step in creating a high purity extract.

Winterization is the removal of lipids from crude extract. Lipids are fatty acids that are also extracted from the plant. It is typically the next step after extraction.

Why winterize to remove lipids?

  • Fats dilute the cannabinoid fraction, lowering the purity
  • Fats can cause distillate to be less transparent hurting its value.
  • In vape pens, they can burn on the coil and cause the pen to taste burnt.

The amount of fats picked up in the oil during extraction vary according to the extraction method used.

Waxes removed by filtration
Waxes on the filter


How Extraction Impacts Winterization

Cold ethanol is the best extraction method for minimizing fats in extract. The colder the ethanol, the less fat will be pulled from the plant.

BHO extraction picks up a moderate amount of fats. Think of the cloudiness that can be seen in shatter or a similar product.

COextraction is known for pulling the most fats out of the plant.


Even between those three methods, variation of the extraction parameters has a strong influence the amount of plant fats picked up.

Winterized versus unwinterized crude
Winterized crude on the left and unwinterized crude on the right.

General Winterization Techniques

Typical winterization:
  • Using 10 Liters of ethanol for every Liter of crude extract
  • 190 proof ethanol is actually preferred to pure ethanol. While also being cheaper, 95% ethanol has 5% water making it ever so slightly more polar. This is beneficial for winterization because the cannabinoids remain soluble even at cold temperatures whereas the waxes are insoluble and crash out of solution.
  • Get as close to -80 C as possible. Above -20 C, winterization will do very little. People use chillers, walk in freezers, chest freezers, dry ice, etc.
  • 24 hours or more is a normal time to wait for waxes to precipitate out. Shorter times can be used, but it is not as thorough.
  • To see if any waxes remain in the filtered solution, you should place a small sample (several mL) back in the freezer for a day or so. If the solution appears cloudy when you check back up on it, further winterization may be needed.


Typical Filtration:
  • Vacuum/pressure assisted filtration
  • Highest surface area filter possible
  • If possible, scrape accumulated waxes off the filter (without disturbing it!) because they will lower the flow.
  • Use several different filters. For example, start at a higher micron filter, use a medium filter, and then finally task your smallest micron filter with only the finest particles of wax and the least amount of waxes.
  • Metal filters can be expensive compared to paper filters, but they are reusable and they can’t rip.







If you are using filter papers:
  •  That there are NO gaps between the edge of the paper and the filter
  • Cover all holes completely
  • Consider using either a gasket and clamp to hold the filter in place or use a filter bed. Both of these things will prevent the filter from shifting, prevent solution from going around the edge, and allow you to scrape waxes off the filter to improve time efficiency.


The fats removed by winterization will add up to several percent of crude extract.


Ethanol used for extraction and winterization is an excellent candidate to be recycled for reuse with a B/R distillation system.


  1. Hello!

    I am just curious if the waxes and lipids filtered out could be used for something else, such as a salve or lotion?

    Thank you


    1. Hi,

      I have heard that before. I don’t know how the process works though. You may want to rinse the filtered fats and waxes first. Maybe I’m wrong and the other compounds present could be beneficial.


    2. Very good! I love eatting crude and it’s been very helpful with pain and sleep


    3. I have been playing around with that and it can be done. You just have to practice


  2. Could ypu make candles out of the waxes? Lol


    1. If you get creative enough!


  3. What micron size for ea filtration


    1. Hello,

      I would recommend starting at ~20 micron to remove the bulkier waxes and then moving down to as low as possible. Maybe 20, 10, 5 micron for example. If you choose to go to the smallest micron immediately, your flow rates will suffer greatly as the larger waxes will clog the pores of the filter very quickly.



      1. Buen día, ofrecen capacitación, soy de Mexico, estudiante de la UNAM


  4. Luke,
    Have you actually developed a working process with the exact equipment needed to winterize CBD? Reason I’m asking is I have a licensed lab and we are getting in CBD for drug applications. I thought it would be a great idea to winterize this that we have and produce enough pure, safe oil for vaping pens. I could use the collaboration, thanks.


      1. Micheal, are you still available to help with winterization? We are in Eugene, Oregon and I need some crude winterized.


  5. Question I’ve been winterizing oils for years and never have I came across when in the process the whole liquid looks like caramel colored solution like it normally does, but there has been no separation and its now going on 40hrs. I’m going to separate the crude and do a chromatography test to see what I am dealing with because normally within a few hours you start to see some type of separation, Also The oils I’m winterizing has come from a third party in which I polish up products for folks and purge into shatter. Has any body out there experienced this before?


  6. Hi there,
    Why do you not recommend to use a Buechner funnel for removal of waxes?



    1. Hey,

      Surface area is king. The design is OK, but the size is not. The traditional porcelain funnels are much too small for any operation beyond the benchtop scale. Surface area increases with r^2 so small changes in radius can have significant effects. Also consider that once the waxes begin to accumulate on the filter, filtration rates suffer dramatically.


    2. Buchner is more than fine so long as you are not running large quantities.


      1. A buchner funnel setup off the shelf won’t be insulated so your filter will warm the solution being filtered. In my opinion, most bad winterizations are caused by letting the solution warm up before it passed the filter. It doesn’t matter for how long or how cold you winterized it if the lipids are allowed to redissolve. Added to this that they are slow, i.e. more time on the non-insulated filter.

        If you want to make more than a couple liters a day of distillate, you will need an army of Buchners or just a larger surface area.


  7. 2 question:
    1. Could I just put the winterized oil in a bottle, and let it sit over a filter overnight? Or will the fats absorb back into the solution if it warms up too much?

    2. I make RSO for my sister with rhumatoid arthritis. How I do it is I chop up some weed to rice-grain fineness, put it in a cooking oil filter bag, decarb it at between 110-120 degrees Celsius for 40 mins, then put it in the extractor, still in the bag. I’m using homebrew 97% ethanol (lab tested, no methanol present) with a soxhlet extractor set to heat up to between 90-95 degrees Celsius, (but I’ve seen it go up to 102 on the first few heat cycles. It’s just an electric hotplate controlled by an arduino) and I leave it running until the ethanol runs clear, after about a day or two depending on the weather. So far I haven’t had a batch that gets me high, but the extract shows 20% THC-A and 10% CBD on lab test results that some dude did for me. Typically use cheese. What am I doing wrong?


    1. 1. The fats will absolutely dissolve back into the ethanol. I cannot stress this enough, you must prevent the solution from warming as much as possible while you filter it. I have seen people do their filtration inside their freezer. You can also use a jacketed vessel. I also recommend covering with a lid in order to keep it cold, keep moisture out, and keep ethanol vapors out of your lab. If the solution warms past a certain point you have essentially wasted your day regardless of how small a micron filter you use.

      2. I don’t know much about edibles and I think I would need some more information.

      Extracting with ethanol, especially warm ethanol, should be short. I recommend looking into QWET (quick wash ethanol) extraction.


    2. You could try DECARBOXYLATION to solve the high issue. I have had very good luck with that process. Baking and such doesn’t normally allow for proper decarboxilation. Just remember to keep it covered as it cools, always use a glass dish for decarb and not longer than 20 minutes at 200degrees


  8. Dear Sirs I would love to learn from all of you, I recently bought a distillation equipment I am taking the first steps, I would like to produce THC and CBD for vape, could someone point me to a book about this work, which I can buy to have but knowledge, please ask the collaboration of all, any book that I can buy from now I’m very happy to be sharing this moment My name Ray


  9. I know im about a year late on this topic, i have had very good luck winterizing using 2 very common technics used in various forms of alcohol manufacturing that have both given my clarity and a higher proof during the distillation process. Over the past year we tried some of the most expensive products our their and we reverted back to true…time and tested ingredients and machines. My advice is search for past proven processes as we are working with an organic material just as in many different alcohol manufacturing.


  10. i like the page.its gorgeous


  11. During winterisation of a cannabis/ethanol mixture (1:5) does the lipids and waxes form in the top or bottom of the liquid? or are they floading around in clousters?


    1. I actually see all of the above. I don’t have a real explanation but three guesses are:

      1) Moisture content of the crude/ethanol solution
      2) Extraction solvent (supercritical CO2 will dissolve waxes that are insoluble in ethanol, thus more clumpy waxes)
      3) Winterization temperature (density of the solution)


  12. Can you use heptane to winterize? Or 95% EtOH and 5% heptane vs the 5% being water?


    1. In theory you can use a lot of solvents. I think the water helps precipitate out some of the lipids/gums. It really comes down to what the state regulations are.


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