Winterization - how much increase in potency is reasonable to expect? And other Q's

Doing ethanol extraction at ambient temps from ~4% CBD content hemp. We are moving towards doing extraction at -40 so as to not have to winterize in the future but this is what this batch and associated data was extracted with. Also moving towards some better % cannabinoid biomass too but this is what we had to work with while setting up and refining our extraction process.

A pre-winterization sample of the crude generated by the ambient temp extraction was sent to the lab - and I know it still had some residual solvent to make the crude flow a bit easier for when we would pour it to winterize. Lab results said 45.9% total cannabinoids on the unwinterized crude.

After chilling a 10:1 Etoh:crude mix down to -45C and filterizing we sent a sample of the winterized oil off to a local lab (Botanacor in Denver) which came back at 49.1% total cannabinoids.

I now have a bunch of questions regarding winterization and lab testing

  1. My CBDa content reduced between the crude and winterized samples from 3.32% to .51%, and CBD content went from 39.98% to 45.84%. No THCa in either one. This suggests decarboxylation of the CBDa due to heat to me - is this assumption correct? We run our rotovaps at 85-90*C bath temperature.

  2. In the same span of lab tests, THC content went from 1.55% on the unwinterized crude to 1.63% in the winterized oil. With no change in THCa that change had to come from somewhere - I wonder if this is explainable by tolerances on the testing equipment or lack of total homogenization of the crude. I think I need to call the lab Monday and ask some questions about what kind of % tolerances their equipment has.

  3. What would one expect to see as far as potency difference between crude and winterized steps for a “successful” winterization? I expected more than a 3.2% increase in potency for the amount of fats that were removed during our winterization process. At the same time I’m assuming that there is some nonzero amount of cannabinoids that get lost with the fats which are removed during the filtration process, but for the amount of fats and waxes that were removed I definitely expected a higher increase in cannabinoid potency

  4. At what increased cannabinoids % point does winterization become “economical”? I’ve heard of a local guy charging around $300/kg for contracted winterization services (no clue if thats for crude on the incoming side or winterized oil on the outgoing side). I know people are willing to pay more money for every additional step further refined towards isolate the extracted crude becomes, but damn, that seems really expensive considering the relative cost of the equipment necessary to winterize.

  1. Is there any SOP on reprocessing the removed fats or dirty coffee filters that were changed out during the filtering process? Just trying to minimize any and all cannabinoids that might be otherwise left behind.

  2. Any papers or explanation of what the % non-cannabinoid content is comprised of once all the lipids and waxes have been removed by a successful winterization?

  3. Just a random question I had and not part of my procedure, why can’t you use heptane denatured ethanol to winterize?

Obviously if you’re fully vertically integrated going from extraction all the way to isolate in house you don’t have a choice, but my capitalist tendencies say to do the least amount of additional steps you can for the maximum financial gain, and focus on what you do best.

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Most likely. That’s pretty hot, whats your vacuum level? I run mine around 40-60c.

Most labs I’ve worked with are +/- at least 1%

You can always get the fats tested to determine potency for residual Cannabinoids. I’m suspecting that when you do all your weight and balance accounting you will find the lab to be the issue, not your procedures.

Not sure what you mean with number 4.

You can dissolve the fats in ethanol and winterize again, the high etoh:Cannabinoid ratio should force most of the Cannabinoids to stay in the ethanol.

That would be nice…

Some of the fats are soluble in Heptane and won’t freeze precipitate.


I would say the analytic lab is not great. I have met a lot of “qualified” chemists who are not the smartest humans nor do they have the best understanding of chemistry which is sad :frowning:

If you want something done right you have to do it yourself…95% of the time. So I would suggest looking into doing some in house analytics because then you will atleast know for sure that your testing is consistent. If you are still seeing strange results you can be sure that there is indeed some chemical changes occurring during the winterisation and not just getting bad results from a lab that is probably run by ppl who don’t give a fuck about the accuracy of their testing because the outcome doesn’t effect them.

Not all chemists and labs are duds though but don’t trust them blindly either

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Varies (been making a bunch of changes to equipment and layout lately) but for the most part we aim for .06-.07 mpa. We are still refining our process, is there a problem with running the rotovap baths that hot, either during primary solvent evaporation and recovery or when the oil goes thru a second time for winterization solvent recovery?

I’m thinking I want to get the fats mixed together really well and then tested for cannabinoid content because I’m curious if this is a worthwhile endeavor. Not eager to plug up a bunch more large coffee filters if its not going to net us very much additional CBD.

Minimizing the time the extract is hot is always ideal. But hold on, are you extracting with ethanol, recovering all of the ethanol, then dissolving in ethanol again for winterization?

After extracting with ethanol, recovered (estimated) 95% of the ethanol so the unwinterized crude would flow a little better, remove from rotovaps (and clean rotovap glassware), dissolve 10:1 in ethanol in a jacketed reactor at room temp, chill to -45C and filter using a benchtop buchner, then back to rotos for final ethanol evaporation (this time removing all ethanol).

I’d love to only remove a certain amount of ethanol so I wouldn’t have to redissolve but I don’t know how to measure that ethanol content %, especially when the fluid is spinning in a rotovap globe…

In the future I don’t want to winterize at all if I can help it which is why we’re moving away from ambient temp extraction and towards extractions at -40C

For the initial recovery of ethanol from the extract solution using a still could be much easier than a roto vap

If your extract yield is consistent you could figure out the amount of ethanol you want left in it to winterise. You could then figure out when you have reached that point of recovery by weight or volume of the still