Particles in roto boiling flask???


I have written several treatises on the pros and cons of 200 proof ethanol, 190 proof ethanol, denatured ethanol, and isopropanol (which is not ethanol at all).

Every one of those except 190 proof ethanol fails to perform highly selective extraction. They all extract vegetable oil (fats) and epicuticular wax to varying degrees, just like hydrocarbons do… and they keep a lot of those undesirable materials in solution even at very cold temperatures, just like hydrocarbons, but to a lesser degree.

Using 190 proof ethanol at -70°C is perfectly ideal. You still want to use short residence times (brief contact with plant matter) to avoid extracting sugars, proteins, and other deeper cellular materials, but 190p at -70°C is the most selective solvent for cannabis, period.

…and if you absolutely cannot stomach the taxes on potable (drinkably pure) 190 proof ethanol, you can use the new 5% n-heptane-denatured ethanol by adding 4.15% distilled water to it by weight. That will make the 95% ethanol present in the denatured solution into just over 190 proof instead of 200 proof. The small remainder of the needed water for the azeotrope will be absorbed from the air and plant matter (even dry plant matter has a little water available).

Speaking of which, re-proofing any 190 proof ethanol is only necessary if you intentionally add excess water to your resin solution, and then you force that excess water to mix with the azeotrope in your rotovap or other recovery receiving vessel upon recovery. To avoid doing that, perform recovery at 40°C or so until the ethanol azeotrope stops condensing. When you see white cloudiness in the resin, that is the excess water (that was not part of the azeotrope) emulsified with the resin. Drain your receiver of the azeotrope you recovered, then raise the boiler temperature to evaporate that water out of your resin. The water collected after the resin turns dark again (no more white clouds) can be tossed.


If I was going to be running counter current, kinda like a bizzy system or similar. Would that be a short enough residence time, along with efficiency of time and amount of solvent?

I appreciate the knowledge


See my edit above. I don’t know what you mean by countercurrent in an extraction process. Liquids or gases must be moving in opposite directions, such as in a condenser or other heat exchanger, for it to be called countercurrent.


Just curious what happens if i don’t add the distilled water to the 200 Proof Ethanol?
Is the 190 Proof required for the extraction process, or is a process issue?


I’m using the reference wrong, my bad. I’m thinking of a different phrase that I can’t remember, I’m sorry. But as using a chilled solvent tank and chilled column, like a standard butane extraction setup, but using ethanol. And from the collection to roto or treatment. Then spd.

I was under the impression that it was an efficient use of etho


If you open the bottle, you will end up with 190. Details on why 190 is better for this task are available from links provided in this thread.

Maybe check out one of the treaties @Photon_noir mentioned?

Ethanol Extraction White Paper


Is there any way to really modify a bho extractor to use etoh


@PofH As @cyclopath mentioned, 200 proof ethanol is hygroscopic (absorbs water from moisture in air) until it reaches the azeotrope of approximately 95% ethanol and 5% water. Yes, it is best to use 190 proof for extraction, Winterization, etc. Always cold and short contact times.

@dred_pirate No worries on misused terminology, I just wanted to clarify what you meant.

@PotHeadInASpaceSuit Sort of, but not really. Because one can use short contact times for almost any solvent extraction of cannabis, the whole “tube shaped extraction vessel” concept is rather outdated. If you look at industrial essential oil extraction facilities, you will find a lot of extractions being performed in a very short, wide vessel. This is because such a form factor minimizes the drainage time, thereby minimizing the difference in contact time between the top of the herb mass and the bottom. Also, as you are aware, ethanol takes more energy [e.g. than butane] to recover/distill out of the resin. That is why thin film technologies, such as rotovaps and FFEs are used in ethanol recovery. Granted, a very hot (and preferably stirred to avoid scorching) pot still also works for ethanol, but it is more complex and higher energy than a simple warm-water jacketed butane pot. Finally, chilling a column shaped extraction vessel and running cold ethanol through it is extremely lossy, since ethanol (and even butane) will only evaporate/drip dry from the biomass very slowly or not at all, even under vacuum, in super cold conditions.


It is easy, but like the wizard says above, it’s really not the most efficient way to go about it.

Very few mods necessary. I added a condensing coil in a freezer on my PX1.

I may even have used the dewaxer as my condenser on one occasion…

Temps are quite different if you’re not using a pump. You’ll need a pump to get shatter.

Because you’re adding more heat, your chiller might not be up for the new trick.


not sure how azeotropes would cause these, that would only affect the boilng point in the roto vap wouldn’t it?


By changing the polarity of the solvent system… b/c it becomes more selective towards undesirables.


Can you clarify? So the ethanol that is drained has water (azeotrope) in it and you drain that and then raise the temperature to evaporate the water out, so by this time the resin is ethanol free? Or we would be evaporating ethanol and water after raising the temp?


The azeotrope in question is ethanol:water mixture ~95:5, which all boils at the same temperature, together. Any excess water (more than the 5% in the azeotrope) will have the normal boiling point of water at your given pressure, which is higher than the b.p. of the azeotrope… so you have to raise the temperature and/or decrease the pressure to remove any excess water (from the resin) that happened to get into your azeotrope. If you do that without draining the distilled azeotrope, first, then that excess water will just end up back in your azeotrope.


Any distillation will yield you at best an azeotropic ethanol (190 proof). To get that water out of the azeotropic solution you need to use sieves. Since ethanol will vaporize at a lower temp than water, you can’t just boil off the remaining water. Raising the temp of the solution in the case of a rotovap will essentially be distilling the azeotropic ethanol out of your oil. After the ethanol is distilled off, you raise the temp to vaporize any remaining water from your oil.


Precisely! Yes!


So has anyone came up with an answer? After I cleaned up my “grinch” ethanol (celite 545 and aluminum oxide cryo filter, then room temp ac scrub in buchner funnel, while rotovaping last night, I’m getting the same Crystal’s in my BF. I’ve never seen this before in over 25 gallons ran.

I’ll try and get a pic a little later tonight


I’ve seen that before. It really could be a lot of things, though. Grit from the filter leaking? Sugar or protein from ethanol too warm during extraction? I have even seen what appeared to be very small THCa crystals forming.


Test water solubility. It is probably just more sugars/proteins/salts. Is this ethanol the same ethanol you ran the previous 25 gallons with recycled?


Yes, well 5 fresh unopened gallons, and 5 gallons used from prior wash/rotovaped. I have the bf on my table with a stopper. I’ll try what ever test I’m able to do it it with what I have. If I need to source chems I will gladly do so. But my experience is not with that type of investigation. Although I’m always willing to give it a try.

I tried sticking my dab tool and scrape some, but got very little. I did do a taste test, didn’t notice anything. Albeit a very small amount was tried.

I can try deionized water and see what happens, if it is sugars and such.


It’s easy. Wash it with a bunch of ethanol and see if it dissolves (I doubt it). Then wash with some water and I bet it comes off. Ergo not THCA.