Remove Harsh aftertaste

My starting material is winterized CO2, after the second run distilling, the oil comes out almost water clear. The only problem with the oil is that it has a strange aftertaste (like rubber, it also tickles the nose)

I thought it was sulfur but the oil passes the copper test.
Then I thought the starting material was sprayed with Neem oil, but the lab results show no traces of azadirachtin.

When I put a sample of the oil in distilled water, the water turned into a light rose color.

When I dissolve some of the distillate into ethanol so I can give it a carbon scrub, the ethonal turns a light orange. After filtration and rotovap, the oil becomes mucky, and still has some of the aftertaste still present.

I am at my wit’s end trying to figure out what is causing the bad aftertaste, as adding terpenes does not get rid of it either.

Any ideas what can be done?

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I would try saline washes if you haven’t already. I find that my scrubbed distillate doesn’t have a smell and Id imagine that could help the taste.

Sorry for my ignorance, but I have never done a saline wash. Do you mean just add saline (water+salt) to the distillate and then remove the saline from the oil? Or should I implement a hexane saline wash?

If you type “saline wash” in the search bar you will find sufficient information on how to do it.

To sum it up, do first pass, take your distillate and dissolve 1:1 up to 1:4 (distillate:hexane/heptane) and then rinse that solution 1:1 with super-saturated salt solution. Discard saline water and repeat the rinse. Keep rinsing until water becomes clear and then do one more for good measure (I used mason jars to shake for rinsing on small batches). Then just roto to recover your hexane/heptane. After this, you can do your second pass. Hopefully it gets rid of that smell!

Read up more on it though because my explanation is extremely limited.


Likely smoke particles entrained in the distilate during thermal degredation. Typically this would occur at temps above about 170C oil temp irregardless of vacuum and depend on most likely what kind of fats are still present.

Every oil has a smoke point past which the fats begin to break down into acrid stuff. I routinely open my sublimator for harvest to find smoke lingering inside. Smells like burnt transmission fluid kind of. I believe it is because of fats still present at least in part.

Heated past its smoke point, that fat starts to break down, releasing free radicals and a substance called acrolein, the chemical that gives burnt foods their acrid flavor and aroma. You posted something water soluable more or less as contaminate. Since this is just a guess I would look towards remediating the smoke particles. You can rid most of that stuff on a small scale with pyrolysis. Even a pass through some alumina in a buchner funnel in solution with rubbing alcohol will likely do it.

Pure speculation but let me suggest you use the common sense of taste. Touch the tip of your tongue to the compound. Does it taste burnt?


Thanks for the advice, I will try this with a small sample batch. Should I dissolve the sample in ethanol and run it through a cake bed of alumina? (I was thinking a 1:2 distillate,ethanol ratio)

I tasted a sample of the oil, and it does not taste burnt, just plain oil. (My taste buds might be fucked)

I personally only use rubbing alcohol with water for something like this but I see no reason ethanol and water wont work too. That nasty smell is hard to get out. If you prewet the alumina a bit with water it should help I am guessing too. I would run any ratio that gets it disolved. You may see an aqeous fraction elute before the cannabinoids if you run it with a mix of 70/30 water to ethanol. I do with iso.

I hope this helps.

Thank you for the advice, but I am afraid it did not turn out as I was hoping for.

After running the clear sample batch through a bed of alumina, and rotovap, the oil turned out murkey. (but has a semisweet smell to it)

I left it on the hotplate and let it stir for about an hour, got rid of most of the water that was left over, but I am not sure if it’s going to turn clear.

Curious if this was tried on a sample, and results.
Related thread Pyrolysis Video

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Did I understand right that the foul odor is gone but with the side effect of an opaque but sweet oil now?

It would pop and sputter considerably. I have ended up with pretty burnt oil and nearly always burn it out of the extract using my trusty ceramic dish. It snaps and pops as that stuff turns to carbon and dust in the burning of it. Still though a milky white mixed with the compound after a pull through alumina is a bit odd don’t you think? I mean if the alumina was fresh and inert the only thing that happens are some things are removed and not added. The exception is abrasive grade grit can have very fine dust with it that can end up past a course frit. I have pulled it through with water first which is how I prep an alumina column and seen a milky taint to the water because of superfine alumina (called “fines”).

That would be the only case when something got added but that seems remote. So what got removed then to make it opaque?

edit: that looks like oil not purged under vacuum and would be an explanation of what got added. It might not be the right explanation but a sweet smell indicates alcohol and opaque indicates possibly a whole lot of microscopic bubbles with the azeotrope of ethanol and water trapped in oil. It is impossible nearly to boil out without deep vacuum as it is almost an emulsion. Theory only but it fits.

Here is a test to see if you still have water and solvent in your compound.

Put a pea size dab on a butter knife and hold it over glass for recovery. Light a Bic lighter under the knife so that the heat makes it run off the knife but through the flame you are holding at an angle.

If there is solvent in the compound it will pop and sputter considerably. If there is solvent in it from the alumina filtration still it should be obvious. The bonus of this test is the drippings are now mostly clear of the solvent so it will vape great but be a bit black from carbon (Bic).

The odor of the oil was never really the big issue it was the aftertaste that was causing an unpleasant flavor.
When I add terps to the oil, it masks the smell of the oil, but does not get rid of the aftertaste.

I’ll try your advice, and let you know how it went with the pea size dab.

So the pea size dab, did pop when it went near the flame, but I am not sure if that means there is still water in the solvent or there is alumina still present. I will put the sample batch into a vacuum chamber to see if any traces of water can be sucked out.

Thanks for the vacuum idea, I put the warmed up sample inside the vacuum chamber and just let it sit for an hour, it is starting to turn clear. (just has a dark color to it, I guess from oxidation?)

So after vacuuming it, and heating it up, the oil turned out clear, and orange. (the right one)
The cartridge on the left is the starting oil.

But I am afraid both carts still has that strange aftertaste. When I blow smoke through my nose, it makes my nose seem like it wants to sneeze.

You need to apply agitation inside vacuum … what I find to work best to remediate that smell/taste is to take the collection flask and drop it on a hot plate . Attach either a glass adapter or monocow to flask in order to line it to a cold trap → vacuum … I’ll bring it from 120-150(160max) in about an hour or so and by the time it’s hit max temp the trap will have the same exact light pinkish viscous liquid you showed in water … cant figure it out either tbh and test comeback inconclusive (they don’t test for whatever it is lol) stirring/heat/vacuum is key to this just as it is to SPD … works FR me every time ! Good luck !!


Do you turn off heat and keep vac on until boiling flask is under 100c to avoid the smell/taste?

I will keep heat on until I see that all the pockets of whatever is boiling off stops … it’s almost sweet to the smell once collected and aerated :man_shrugging:t2: