What the Stink?!

I recently started running a little spd set up that has been treating me great. I’ve been learning a lot thanks to this site and other forums. I’m sure everyone already know that there’s a stinky ass musty smell when you distill.

I wanted to see if anyone with some science knowledge of some sort about what this stanky ass smell is. What’s causing this odor? Are these the terpenes getting burnt? Or is the boiling flask that hot that it just makes the oil smell bad?

Phospholipids being burnt off … this can be remedied perior to distilling and won’t stink up your work space . If not dealt with before touching glass , it might help to slow down temp ramping or stir reflux in order to ensure all volatiles have been boiled off

If you remove the terpenes prior to distillation you will find a significant reduction in foul odor. Removing chlorophyll prior to distillation along with waxes will also help with first pass odor but get rid of the terpenes first so they are not boiled along with the rest (terps begin to smell horrible at around 60C) of your compound and most of the foul odor you detect will be gone. Much odor is also caused if the boiling flask temp is set beyond 170C or so as this will generate smoke particulate however this might not be avoidable depending on your rig.

The smell is a myriad of degraded compounds. Degraded terpenes, phospholipids, cannabinoids blahblahblah. I guess you can say the terps are burnt but it would be more accurate to say the blasphemous amount of heat and time you exposure your molecules to said heat degrades these compounds into other compounds the stinky ones.

Follow the instructions of the prior posts, do whatever you can to get your vacuum below 100 microns. Then sell enough distillate to get a short path, your molecules will thank you later.

@Beaker you are suggesting a terp strip in the short path before distill any cannabinoids correct or another method of removing terpenes?

The terps can be removed with a liquid-liquid extraction. Keeping these alone out of the boil has produced far and away less foul odors plus recovery for me is much higher because I never need a pass to boil out the terpenes first.

Here is the link to the method. Next month I am running a lab that I predict will in similar fashion remove unwanted compounds prior to the boil but to dewax and remove chlorophyll(s) as well via LLE. I have no substantial photos or vids yet plus it will need fine tuning for sure but the point is really to keep as much out of the boiling flask as possible. I can already easily remove chlorophyll and waxes but my hunch is that an LLE wash can do it. Here is the link to the terp removal step:


Fair enough, to be accurate in describing your methods of removing terpenes you must disclose this is only removing the water/methanol (polar) terpenes not hydrocarbon terpenes such as limonene etc. You are aware this is misleading by only saying terpenes and not just water soluable (polar) terpenes?

prove it.


All terpenes are hydrocarbons by definition I believe. They will also all exhibit some level of solubility in polar solvents such a as water and methanol. They may not be highly soluble in polar solvents but there will be some dissolution!

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I can explain to you on the phone about how LLE and solubility work but I am sure you understand these concepts. My hypothesis is correct in terms of theory of these concepts. So it would actually be up to you to “prove” the current theory of these concepts wrong with analytical data.

Semantics: in science we do not prove anything we provide evidence that allow us to draw conclusions from observed, measured results.

Chemically you would not be able to explain why a polar solvent would solubilize non-polar terpenes let allow provide analytical data…

No, terpenes and flavonoids do not have to be hydrocarbons. There are many terpenes that have functionalization typically alcohols and other oxygen molecules in their structure making it more resonable for these molecules to be soluble in a polar solvent.

The majority of terpenes are made exclusively of hydrocarbons though.

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Found some limonene for sale, diluted in methanol.

(R)-(+)-Limonene solution

1 Product Result  

    CAS Number: 5989-27-5

certified reference material, 2000 μg/mL in methanol, ampule of 1 mL (Supelco)
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Multicomponent liquid−liquid equilibria measured at T = 298.15 K have been reported for the ternary (water + methanol + α-pinene or + β-pinene or + limonene) and (water or methanol + α-pinene + limonene) systems and the quaternary (water + methanol + α-pinene + limonene) systems. The mutual solubilities of terpenes (α-pinene, β-pinene, and limonene) in methanol and water have been measured at T = 298.15 K. The experimental multicomponent liquid−liquid equilibrium data have been satisfactorily represented by using the extended UNIQUAC and modified UNIQUAC models

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Terpenes are strictly hydrocarbons. Terpenoids are terpenes that have reacted and gained functional groups which alter their properties.

Fun fact cannabinods are terpenoids


If we’re gonna be nit-picky about terpenes vs terpenoids then I’m going to point out that for the most part the terpenes didn’t just “react” to gain those functional groups.

The functional groups were added enzymatically. Why is this relevant?

The stink the OP refers to is what you get when you randomly heat up a bunk of stuff and let it react. The joyous symphony that is the natural terpene/terpenoid/flavinoid from well grown elite genetics comes from deliberately selecting for the biological catalysts (enzymes) involved in the specific functionalization of particular terpenes (etc).

Edit: wish I had enough chemistry & physics to wrap my head around the papers @eliotoroboto linked. Any chance of an executive summary for the biologist?


What about linalool? It has an alcohol and is a terpene yea?

LLE works by relying on immiscibility between two liquids with the solvents having varying degrees of solubility constants on the solutes. If most terpenes are not as soluble in water methanol mix (which is what I am hypothesizing) then the molecules will stay in the “organic” (hexane layer). I would love to explain my doubt over the phone cuz these messages are a little lengthy to type.

Mod Edit: Removed the bologna.

It’s an alcoholic terpene created from the terpene limonene. Don’t think Linalool is classified as a terpene it’s a terpene derivative but I could be wrong.


Ahh i see! You seem to be more correct, however seems to be a bit more semantics but nevertheless you seem to be more on the right track my apologies. Thanks for Challenging me and being interactive.

Seeems as if terpenes are exclusively hydrocarbons made of isoprene units and terpenoids have some oxygen functionalizion (alcohol or ketone moiety)!


lets just pretend we’re trying to firm up the terminology so we’re all on the same page.

OR defined CO2 as a hydrocarbon, so there does need to be a little back and forth to get the terminology sorted.

“terpenes” as used in this industry often implicitly include the terpenols and terpenoids. so there is definitely room for confusion unless everyone is explicit.

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