Do not store these materials prediluted in EtOH (for months).

PeeWee678

Super Member
Jan 7, 2022
I know some of you rarely or never work with prediluted materials but if you do, please take note of the following.
I've experienced a few items deteriorating over time (over the course of 6 months or so) when diluted in ethanol (96%).

As you may know Ethanol partly converts to acetic acid, especially under certain circumstances. I'm not entirely sure but I suspect the ethanol reacted with those materials because in all cases I smell this acidic note and the undiluted materials were still fine (as well as hundreds of other diluted AC's and naturals).

Here are my materials I will not predilute in EtOH again (unless only for a few weeks or in small quantities).
If you experienced this with other materials as well, feel free to add them in this thread.
  • Vetiveryl acetate
  • Vetiver EO Haïti
  • Alpha Irone
  • Most of the Ionones (Alpha-, Beta- and Alpha-isomethyl ionone)
  • Patchouli
  • Gurjum Balsam
Luckily the list is short but I wouldn't be surprised if I'll have to edit this post soon.
Before you ask: I dilute my materials because it's cost effective and I'm just a hobbyist working with small amounts and a relatively small budget.
 
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Sam Macer

Super Member
Feb 26, 2020
I've had a similar experience with some raw materials, especially the ionones (and alpha irone). It makes me wonder; if it happens to predilutions, to what extent does it happen in final perfumes? I can imagine there's an argument for it happening less at representative dilution with some materials but I would be interested to know if perfumes with ionones have a shorter shelf life.
 

PeeWee678

Super Member
Jan 7, 2022
but I would be interested to know if perfumes with ionones have a shorter shelf life.
My thoughts exactly. And indeed it could depend on the concentration but then again, I'm pretty sure there are perfumes out there with overdosed ionones, vetiver, etc. that, in theory, could deteriorate in the same manner. Complexity and good top notes would of course be able to mask those off notes. Maybe that's the secret? Or would BHT help to slow down this process? I add BHT to many EO's but not to vetiver or ionones...

So if someone with lots of experience wants to chime in on this, feel free ;)
 

papadooku

Basenotes Member
Nov 2, 2022
I've had this happen with patchouli EO ! It ages wonderfully when pure, but it became more "cold" and way less rich over 6-12 months. So for us pre-diluters, better to make very small batches so they run out faster.
 

PeeWee678

Super Member
Jan 7, 2022
I just discovered it also happened to my Patchouli, Gurjum balsam and most of my ionones.
I edited the list in my first post above.
 

emrego

Super Member
Aug 4, 2016
+1 for a-irone, a-ionone, patchouli and vetiver haiti...the same acidic, slightly rancid effect is also significant when used in blends. If you've ever smelled a vintage perfume that went bad, this is exactly it. Good topic, thanks for bringing this up folks!
 
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sorance

Super Member
Feb 14, 2020
With this logic, all fragrances should go rancid if you used patchouli or vetiver in formula. But if you are talking about the aging, the ethanol will stop it.
 

PeeWee678

Super Member
Jan 7, 2022
With this logic, all fragrances should go rancid if you used patchouli or vetiver in formula. But if you are talking about the aging, the ethanol will stop it.
I completely agree and no, I'm not talking about the aging; it's really about the forming of (what I assume is) acetic acid and I have no idea why this doesn't happen in (commercial) fragrances but it could be the addition of BHT in those.

I excluded the possibility of headspace in the bottle; yesterday I had the same problem in a full bottle of Gurjun balsam.
Also my bottles are well sealed and the undiluted materials are all still fine so it must be a reaction with the ethanol.

I have some tests prepared now in which I will compare storage in EtOH 96% without BHT and with BHT.
Testing Vetiver Haiti, Alpha ionone, Beta ionone and Gurjun balsam.

I will post the results as soon as I have enough significant data.
 

Capybaron

Basenotes Member
Jan 28, 2023
Just chiming in that so far my dilutions of Patchouli, Vetiver or Gurjun balsam haven´t turned rancid, also having stored them at least for half a year so far.

I´m not using any BHT in those, so far, either.
I´m also wondering, if your experiences are not due to any other factors, how professional perfumers avoid this issue. Given how commonly used the ionones and patchouli are, i´d expect that there would be a wealth of information available on this topic, but i haven´t seen seen it mentioned once that something might turn rancid/bad in alcohol.

Just a random thought- I have not looked into the conditions under which alcohol turns to acetic acid, but maybe whether and how the alcohol is denatured might influence it.
 

PeeWee678

Super Member
Jan 7, 2022
Just a random thought- I have not looked into the conditions under which alcohol turns to acetic acid, but maybe whether and how the alcohol is denatured might influence it.
Not a random thought at all ;)
I haven't mentioned it but that's why I also had prepared a sample with a "different kind of Ethanol" (both denatured but differently, 96% and 99.8%).
 

RomanB

Basenotes Junkie
Oct 22, 2022
With this logic, all fragrances should go rancid if you used patchouli or vetiver in formula. But if you are talking about the aging, the ethanol will stop it.
Patchouli is a paragon of rancidity for me. I tried numerous variants of it and perceive mold notes in every one. Maybe that’s personal and I have some receptors that react so.
 
Aug 19, 2021
I'm also very curious to know how this affects the final perfume composition. I had some patchouli at 20% develop a lot of acetic acid, smelled like nail varnish, Benzyl Acetate like. So yeah what's to stop your final perfume composition from developing acetic acid over time?
 

jsweet

Super Member
Sep 16, 2021
Patchouli is a paragon of rancidity for me. I tried numerous variants of it and perceive mold notes in every one. Maybe that’s personal and I have some receptors that react so.
If you perceive the mold only in patchouli oil and not Clearwood, it's probably the pogostone giving that effect.
 

Dan 3.141

Super Member
Dec 13, 2021
I use pre-diluted materials for RnD and haven't had as many issues as reported here. I have noticed that after 6-8mo. Beta Ionone, Alpha Irone, and some of the aldehydes (Aldemone and 2,4 ivy carbaldehyde for example) will degrade, but this happens whether diluted or not. I use pure organic 200 proof ethanol and store certain materials in the fridge once diluted. I have never had issues with Patchouli or the others you mentioned. Maybe try the anhydrous alcohol instead.
 

PeeWee678

Super Member
Jan 7, 2022
I use pre-diluted materials for RnD and haven't had as many issues as reported here. I have noticed that after 6-8mo. Beta Ionone, Alpha Irone, and some of the aldehydes (Aldemone and 2,4 ivy carbaldehyde for example) will degrade, but this happens whether diluted or not. I use pure organic 200 proof ethanol and store certain materials in the fridge once diluted. I have never had issues with Patchouli or the others you mentioned. Maybe try the anhydrous alcohol instead.
I've been thinking about anhydrous alcohol but here in Europe that's over 10 times the price of denatured alcohol (about € 100,- for one litre).
Even then that's not 100% but only 99.5% so I guess it contains some water.

I have to say though that of my 300+ dilutions, only the ionones, patchouli, vetiver and gurjun balsam seem to have developed this acetic note (so far). They're small 3ml and 5ml bottles so no real loss, it's more of a nuisance and important to pre-smell from now on. ;)

Hopefully the BHT I added to my test bottles will do the work; I already started adding BHT to new predilutions just in case.
 

truthadair

Basenotes Member
Dec 16, 2021
Interesting, I haven't had this problem, and I use pure undenatured alcohol. I usually replace dilutions after about 6 months though anyway. Could the denaturants they use in perfumer's alcohol be a culprit?
 

Dan 3.141

Super Member
Dec 13, 2021
I will add this for what it is worth; I have noticed that A.C.A. does not keep well diluted and refrigerated. It's better to store small amounts of diluted A.C.A. in a cool dark place. However, I find it better to store H.C.A. in the refrigerator after diluting. It degrades faster when it is not stored at refrigerated temperatures after diluting. Love these materials but not the most stable. If you are diluting these materials, make small amounts and don't plan on storing them long-term. Use em or lose em
 

Culpa Ire

Basenotes Member
Nov 11, 2022
Yup. My HCA was just over a month old after receipt before it turned into a combination of cat's piss and wet cardboard.

Perhaps I missed a trick by not using it to create a new divisive note in a composition.
 

editorinscent

Basenotes Dependent
Oct 3, 2007
Are you sure it isn't from the container you're storing it in? I use a lot of glass vials from Amazon with plastic (non polycone) caps for quick and routine work, and I have determine it is the paper/polymer coated lining in the cap that has contaminated so many of my dilutions.
 

Dan 3.141

Super Member
Dec 13, 2021
Yup. My HCA was just over a month old after receipt before it turned into a combination of cat's piss and wet cardboard.

Perhaps I missed a trick by not using it to create a new divisive note in a composition.
It should not have gone bad that quickly; store at lower temps and perhaps research supplier. I find the quality can vary and sometimes greatly depending on the sourcing.
 

Dan 3.141

Super Member
Dec 13, 2021
Are you sure it isn't from the container you're storing it in? I use a lot of glass vials from Amazon with plastic (non polycone) caps for quick and routine work, and I have determine it is the paper/polymer coated lining in the cap that has contaminated so many of my dilutions.
polycone caps are the way to go
 

Culpa Ire

Basenotes Member
Nov 11, 2022
Are you sure it isn't from the container you're storing it in? I use a lot of glass vials from Amazon with plastic (non polycone) caps for quick and routine work, and I have determine it is the paper/polymer coated lining in the cap that has contaminated so many of my dilutions.

It should not have gone bad that quickly; store at lower temps and perhaps research supplier. I find the quality can vary and sometimes greatly depending on the sourcing.
It was supplied by a widely respected seller in an internally coated aluminium bottle and stored in a fridge upon receipt. But I’m pretty on the ball when it comes to materials anyway - my lab is air-conditioned so it remains at a constant temperature throughout the year, so storage problems aren't an issue for me.

My theory is it was close to unusable state when it was received, or maybe I received it when it was warm out or it spent a weekend at the carrier's warehouse or a combination of calamitous events, who knows. I only had cause to pull it out because I’d set my mind to making a jasmine accord that summer. Turned out I didn’t need it for that anyway, so no great loss and it was only 30ml. Never had call for it since.
 
May 18, 2020
Maybe someone more versed in chemistry can confirm, but aldehydes readily form acetals with alcohol, and ketones (including ionones) can also from acetals, right? All of the materials listed in this thread either contain aldehydes, are aldehydes, or are ketones (ionones).

Acetal formation could be what we're all smelling in our pre-diluted samples?
 

RomanB

Basenotes Junkie
Oct 22, 2022
Maybe someone more versed in chemistry can confirm, but aldehydes readily form acetals with alcohol, and ketones (including ionones) can also from acetals, right? All of the materials listed in this thread either contain aldehydes, are aldehydes, or are ketones (ionones).

Acetal formation could be what we're all smelling in our pre-diluted samples?
When acetals are formed, water is released. Water causes acetals to decompose back. So they are always in equilibrium, and since regular alcohol always contains some water or takes it from the atmosphere, acetals in perfumer’s alcohol solutions form slowly and not completely.

Many aldehydes are deliberately stored in alcohols to stabilize them.
 

parker25mv

Basenotes Dependent
Oct 12, 2016
I do not know, but my intuition tells me if there is a problem you might want to try using 100% ethanol (that does not contain any water).
Unfortunately it can be harder to find.

If you want to go into the complexities of the chemistry, the simplest molecule with this type of group is acrolein. A MDSS says "Reacts slowly and exothermically with water to give 3-hydroxypropionaldehyde."
I would guess that bigger molecules such as ionone would behave similarly, except that they are much less reactive and react far more slowly. (if even one of the hydrogen atoms is replaced by a carbon group, it drastically changes the reactivity... off topic but one can take a look at the large difference in allergen sensitivity between ordinary cinnamic acid and alpha methyl cinnamic acid, which I suspect is caused by this effect, or of course the huge difference in reactivity between aldehydes and ketones)
These sort of reactions can be very slow, not even obviously noticeable, but could result in enough impurity to change the smell.

Now you might ask, well how do these molecules exist inside plants, since plants contain so much water? Well, these molecules are probably specifically stored in tiny oil sack membranes inside the plant cells, where water does not exist.

Of course the presence of an acid (or alkalinity also) is only going to greatly accelerate the reaction rate with water.
 

acidnbass

Basenotes Member
Jun 29, 2015
This is a super relevant topic for me since I have also run into a common and strange effect in some of my EtOH-diluted materials (and some of my favorites at that!), and there are quite a few I'd add to the list:

- farnesol
- farnesene
- santolol
- firstantol
- Caryophyllene oxide
- beta-caryophyllene
- Cedroxyde
- Piconia
- Dihydro Ionone Beta
- Boronal
- Guaiene


I'd say, of this list, the biggest offenders are farnesol, boronal, santolol, Cedroxyde, firstanol, and guaiene. Boronal is another level of sour/gross, and I think there is more going on there, but they all share a similar sour, plasticky type of aroma. Also, this aroma tends to be a top note and is relatively fleeting—santolol and firstantol, for example, when put on a scent strip, will reek of just this off-note, but then it will go away and eventually the dry down is the normal characteristic aroma of the material. For this reason, I don't think the source-molecule itself is changing, but that it's somehow causing the ethanol to form an off-note, like an acetate. I'd be super interested to hear from someone with more chem experience what that might be. For most of them, then only similarity is having an alcohol, carbonyl, or epoxide group (save for guaiene and farnesene), and almost all of them (except for farnesol and bornal) have a woody-type aroma.

I haven't tried adding a preservative to these materials when pre-diluted, or pre-diluting in another solvent like TEC to see what would happen. However, it makes me wonder if these materials will cause the same off-note top-note when in mixtures in finalized perfumes, and if so, how to prevent that.
 

PeeWee678

Super Member
Jan 7, 2022
I haven't tried adding a preservative to these materials when pre-diluted
About two months ago I made a test kit (several materials with and without BHT) but I think it will be noticeable after about 4-6 months so at this moment I still can't say if adding BHT will help.

It is indeed certainly a (medium long) top note. There is a good chance it's not even perceptible in a perfume when masked by potent top notes like Bergamot (also depending on the amount used of course) but I did replace the faulty predilutions with fresh ones (and smaller amounts until I have found a solution).
 

acidnbass

Basenotes Member
Jun 29, 2015
About two months ago I made a test kit (several materials with and without BHT) but I think it will be noticeable after about 4-6 months so at this moment I still can't say if adding BHT will help.

It is indeed certainly a (medium long) top note. There is a good chance it's not even perceptible in a perfume when masked by potent top notes like Bergamot (also depending on the amount used of course) but I did replace the faulty predilutions with fresh ones (and smaller amounts until I have found a solution).

I’ve been able to formulate with these off-materials in compositions with top notes and it can definitely be masked (even in some cases add mor body to the top), but it changes the character a bit. When mixed with other materials, It seems only really noticeable in the first minute or so, then tends to simmer down. Definitely requires a fresh dilution to get a cleaner evaluation, especially for things like the top notes and subtle mid-basenotes like farnesol.
 

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