Wednesday, July 16, 2008

An Iris Problem: How to Build One

I got a most interesting mail the other day: Someone who is clearly very much a perfume lover and whom I knew before through the blog was asking me what I thought was a perfumer's perfect way to build a masterful iris. It surprised me because I am not a perfumer myself, but intrigued my nerdy tendencies enough to devote a post to it.
I have to put a disclaimer here that the post will feature some chemistry and might be perhaps a little boring for those of you who'd rather read ethereally poetic reviews about fragrances or some comedic spoof take on popular trends. But despite all that and knowing it won't be too popular, I thought it was worth addressing and I promise I will try to state it as simply as possible and even include a small index at the bottom for your ease.

Our reader has been reading what many of you have too: The Emperor of Scent by Chandler Burr, Luca Turin's Secret of Scent and Perfumes, the Guide, many online perfume blogs and boards...the works! Based on that and some knowledge of chemistry on the reader's part, those are the questions posed:

"I know α-n-methyl ionone (aka Givaudan's Raldeine A) was the chief component featured in Iris Gris. I also remember that one also needs irones; they are crucial, since it's this group of compounds that give orris its distinctive aroma.
Now, problem number one: which irone isomer(s) {1} should one use? I know orris emits at least three irones: cis-gamma, cis-alpha, trans-alpha irones. Octavian mentioned alpha irone in his Iris Gris entry (didn't mention which enantiomer {2} was used in Iris Gris). So what would be your pick? Is there a commercial blend, say, from IFF, that produces a good irone bouquet?
Then there are the interesting molecules....I remember Chandler Burr mentioning something about methyl ionones, which is a bit confusing since I assume ionones must have a methyl group stuck with them as well. Is this necessary? In addition, Dr. Luca Turin also talked about Maurice Roucel's ingenious use of Irival (produced by IFF), a nitrile{3} that gives Iris Silver Mist it's interesting quality. Now I'm lost..."

The question is interesting because it goes to the heart of the matter: in order to build a solid, good, true iris, where should the perfumer look?

To my understanding, irones are higher analogues of ionones, because they contain an additional methyl group in the cyclohexane group.
Although irones are indeed present in natural orris, it seems that production of a-irone has become standard, starting from a-pinene via the Caroll re-arrangement. [Basically the schema is going like this for anyone taking notes: A-pinene goes through decarbonylation, gives methyl trimethulcyclobutyl ketone, they add acetylene, there goes the Caroll re-arrangement, we get (trimethylcyclobutyl) heptadienone, pyrolysis is induced, giving methylated ψ-ionone and through cyclization this gives α-irone.]
Let me at this point clarify regarding the Greek letters (α: alpha, β: beta, γ: gamma) in the nomenclature of irones (as well as ionones and damascones) that they refer to the position of the double bond after the ring closure, while n- and iso- to the position of the alkyl group (assuming something other than acetone is used in condesation).

I suspect this ease of production is the reason why we have been flooded with iris fragrances the last couple of years: like Octavian pointed out, it has become easy to synthesize, not to mention it is a great marketability tool in a milieu which thrives on semi-info (the perfume lover usually knows that iris is the most expensive natural ingredient). Two birds in one shot!

But wait: what was that interesting molecule that Chandler Burr was referenced to mention? It must be a-iso-methylionone which had been erroneously mentioned as γ-irone in some old texts. At least, I suppose so... Therefore another irone, used to produce an iris effect.

Concerning Iris Silver Mist and Irival, let me set this straight. The info is not that Irival gives the fragrance its very specific iris scent (I just checked Luca's book before I typed this), but that it has been used in conjunction with other things to produce the ethereal, sad and grey rooty effect that we smell in Iris Silver Mist. Maurice Roucel, the perfumer behind it, used every ingredient he had acess to that had an iris descriptor attached to it, prompted by Lutens who urged him to produce an iris to the max.
There are possibly myriads of ingredients that have an iris descriptor attached to them (meaning they have some nuance of iris in their odour profile); if one reads lists of ingredients one sees that. To reference an example: Like we say that oudh has a musty woody but also nutty nuance when we smell it, the same applies for other ingredients, some complex like natural essences and some less so like single molecules. Roucel probably used all the ones available to him at the time and in the company he was working with.

Basically what I have concluded is that there is no single molecule that alone could account for a sublime effect on any perfume, be it an iris one, a certain jasmine effect or the surreal ones such as those based on dusty lamp and linen drying in the wind notes. Although we're often made to think that chemists discover magical aromachemicals/single molecules (and they do) which in bullet-form could almost fuel a rocket, to bring an analogy, I think that it has to do with context as well. The interaction of different ingredients with each other accounts for many pleasurable and not so pleasurable sensations and therein lies the artistry of perfumery. Rose and patchouly for instance do wonderful things to one another, which is probably why they are often combined. But with what different effects: smell Voleur de Roses side by side with Aromatics Elixir. The result is dissimilar. They are both based on this accord, but they go in different directions from there. Otherwise every chemist would be a perfumer! It takes however something more than that to become the latter.

The secret of producing a masterpiece iris -or anything else for that matter- lies in the artistry of the formula and the sleight of hand of its creator.

{1}.Isomers are compounds with the same molecular formula but different structural formulae.
{2}.Enantiomers, like their Greek etymology alludes to, are stereoisomers which have a mirror image of each other, much like one's own hands (the same, but somehow opposite).
nitrile is any organic compound which has a -CN functional group (that is a carbon and a trible bonded nitrogen).

Pic of perfumer Alberto Morillas courtesy of Basenotes.net


  1. This post is so interesting! Just a curious question, are you working with chemistry?

  2. Thank you, L.
    I am not in a position to divulge; mailing you ;-)

  3. Helg , I read it but I am now very confused and need a lie down. LOL

    *Maths and chemistry were not my subjects

  4. Oh, sorry about that, M!
    I found it an interesting question, although I anticipated it wouldn't be very popular, LOL

  5. Anonymous08:20

    Helg, this is fascinating! I am really excited now about YOUR first perfume!! Iris will surely make a good part of it... :-)

  6. In an orris fragrance there could be ingredients to build the distinctive orris note and others to give the special direction of the perfume. You can have a floral-orris, a woody-orris, a powdery-orris, orris like the natural concrete, and even a gourmand-orris (the natural is used in flavours too!!)... etc
    For the distinctive orris note one might choose:
    the methyl ionones (gamma), ionones (alpha floral violet and beta woody) and irones (alpha the orris most used).
    for a distinctive concrete note some accents provided by nonenal trans 2, nonadienol and nonadienal (green cucumber both).
    some green violet note (liffarome, methyloctinecarbonate, etc)
    but also Iritone, Orrivone, Orriniff or Azarbre and Rhuboflor (not orris notes but can go well with)
    some naturals - orris products, cassie flower abs, violet leaf abs, mimosa abs.
    unusual notes like aldehyde C12L, some fatty alcohols and their esters, cumin oil, costus ollifac.
    carrot seed oil has a distinct orris suggestion and if a special quality from Lab.Monique Remy is used you'll get also the apricot-peach velvety note (your orris could get an osmanthus note)
    for the drydown orris goes well with woody notes from cedar and vetiver family. There is a wide option here (IsoESuper, Vertofix, Vetiver haiti oil, vetiveril acetate, etc) or Boisiris,
    for the powdery notes, again a wide option from heliotropine and vanilla absolute to balsamic notes
    In the end some musks, powdery and animalic (muscenone, musk ketone, muscone).
    even ambery notes (ambroxan) like in DiorHomme.
    What is an ideal orris? It could be so many things and it's the artist's option to provide an original twist.

  7. Oh, N! I wouldn't dare to think that! I do love iris though :-)

  8. Dear O,

    thank you for stopping by and devoting time in providing fascinating info as always.

    I admit that carrot seed oil does have a turnip smell about it to me and orris has that too sometimes (Iris Silver Mist is a case in point, especially in certain weather conditions which bring out the earthy more). So am I to deduce LMR carrot seed + orris= osmanthus? That's interesting!
    BTW, I was having a conversation on Iso E Super the other day, it was referenced as musky, but to me it's not.

    I do get lots of heliotropin in the lightly powdery Infusion d'Iris, although nobody mentions it. Now I know I am not delusional :-)

  9. It is very interesting reading this chemistry post. The symbiosis between the different constituents must take many years to appreciate and many mistakes made before a classic scent is perfected.

    With the natural orris products the growing conditions must play a large part in the eventual quality of the fragrant constituents.

  10. It is not complicate to simulate a certain odour (in this case the orris) but the hard work begins only after.
    There is not a standard natural orris smell and the beauty is that all types of orris extraction products have a different facet. There was also a "black orris" extract. Not because it was magic but because the roots were not peeled. :)
    A beautiful product was (it's not used anymore) the orris tincture - very soft, delicate and almost edible.

  11. I have some orris growing in my garden. Although I am loathe to harvest roots I am very tempted to see how orris root tincture would turn out. I wonder if it has any medicinal potential, I shall have to do some research.

  12. amanda: curious to see the results of your experiment. I did it years ago (the same with oak and tree moss.

  13. Amanda,

    I know of at least one perfumer who tinctures her own materials. Of course we're talking small scale production, but the results are so worth it. You can read lots of info on that on the Net and it pays to do it properly.

  14. Dear O,

    Black orris sounds so "du jour", doesn't it? LOL :-)
    I have heard and read about orris being used in food and in fact I know from history that ancient Greeks were not adverse to eating (powdered) and making a herbal tisane out of it.

  15. I was thinking the other day that florals tend either to be sensuous or delicate, and iris demonstrates both to the extreme. Perhaps one cannot have a perfect iris scent, for that reason, unless one could somehow suspend these contrary elements in time.

  16. I am not so sure, because some are downright brutal (yet beautiful) like tuberose, or waxy, solid and detached like tulips.
    I can't but agree with your latter statement though. And perfection is really a subjective term in such matters anyway.

  17. I have just read one of my texts and it says orris needs to be dried for upto two years to attain the full depth of fragrance. I think you can assume it will be quite some time before I can reflect upon the outcome of my experiment!

  18. Yes, I have read that too, but in any case and for what is worth, I propose you do several batches of them: one marinating for 6 months, one for 1 year and the final one for 2 years and monitor the differences ~that should be fascinating!


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