What aldehydes actually do
Half a milligram changes the whole opening. Nine aldehydes in the library, not one of them working above 0.4 per cent, and none of them smelling of anything you could name.
Half a milligram of Aldehyde C-10 decanal in ten grams of concentrate is 0.005 per cent, one part in twenty thousand. That is the bottom of its published working window, and you will smell it. This is the whole difficulty with aldehydes, and it is arithmetic rather than mystery.
Look at what else is on the sheet. Hedione works from 2 to 40 per cent. Iso E Super, 2 to 40. Galaxolide, 2 to 30. Aldehyde C-10 decanal stops at 0.4. You are being asked to dose one line of the formula two orders of magnitude below the line above it, on the same scale, in the same session.
What the numbers say
| Volatility | Impact | Blotter hours | Working dose | |
|---|---|---|---|---|
| Aldehyde C-8 octanal | 92 | 7.5 | 1.5 | 0.01–0.3 % |
| Aldehyde C-9 nonanal | 90 | 7.5 | 2 | 0.01–0.3 % |
| Aldehyde C-10 decanal | 86 | 8.5 | 2 | 0.005–0.4 % |
| Aldehyde C-11 undecanal | 86 | 7 | 3 | 0.01–0.3 % |
| Aldehyde C-11 undecylenic | 84 | 8.5 | 2.5 | 0.005–0.4 % |
| Aldehyde C-12 MNA | 82 | 8.5 | 3 | 0.005–0.35 % |
| Aldehyde C-12 lauric | 82 | 7 | 4 | 0.01–0.3 % |
| Methyl nonyl acetaldehyde | 82 | 7 | 3.5 | 0.01–0.3 % |
| Adoxal | 76 | 8 | 4 | 0.005–0.35 % |
That is the whole aldehydic family in the Crafted Scent library. None of the nine carries an IFRA category 4 limit, which is the one easy thing about them. Cold-pressed lemon, at odour impact 4.5 and a working dose of 1 to 10 per cent, is restricted to 2. The gentle material is the regulated one; the one you weigh in milligrams is not.
Why a fraction of a per cent is enough
Two columns explain it. Volatility 76 to 92 puts all nine in the top note, which is where the studio classifies them, because none of them holds long enough for tenacity to pull it lower. So whatever they do they do to first impressions. Impact 7 to 8.5 is the other half: at 8.5, three of them register strongly at a dose where most of the bench is silent. Volatility decides when your nose meets a material. Impact decides how little has to be there.
The hours column is the surprise. Those are blotter hours, and skin releases the same oils roughly twice as fast, so halve them for a wrist. Even halved, C-12 lauric and Adoxal are still working at two hours. Lemon is 0.8 hours on the blotter. That is why an aldehydic opening does not fall off the cliff a citrus one falls off.
Why they read as soap and wax
Read the library's own facet words. Eight of the nine are described with waxy or fatty; three say soapy outright. The flowers that do appear sit on top of the wax rather than instead of it: rose on C-9 nonanal, rosy and metallic on C-11 undecylenic, violet on C-12 lauric. Adoxal is the only one that escapes the wax entirely, and it goes marine instead.
Those are texture words, not objects. Nothing in the list is a thing you could point at, which is exactly why an aldehyde does not read as its own smell in a finished perfume. It reads as a condition the other materials are in. Scrubbed. Pressed. Just off the line.
How to dose them without wrecking a perfume
Start at the published minimum. In a ten gram batch, 0.005 per cent is half a milligram and 0.01 per cent is one milligram. No bench scale weighs that honestly. Weigh a 10 per cent solution instead: one milligram of material becomes ten milligrams of liquid, which reads as 0.010 g on the display. This is the clearest case on the bench for keeping everything at ten per cent, and the plainest reason drops will not do.
Spread them across the volatility column. The nine cover sixteen points of volatility and two and a half hours of blotter life, and that spread is the part worth using. C-8 octanal, at volatility 92 and 1.5 blotter hours, is finished first. C-12 lauric, at 82, runs to four. Take one from each end and the effect arrives in stages rather than as a single burst, which is a different move from dividing one dose among three materials that all behave alike.
Then stop. Past roughly a tenth of a per cent in total, in our hands, the soap stops being a quality of the opening and becomes the subject of it. The top of the published window is for an accord that wants to be an aldehydic, not for a formula that wants lift.
Put Aldehyde C-11 undecanal in a formula at 0.3 per cent and read the timeline. Then take it to 0.03, a tenth of the dose, and read it again. The opening does not lose a tenth of anything. Watch instead for which other materials suddenly become audible, because that is the real cost of an overdosed aldehyde and it never shows up as soap.
Open the bench →Two things called aldehyde that are not
Aldehyde C-14 peach is gamma-undecalactone wearing a trade name. The library files it under gourmand, working dose 0.05 to 1.5 per cent. Aldehyde C-16 strawberry is ethyl methylphenylglycidate, filed under fruity, same window. Both are several times more generous than the real aldehydes and neither does anything aldehydic. If the name has had you treating them as trace materials, you have been underdosing them.
IFRA revises its standards. The limits above are what the studio library holds today, and the bench applies them at the category you have chosen in its Compliance panel. Before a formula leaves your hands, check the current standard rather than a journal post, including this one.