"I can't smell it" — five reasons, two of them arithmetic and one written in a gene

Someone posted a photo on r/DIYfragrance with a direct question:

"Is Orris Butter (10% in TEC) supposed to look like this?"

He added: it is the first time he has seen or smelled it; he is working through all his materials assessing them at intervals, and this one is listed as a base material and he could not smell it after 30 minutes. It also looked a little too thick for something already diluted at 10%.

Twenty-one replies offered five explanations. Two of them are arithmetic and one is written in a gene.

The short version

• The appearance question has a clean answer. Orris butter (Iris pallida rhizome concrete) melts at 40-46 °C — solid at room temperature, liquid only above body heat. The first reply in the thread got it right.
• The biggest reason he could not smell it is arithmetic. He has a 10% product, diluted to 1% for evaluation, which is 0.1% orris butter. Orris butter's own irone content is what suppliers state: 8% to 15%. So he was smelling roughly 0.015% irone — 150 ppm.
• The most careful comment in the thread was off by more than tenfold. It assumed the 1% was a dilution of neat butter, when the 1% was of a 10% product.
• The database rates orris butter's odour strength as low. That is part of the answer on its own.
• Why it is both thick and weak has one cause: a 2024 study compared headspace with hydrodistillation on iris rhizomes and found that the hydrodistillate's main component was docosane at 45.79%, with fatty acids, while irone dropped from 43.74-45.76% in headspace to 24.70%.
• Two people in that thread report opposite experiences of beta-ionone. That is not coincidence: a 2013 study identified rs6591536 in OR5A1 as explaining more than 96% of the variation in beta-ionone sensitivity, resembling a Mendelian trait.

About 9 minutes.

Appearance: the melting point is the answer

The first reply is a good one:

"Why you think it's gone bad? … This is completely normal. Orris butter is a solid at room temperature, even diluted in tec. Just keep it in your pocket and you'll see it turn liquid again. Orris butter doesn't 'go bad'. It actually ages very nicely over the years."

The database agrees.

	Value
Name	orris rhizome concrete butter (Iris pallida)
CAS	8002-73-1
Melting point	40-46 °C
Appearance	pale yellow to yellow paste
Odour strength	low
Suppliers	40

Forty to forty-six degrees, which is above body temperature.

We ran the numbers in the white particles piece: of the 460 database materials with 20+ suppliers and a melting point, 255 (55.4%) are solid above 20 °C. Orris butter is among the highest of that group.

"Keep it in your pocket" is the right advice — the same as step two in the white particles piece: warm it toward body temperature and see whether it melts.

(The poster mentions a previous bourgeonal that went solid. The reply got that right too: it is an aldehyde and can polymerise and turn solid, especially neat. We wrote the same thing in the phenylacetaldehyde piece — that material's three-month shelf life has exactly this cause.)

The smelling question: do the arithmetic first

This is the heart of the piece, because it is the most commonly miscalculated step.

The poster wrote: "I already diluted it at 1% which is where I assess most of my materials."

And the product he bought was already at 10%.

So:

Step	Actual orris butter concentration
The supplier's product: 10% in TEC	10%
Diluted to 1% for evaluation	0.1%
Irone within the butter (suppliers state 8-15%)	0.008%-0.015%

Eighty to one hundred and fifty parts per million.

The most careful comment in the thread reads:

"Let's take your orris butter as an example: it contains 20% irones. By diluting the material at 1%, you end up having a 0.2% solution of irone (+ all the other stuff, some of which can be very faint), which is not really that much."

The direction is exactly right, and the number is off by more than tenfold.

Because that assumes the 1% is a dilution of neat butter. The poster's product was already 10%, so the real figure is 0.015%, not 0.2% — about thirteen times apart.

This is not nit-picking. It is the arithmetic this hobby most often gets wrong, and when it goes wrong it usually goes wrong by a whole order of magnitude. We've written about weighing and dilution, and this is its most practical instance:

"I diluted it to 1%" means something only when you know what you started from.

The database says its strength is low

This is the second checkable reason, and it is quick.

Material	Strength	Substantivity
orris butter	low	—
alpha-irone	medium, recommend 10% or less	104 hours at 100%
beta-ionone	medium, recommend 10% or less	112 hours at 100%

The butter is low, and pure irone is medium.

Put the two together: a material already labelled low, diluted to a thousandth of itself. Gone in thirty minutes needs no further explanation.

One commenter said "30 minutes is about right for orris butter", which is consistent with this.

Why it is thick and weak for the same reason

This is the most interesting part.

Friščić and colleagues compared volatiles from three endemic Croatian irises in Molecules in 2024, using headspace solid-phase microextraction and hydrodistillation.

On the oldest, irone-rich Iris pseudopallida sample:

Method	cis-α-irone	Main component
Headspace (HS-SPME)	43.74-45.76%	irone
Hydrodistillation (HD)	24.70%	docosane at 45.79%

The same rhizome. Change the sampling method and irone drops from 44% to 25%, while the main component becomes a C22 alkane.

The paper adds that hydrodistillation yielded predominantly fatty acids — myristic (present in all samples, 4.20-97.01%), linoleic (40.69%) and palmitic (35.48%).

That explains two things.

First, why orris butter is solid. Myristic acid melts at 54 °C and palmitic at 63 °C. This is not "a fragrance material containing some wax"; it is a mass of fatty acids with the thing you want inside it. The 40-46 °C melting point is those fatty acids' melting point.

Second, why suppliers sell you a content rather than a material. The database's fields carry the manufacturers' product names: "ORRIS BUTTER ABSOLUTE 15%", "Orris Concrete Nat 15% Irone", "Orris butter reinforced 8% Blend".

When you buy orris butter, what you buy is that percentage. Two bottles both called orris butter can differ twofold in irone.

To be clear: Friščić measured three endemic Croatian irises, not commercial Iris pallida orris butter, and neither headspace nor hydrodistillation is how orris butter is made. I cite it for the order of magnitude of "an iris rhizome extract is mostly fatty acids with irone as a minority", not for any product specification.

That exchange is a gene

One exchange in the thread stopped me.

Mammoth-Trip-4522:

"For me, ionone beta is difficult to smell, but it has a noticeable airating effect on woody base notes and patchouli."

The poster's reply:

"ionone beta is pretty strong for me, but it could also be that I have the same for orris that you have for ionone beta right?"

He guessed right, and there is a very clean study of it.

Jaeger and colleagues studied β-ionone in Current Biology in 2013, because it "shows extreme sensitivity differences".

Their result:

Genome-wide and in vitro assays demonstrate rs6591536 as the causal variant for β-ionone odor sensitivity. rs6591536 encodes an N183D substitution in the second extracellular loop of OR5A1 and explains >96% of the observed phenotypic variation, resembling a monogenic Mendelian trait.

More than 96%. That is extraordinarily clean for human sensory variation.

And the consequences go beyond whether you can smell it:

Individuals carrying genotypes for β-ionone sensitivity can more easily differentiate between food and beverage stimuli with and without added β-ionone. Sensitive individuals typically describe β-ionone in foods and beverages as "fragrant" and "floral," whereas less-sensitive individuals describe these stimuli differently.

Note that last clause. Less-sensitive people are not simply failing to smell it. They are describing the same thing with different words.

Which joins up with the naming problem from an earlier piece: when four people describe one material four ways, it can be a language problem — and it can be that they are genuinely smelling different things.

The poster's guess — that his orris might be his correspondent's beta-ionone — is a reasonable hypothesis, and I have to flag that the study measured β-ionone, not irone. The two are structurally close, and I found no matching study for irone. That guess currently has neither evidence for it nor against it.

So what concentration should you evaluate at

The thread contains an argument about this worth recording.

The poster's practice: most materials at 1%, keeping softer or high-dose things like Iso E Super, Hedione and lemon oil at 10%.

The other view (quodo1):

"Most materials benefit from being evaluated at 10%, 1% for stronger ones and 0.1% for nuclear stuff."

Both have a rationale, and the difference is what you want to learn.

• A fixed concentration (the poster's 1%) lets you compare strengths across materials.
• Adjusting by strength (quodo1's three tiers) puts every material in a range where you can hear it.

And this thread demonstrates the fixed-concentration failure mode: a material labelled low, already sold as a 10% product, comes out at nothing at 1%.

A compromise is to use the database's strength label as the tier. We showed the strength labels match real dose levels: high sits at a median dose of 0.80%, medium at 2.00%, low at 5.78%. That ladder works as an evaluation-concentration ladder too.

Collecting it up

"I can't smell it" has five common causes, and they need different handling:

Cause	How to tell	What to do
Arithmetic (dilution of a dilution)	Re-read the product label	Recalculate
The material is simply weak	Check the strength field	Change concentration or accept it
Olfactory adaptation	Leave the room, wait hours	Wait
Too concentrated, causing fatigue	Dilute further and retry	Try 0.1%
You cannot smell this one	Others can and you cannot	Accept it and borrow a nose

The first two can be worked out before you order. The other three need experiments.

And the one thing the poster got right is that he wrote down the times:

0000: Soft, earthy, powdery and floral. Also has a note that reminds me of raw potato peel. 0005: Less earthy, just soft, powdery and floral. Potato peel has gone. 0015: Overall a lot more faint, similar scent profile. 0030: Can't smell it anymore.

Those notes are more useful than this entire article, because they are data his own nose produced at his own concentration. We've written about keeping evaluation notes.

What this doesn't establish

I have not seen the photo and have smelled none of these. All of it is written against a text description, database fields and two papers.

The dilution arithmetic rests on two assumptions. First, that "diluted it at 1%" means diluting the 10% product to 1% — his words could mean something else. Second, that the 8-15% irone content, read off manufacturer product names in the database fields, is not the specification of his bottle. If either assumption is wrong the numbers change.

"That comment was off by more than tenfold" is about the calculation in that comment, not about the person's judgement. Their conclusion — that the concentration was too low — is correct, and they were the only person in the thread who did any arithmetic at all.

Friščić measured three endemic Croatian irises (I. pseudopallida, I. illyrica, I. adriatica), not the commercial Iris pallida cultivars orris butter is made from, and used headspace and hydrodistillation, neither of which is how orris butter is produced. Those percentages describe those samples and cannot be read as orris butter specifications.

The myristic acid range of 4.20-97.01% is enormously wide, reflecting differences between three species and three methods. I cite it for the qualitative observation that hydrodistillation yields predominantly fatty acids.

Jaeger measured β-ionone, not irone. Flagged in the body and repeated here: extending it to irone has no evidence behind it.

">96% of phenotypic variation" is their result in their study population. Allele frequencies differ between populations, so that proportion need not hold elsewhere.

The evaluation-concentration section has no research behind it. It is two commenters' practices plus my own suggestion derived from the strength ladder, not a validated method.

References

S. R. Jaeger, J. F. McRae, C. M. Bava, et al., A Mendelian trait for olfactory sensitivity affects odor experience and food selection, Current Biology, 23(16), 1601-1605 (2013). PMID 23910657. doi:10.1016/j.cub.2013.07.030

M. Friščić, Ž. Maleš, I. Maleš, et al., Gas Chromatography-Mass Spectrometry Analysis of Volatile Organic Compounds from Three Endemic Iris Taxa: Headspace Solid-Phase Microextraction vs. Hydrodistillation, Molecules, 29(17), 4107 (2024). PMID 39274954. doi:10.3390/molecules29174107

Related: orris butter, white particles in the bottle, weighing and dilution, individual differences.