"Add some Iso E Super and it'll last" — that material's substantivity is 172 hours, and it may already be in there

One complaint in the "what annoys you" thread is very specific:

"The amount of shills around influencing people. I can't believe that there are so many sheep that have the idea that they can add a few common materials to a mystery perfume oil to magically transform the performance. Even after being advised by hobbyists and established perfumers, they are still convinced that's the case and we are keeping it a 'secret'."

A reply names the few common materials:

"It's always iso e super or ambroxan. I guess they think neither of those are already in there when it's likely that it's chock full of one or both."

This can be checked.

The short version

• The database gives Iso E Super (recorded as patchouli ethanone, CAS 54464-57-2) a substantivity of 172 hours at 100% and a strength of medium. Hexyl cinnamal reads 400 hours and so does isoeugenol. It is not a notably long-lasting material.
• It appears in 104 of 954 formulas (10.9%), Ambroxan in 31 (3.2%), and 122 (12.8%) contain at least one of them.
• The association is not there. Formulas containing Iso E Super hold 14.2% of their (data-covered) weight in materials lasting 300 hours or more; formulas without hold 14.1%. Effectively identical.
• The two get treated as one thing, and their doses differ thirtyfold. Corpus medians: Iso E Super 6.00%, Ambroxan 0.20%.
• And something nobody in the thread mentioned: this material has two environmental studies reaching opposite conclusions — one finding it far below the no-effect concentration and posing no ecological risk, the other finding it in receiving waters at 1.15 times a preliminary environmental threshold and in fish muscle and liver. The authors are differently affiliated.

About 9 minutes.

That material's substantivity

The numbers first.

	Iso E Super	For comparison
Database name	patchouli ethanone
CAS	54464-57-2
Substantivity	172 hours at 100%	hexyl cinnamal, 400 hours at 100%
Strength	medium
Suppliers	79
Occurrence	not found in nature
Odour	woody, dry, ambergris, cedar, old wood, ketonic, phenolic

172 hours.

That is a bit over seven days, which sounds long — and it is measured neat on a blotter, and it does not place near the top of the materials this series has covered. Calone reads >600 hours at 10% dilution, veramoss 400 hours at 10%, benzyl salicylate 384 hours at 100%.

Its strength is rated medium, not high.

So "add it and things last longer" starts from ground that is not especially firm. And adding to something already bottled is cheap while subtracting is nearly impossible.

(We've written about the two ways substantivity gets measured: records differ in dilution, so comparing raw magnitudes needs care. 172 hours at 100% against 400 hours at 100% is the same condition, so that comparison holds.)

The corpus shows no association

This part can actually be tested.

Matching the 954 public formulas against the database's substantivity field and keeping only those where at least half the weight matched a record (594 remain), the question becomes:

Do formulas containing Iso E Super differ from those without in how much weight sits in materials lasting 300 hours or more?

	Formulas	Median weight share, ≥300 hours
With Iso E Super	58	14.2%
Without	536	14.1%

A tenth of a percentage point apart.

This does not prove that adding it does nothing — it is an observational association rather than an intervention. A formulator choosing to include it is making many other decisions at the same time.

What it does remove is the easiest available support for the claim. If putting Iso E Super in genuinely reshaped a formula's longevity structure, some shadow of it should show up across 104 formulas, and none does.

(The Ambroxan group has n = 14 and a median of 9.6%. Too small; I am not going to read anything into it.)

12.8% of formulas already contain them

That commenter said the mystery oil is "likely chock full of one or both". The corpus can only speak for itself:

	Formulas	Share
With Iso E Super	104	10.9%
With Ambroxan	31	3.2%
With both	13	1.4%
With at least one	122	12.8%

One published formula in eight already has it.

And the corpus's vintage bias runs toward underestimating here. 74% of those 954 come from patents and published sources, and Iso E Super's use over the past two decades far exceeds what that literature reflects. The real share today can only be higher.

So the commenter's direction is right: what you want to add is probably already in there. And if it is already in there, you are adding "more", not "something new".

Those two are not the same thing at all

This matters more in practice than the longevity question.

They get named as one kind of booster, and their corpus doses differ by thirtyfold:

	Iso E Super	Ambroxan
Corpus appearances	104	31
Median dose	6.00%	0.20%
Strength	medium	high, recommend smelling at 1% or less
Substantivity	172 hours at 100%	> 400 hours at 10% dilution
Genre breadth	13/14, largest 30.5%	10/14, largest 25.6%

One goes in at a median of 6% and the other at 0.2%.

If someone tells you to "add a little Iso E Super or Ambroxan", the word "little" is thirty times bigger in one case than the other. Dose Ambroxan the way you would dose Iso E Super and you have ruined the bottle.

All they have in common is being described as woody amber and being very common. Every other column differs.

Incidentally: Molecule 01

From the same thread, at 39 points:

"Molecule 1 selling a bottle of iso e super for $125 lmao"

And underneath, better still:

"We use this super exclusive ingredient called hedione"

The joke works precisely because of what this piece has been saying: the material is ordinary, cheap and everywhere. Seventy-nine suppliers, and 13 of 14 genres in the corpus.

What comes next, though, is what nobody in that thread mentioned.

This material's environmental record has two opposite answers

Iso E Super goes by OTNE in the environmental literature. Following it up turns up two studies that disagree.

The first says no risk.

McDonough and colleagues measured OTNE in effluent and sludge at 44 US wastewater treatment plants in Chemosphere in 2017. Mean effluent concentration 0.69 ± 0.65 μg/L, sludge 20.6 ± 33.8 mg/kg dry weight. They used those distributions to predict surface water, sediment and terrestrial concentrations.

Their conclusion:

The probability of OTNE concentrations being below the predicted no effect concentration (PNEC) for the aquatic and sediment compartments was greater than 99%. For the terrestrial compartment, the probability was 97% under current US sludge application practices. … OTNE concentrations in US WWTP effluent and sludge do not pose an ecological risk to aquatic, sediment and terrestrial organisms.

The second says potential risk.

Klaschka and colleagues investigated 16 fragrances in five Bavarian sewage treatment plants and their receiving waters, in Environmental Science and Pollution Research in 2013.

Their result:

Only OTNE and HHCB were found in the receiving surface waters of the STP in congruent concentrations, which exceeded the preliminary derived environmental thresholds by a factor of 1.15 and 1.12 respectively, indicating potential risks. OTNE was also detected in similar concentration ranges as HHCB in muscles and livers of fish from surface waters and from ponds supplied with purified wastewater.

Their conclusion: the fate and potential effects of fragrance compounds in the aquatic environment deserve more attention.

How do two studies end up opposed?

At least four things differ:

1. Country and sample size. 44 US plants against 5 German ones.
2. Predicted versus measured receiving waters. The first predicts surface water concentrations from distributions; the second sampled the receiving waters directly.
3. Different thresholds. The first uses a PNEC, the second a "preliminary derived environmental threshold", and a factor of 1.15 is highly sensitive to which threshold you pick.
4. The authors are differently affiliated. McDonough's co-authors are from Procter & Gamble, IFF and RIFM; Klaschka's are from Ulm University of Applied Sciences and the Bavarian Environment Agency.

I write the fourth point down without accusing anybody. Industry-funded work can be done well, and McDonough's measurement programme (44 plants) is far larger than Klaschka's. I write it because readers are entitled to know, and because neither paper hides it.

We've written about reading safety studies, and this pair is a clean demonstration: two real studies, both with measured data, opposite conclusions. The move is not to pick a side; it is to write down the conditions on both.

Collecting it up

• "Add one material and it lasts" finds no support in the corpus, and the material in question reads 172 hours at medium strength.
• It is probably already in there — one published formula in eight.
• Iso E Super and Ambroxan are not synonyms; their doses differ thirtyfold.
• To change longevity, change the ratio among your top three rather than adding an eighth material.
• And the genuinely interesting thing about this material is not its price. It is that its environmental record has two opposite answers.

What this doesn't establish

The corpus analysis is observational, not experimental. The 14.2% against 14.1% says formulas containing it do not differ in long-substantivity weight structure from those that do not. It does not say "adding it changes nothing". Answering that needs the same formula with and without, which is not in the corpus.

Only 594 formulas were usable (the rest had materials with no substantivity record), and the Iso E Super group is 58. 58 against 536 is a large imbalance, and the small group's median is unstable.

Substantivity values come from inconsistent measurement conditions. Some neat, some at 10% dilution, as covered elsewhere. In the body I compared only within one condition (100% against 100%).

I have no idea what is in any commercial fragrance oil. The corpus's 12.8% is a share of published formulas, not of products on sale, and the commenter was talking about products on sale.

The Ambroxan group is n = 14 and I did not interpret it. That 9.6% should not be quoted.

I did not read the full text of McDonough's paper to see how the PNEC was derived. The abstract gives only the conclusion. The disagreement may turn largely on threshold derivation, and I cannot judge that from abstracts.

Klaschka's factor of 1.15 is very close to 1. That means the conclusion is sensitive to both the threshold and the sampling moment, and the paper itself says "potential risks" rather than "risks".

Both studies are roughly a decade old. Usage and treatment technology both change, and I have not looked into the current situation.

I have smelled neither Iso E Super nor Molecule 01. I am only relaying that joke.

References

K. McDonough, K. Casteel, A. Zoller, et al., Probabilistic determination of the ecological risk from OTNE in aquatic and terrestrial compartments based on US-wide monitoring data, Chemosphere, 167, 255-261 (2017). PMID 27728884. doi:10.1016/j.chemosphere.2016.10.006

U. Klaschka, P. C. von der Ohe, A. Bschorer, S. Krezmer, M. Sengl, M. Letzel, Occurrences and potential risks of 16 fragrances in five German sewage treatment plants and their receiving waters, Environmental Science and Pollution Research International, 20(4), 2456-2471 (2013). PMID 22945655. doi:10.1007/s11356-012-1120-9

Related: Iso E Super, what makes a workhorse, how to read fragrance safety studies, two ways of measuring longevity.