Joining fifteen articles into one path: from a new material to a formula you can hand over

The previous fifteen articles each solved one problem. This one joins them together, and then says plainly where the path leads and where it does not.

When a new material arrives

Six stages. Each step is tagged with the article it comes from.

1. Receiving (five minutes, on the day)

1. Decant into two or three small bottles, each filled right to the top. The volume of headspace air sets the oxidation rate directly. (Storage)
2. Keep a retain of 1–2 mL, sealed and refrigerated. It is the only baseline you will ever have. (Batch variation)
3. Label: material, supplier, batch number, delivery date, and the date you opened it, which is the one everyone forgets. Copy the batch number in full; it is part of the material's identity. (Batch variation, Storage)
4. Record the purchase: unit price and unit, minimum order, total paid including freight, date of the quotation. (Cost and sourcing)

Under five minutes, and it decides whether that bottle becomes trustworthy data or a question mark.

2. Getting to know it (first week)

5. Look up the recommended dilution before diluting. 10% is the default, but nearly a third of materials need to be weaker. Evaluate a material that belongs at 0.1% at ten percent and all you get is "harsh, no detail". (Solvents)
6. Make the dilution in DPG, weighing both components, recording the actual grams, and labelling the concentration you actually achieved. (Weighing, Solvents)
7. Cover the label before smelling. When you know what you are smelling, part of what you smell is what you expect. The first time I smelled blind I filed a material I had used for ages into the wrong family, and I have not skipped this step since. (Record keeping)
8. Five time points: 0 / 15 min / 1 h / 4 h / 24 h, with three to five descriptors at each, chosen only from your fixed list. (Record keeping)
9. Write one line about what it could do. "Smells lovely" tells future-you nothing; "clean woody base, could hold up the tail of a citrus" will still mean something in six months. (Record keeping)

3. Placing it in context (first month)

10. Compare it beside materials you already know. Interleave families, 8 to 12 per session, and re-smell the first at the end to calibrate yourself. (Olfactory fatigue)
11. Locate it: where it sits on the evaporation curve, and roughly what order of magnitude its strength is. Treat the curve as continuous; top-middle-base is a convenience of speech. (Odour thresholds, Evaporation curves)

4. Making a formula

12. Start with three materials. Three to four components is the practical limit of olfactory identification, and it binds experienced noses just as tightly. (First accord)
13. Percent by weight, summing to 100. Drops are unreliable: drop volume varies ninefold even across purpose-made pharmaceutical droppers. (Weighing)
14. Serial dilutions for traces, keeping the balance in its comfortable range, and count the solvent in the total. (Weighing)
15. Add low-volatility materials early. A gap in the middle of the curve cannot be filled by bolting a weight onto the tail. (Evaporation curves, Fixation)
16. Decide what you want left at the end. By hour eight, what you are smelling is simply your most tenacious component. (Fixation)

5. Verifying

17. Remake it. Rebuild from your notes; if you cannot produce the same thing, the notes are what needs fixing.
18. Assess it in the finished product's solvent. A formula balanced in DPG reorders itself in ethanol. (Solvents)
19. Blind test with five to eight people, randomised order. Ask for descriptors; on preference, allow one question only: "would you want to smell it again?" (Individual differences)
20. Record the 24-hour point. Those three to five descriptors are what the formula actually leaves behind. (Fixation, Storage)

6. Handing it over

21. The formula sheet: percent by weight, the masses actually weighed, supplier and batch for each material, solvent and concentration.
22. Regulatory check: if it goes on skin or to another person, consult the current IFRA Standards. A material appearing in the register does not mean it is restricted. (IFRA limits)
23. The cost sheet: dose times price, sorted. Two or three materials will be deciding the total. (Cost and sourcing)

A formula is ready to hand over once you can fill in all twenty-three of those fields.

How big is the realistic starting point?

The first article said to buy ten materials. Ten out of how many?

Filtering the database from the top:

Filter	Remaining	Retained
All materials in the database	42,225	—
With supplier records	21,494	50.9%
+ with an odour description	5,824	27.1%
+ at least three descriptors	4,438	76.2%
+ carried by a small-quantity retailer	1,349	30.7%
+ present in the IFRA register (rather than flavour-only)	1,244	92.2%

From 42,225 to 1,244: 2.95% survives.

How to read this. "Small-quantity retailer" counts only the 8 we could positively identify in the supplier list, so that step is a lower bound and the true figure is higher. And "present in the IFRA register" means only that the material appears there — it does not mean the material is restricted, a trap the IFRA article walked into and out of. It is used here as a proxy for "belongs to the perfumery market rather than the flavour market", not as a safety judgement.

Even so, the direction is clear: your actual working palette is on the order of a thousand-odd materials. Forty thousand is the size of the whole catalogue, and you were never going to face the whole catalogue. A thousand-odd is a scale one person can hold, which is good news. The ten from the first article come from that pool.

What this path cannot give you

Here is where the series owes you honesty.

In 2013 Royet, Plailly, Saive, Veyrac and Delon-Martin reviewed research on olfactory expertise in Frontiers in Psychology. Three findings are worth quoting as written:

Training demonstrably works on the untrained.

Until the 21st century, only the behavioral effects of olfactory training of untrained control individuals had been reported, revealing an improvement of olfactory performance in terms of sensitivity, discrimination, memory, and identification.

But the behavioural evidence on experts themselves is not settled.

Behavioral studies of odor experts have been scarce, with inconsistent or inconclusive results.

What is distinctive about experts is odour mental imagery.

Researchers have particularly focused on odor mental imagery, which is characteristic of odor experts, because this ability is absent in the average person but is part of a perfumer's professional practice.

The same review notes that brain imaging shows functional and structural modification with experience: perfumers show lower activation in the piriform cortex and hippocampus during imagery tasks. Same job, less effort.

Putting those together, the honest summary is:

• Trainable: discrimination, memory, identification, naming, and eventually odour imagery.
• Unsettled: whether an expert's nose outperforms on basic sensory tests. The literature does not support that consistently.
• So this series teaches method. Method makes your judgements repeatable, your formulae reproducible, and your notes readable in six months. That is only part of the craft, but it is the part you can acquire by reading.

Two further limits:

Our data is a catalogue. It can tell you what a material is, who sells it, how long it keeps; what to combine is beyond it. Everywhere this series cited its own data, it was answering "what shape is this field". What you should make was never in the data.

Sixteen articles do not replace one evaluation session. That sounds like a platitude but it has a concrete meaning: of the twenty-three steps above, only steps 21 to 23 can be completed at a desk.

But one thing is definitely learnable

The recommendation that recurs most often in this series is to build a fixed vocabulary. The evidence behind that advice is strong, and it comes from an unexpected direction.

In 2014 Majid and Burenhult tested, in Cognition, a claim repeated from Plato to Pinker: that smells cannot be put into words.

They point out that decades of studies had indeed confirmed the observation. The catch is the sampling: those studies used participants from urbanised Western societies. Among the Jahai of the Malay Peninsula, odours play a larger role.

Using a free naming task we show on three different measures that Jahai speakers find it as easy to name odors as colors, whereas English speakers struggle with odor naming. Our findings show that the long-held assumption that people are bad at naming smells is not universally true.

The paper's title is its conclusion: odours are expressible in language, as long as you speak the right language.

For a beginner the implication is immediate. You cannot describe that smell not because your nose is inadequate, but because you lack the vocabulary. And vocabulary can be built. The Dravnieks study cited in the record-keeping article used a fixed list of 146 descriptors to get highly reproducible profiles from about 150 subjects.

A fixed vocabulary supplies the piece your language is missing.

What to do next

The reading is done. What comes next is accumulating records.

Concretely, over the next three months:

1. Buy the ten materials from the first article, chosen by the cost article's standard: ten you will still be able to buy in six months.
2. Run stages 1 and 2 above on each: decant, retain, date, dilute to 10% or the recommended concentration, five time points, fixed vocabulary. Ten materials, ten complete records.
3. Build your own list of 30 to 50 descriptors and use only what is on it. When nothing fits, record the failure to find a word. That is information too.
4. Make three three-material formulae, in percent by weight, recording the actual masses, and rebuild each from its notes a week later.
5. After three months, re-smell the first material against its retain. At that point you learn two things at once: how much that bottle changed, and how much you did.

Step 5 is the real end of this series. Your first batch of records is not useful yet; the value arrives once there is a second batch to compare against. Which is exactly why you start recording today rather than once you "know more".

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Everything this series teaches reduces to one sentence: record what you did in enough detail that your future self can reproduce it. Dilution, weighing, vocabulary, retains, batch numbers, blind tests: all facets of that one thing. The rest is smelling.

References

A. Majid & N. Burenhult, Odors are expressible in language, as long as you speak the right language, Cognition, 130(2), 266–270 (2014). PMID 24355816

J.-P. Royet, J. Plailly, A.-L. Saive, A. Veyrac & C. Delon-Martin, The impact of expertise in olfaction, Frontiers in Psychology, 4, 928 (2013). PMID 24379793

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This is the final article in the Beginner perfumer series. The order of the sixteen is the recommended reading order, and this one is meant to be returned to as a checklist.