muihuong.vnScent keeps what you forget.
Menu
Tiếng Việt

Learn · Part One — Learning to smell · Lesson 7 of 9

Concentration decides the nature of a smell, not just its strength

The same molecule can be white flowers at one dose and faeces at another. This is the most counter-intuitive fact in all of smell.

With colour, diluting only makes the colour paler. Diluted red is still red, just pinker.

With smell it is not like that. Dilution can change the very nature of a smell.

The clearest example

Indole at high concentration smells of faeces. At low concentration it gives a warm white-flower sensation, leathery, and almost indispensable.

That indolic layer is exactly what sets jasmine apart from every other white flower. Take it away and what remains is an anonymous sweetness that any cheap synthetic fragrance can produce.

People smelling real jasmine for the first time often say it is a little dirty. They are right. And that dirtiness is precisely what gives it value.

Three more cases

Butyric acid at high concentration is rancid butter and sweat. At very low concentration it gives a pleasant sense of richness, and it is present in many well-loved cheeses.

Milkwood flower is suffocating beneath the tree and pleasant fifty metres downwind. One tree, one night, two opposite verdicts — and that is why a row of trees can become a subject of public dispute.

Almost nobody can bear fermented shrimp paste smelled straight from the bowl. Put a little on a plate, wait a minute for it to thin, then smell from two hand-spans away — the three layers separate and you catch the deep umami layer at the bottom, something smelling up close never reveals.

The technique

Dilution is an analytical tool, not a way of avoiding things.

It is the standard technique in every sensory evaluation room, and it runs against instinct. Instinct tells you to bring it close to smell it better; technique tells you to step back and dilute.

With a strong sample, put a drop on a smelling strip and wait a minute. With a dense liquid, dilute one drop in ten drops of carrier oil. With a smell in a space, change your distance and note it at three positions.

Why this matters

It explains why two people can argue fiercely about a smell and both be right — they are smelling at two different concentrations.

It also explains why a composition analysis does not tell you how a bottle of essential oil smells. The list of components tells you what is present; the experience depends on how much, and the relationship between the two is not linear.

From this comes a rule for reading: on a chromatogram, the horizontal axis can be trusted, while the vertical one needs care.

Further reading for this part

A shared list for the whole of Part One — Learning to smell, not a note for every sentence. We state what each source was used for.

  1. Asifa Majid and Niclas Burenhult, 2014. Odors are expressible in language, as long as you speak the right one A study of the Jahai of the Malay Peninsula, a group with an abstract smell vocabulary. It underpins the central argument of Part One: the gap lies in vocabulary, not in the nose.
  2. Caroline Bushdid et al., 2014. Humans can discriminate more than 1 trillion olfactory stimuli The trillion figure is widely quoted. We cite it together with its critique, because Meister (2015) and Gerkin and Castro (2015) showed problems with how it was extrapolated. It is our example of how an attractive number can spread without anyone checking it.
  3. Những cây thuốc và vị thuốc Việt Nam A Vietnamese-language source for the species names, parts used and sensory descriptions of most of the medicinal plants in the dictionary. Where it and other literature disagree — as with garden mint — we give both.

One thing must be said plainly. We have not read every work above in the original; most of the knowledge comes through secondary literature and reviews. We say so rather than let the list suggest a depth of research we have not reached.

Last updated: September 2026