Longevity is the property brands most want to claim and the one most often measured badly. The number a formula has depends entirely on what it was measured on: the same composition can last two hours on one person's skin, six hours on another, a day on paper and three days on a scarf.
This article compares the three substrates used in fragrance evaluation, explains how a panel is designed, and sets out how a longevity result should be reported so that it means something.
Three substrates, three different answers
Paper, skin and fabric give different and sometimes contradictory readings, and each answers a question the others cannot.
Paper shows the composition as designed. It does not interact chemically with the fragrance in the way skin does, it does not have a temperature of its own, and it does not produce the same mix of vapour. It is the fairest view of the formula and the least like the consumer's experience.
Skin is the consumer's experience and the least repeatable, because it varies between people and within the same person over a day. Fabric is where the fragrance is most persistent and where a brand finds out whether the product will mark clothing.
The practical implication is that a longevity figure without a stated substrate is not a measurement. When a brand asks for a number, the first question back should be what it was measured on. Our notes article covers how the three phases behave over time on each substrate.
Blotter: the fair view of the formula
A blotter is a strip of absorbent paper, and it is the tool the industry uses to evaluate a composition without the variability of skin.
Its advantages are real. Blotters can be labelled and compared side by side, an evaluator can return to the same strip over hours and days, and the absence of skin chemistry means the formula is judged on its own construction. Most development decisions are made this way for exactly those reasons.
Its limitation is equally real. Paper holds heavy materials and releases them slowly, so a composition evaluated on blotter always sounds longer and more base-heavy than the same composition on skin. A fragrance judged on paper as an eight-hour scent can be perceived as a three-hour scent when worn. Reading the blotter as a proxy for wear is the most common error in this kind of testing.
Skin: the reading the consumer gets
Skin is where the product is used, and its variability is a feature of the measurement rather than a problem with it.
Three variables dominate. The first is the oiliness of the skin, which affects how much of the composition is held in the surface film rather than released. The second is temperature, which rises with activity and with the ambient condition and directly accelerates evaporation. The third is moisture, which changes the solubility of some materials and can make a composition read differently after exercise or in humid weather.
On top of those sits the well-documented effect of the wearer becoming used to their own fragrance. A wearer will often report a scent as having disappeared while an evaluator standing nearby can still detect it. That is not a formulation problem and it cannot be tested away; it can only be accounted for by asking a second person to assess as well as the wearer.
The consequence for a development programme is that a longevity figure has to come from a panel rather than from one person, and the panel has to be described: how many people, what skin type, what room conditions and what activity level. Our scent strength article covers the same variables in a body-care product.
Fabric: tenacity and the damage question
Fabric testing answers two questions at once, and the second one is often more important than the first.
The first is tenacity: how long the fragrance remains detectable on a textile. Base-heavy compositions can persist through several days and sometimes through a wash, which is either a selling point or an annoyance depending on the positioning of the product.
The second is whether the product marks the fabric. Fragrance materials differ in their tendency to leave a stain or a ring, and the risk depends on the concentration, the colourant in the product and the type of fibre. A composition that performs beautifully on skin can ruin a silk blouse, and a brand that has not tested it will hear about it from customers rather than from a laboratory.
The standard approach is to prepare fabric swatches, apply a defined dose, allow them to dry, and then examine for both odour and visible residue over a defined period, including after a standard wash cycle. The results are reported per fabric type, because the answer differs between them.
Panel design: how many people and how long
A longevity panel is a small study, and it should be designed like one rather than assembled on the day.
The minimum useful size is usually in the range of twenty to thirty assessors, which is small enough to run in a normal evaluation facility and large enough to show a consistent trend rather than an individual's quirk. Fewer than that and a single atypical skin type can move the average.
The time points have to be fixed in advance. A typical design measures the intensity at application, at thirty minutes, and then at intervals through the day, with the interval tightening where the change is expected to be fastest. The assessment is normally carried out by a trained evaluator against a defined scale rather than by the wearer, with the wearer's own view recorded separately.
The conditions have to be stated. A panel run in a climate-controlled room at a stated temperature and humidity is comparable with another panel run the same way; a panel run wherever the assessors happened to be is not. If the product is intended for a hot market, the panel is often duplicated in a warm condition, because the difference between the two environments is larger than the difference between many formulations.
Instrumental options and where they run out
Instruments exist for fragrance measurement, and they are useful for specific questions while being unable to answer the main one.
Gas chromatography of the headspace above a sample can show which materials are present in the air at a given moment and at what relative amount. That is valuable for comparing two versions of a formula and for tracking a change over a shelf life, and it is repeatable in a way that a human panel is not. What it cannot do is say whether the composition smells good or whether it is still perceptible to a person, because perception is not a simple function of concentration.
There are also sensory instruments that measure odour intensity, and they are used in some laboratories. They are useful for a specific material or a specific question and they do not replace a trained panel for a complex composition.
The practical division of labour is that instruments establish comparability and panels establish perception. A brand that wants a defensible longevity figure normally needs both: the instrument to prove that two batches are the same, and the panel to establish what the product actually does.
How to report a longevity result
A longevity result is only usable if four things are stated alongside the number.
The substrate, because paper, skin and fabric give different answers. The conditions, including temperature, humidity and whether the assessor or the wearer made the judgement. The panel, including how many people and whether any were excluded. And the definition of the endpoint, which is the least standardised part: the point at which the fragrance is no longer detectable, the point at which it is no longer recognisable as the same composition, and the point at which a nearby person can perceive it are three different endpoints and they produce three different numbers.
Where a brand intends to print a duration on a pack, that number becomes a claim and the study behind it has to support the wording used. Our claims and testing article covers how a duration claim is assessed and what evidence is normally expected.
Substrate, what it shows and what it cannot show
| Substrate | What it shows | What it cannot show | Typical use |
|---|---|---|---|
| Blotter | The composition as designed, phase by phase | Wear on skin and consumer perception | Development and side-by-side comparison |
| Skin, wearer | How the product feels and fades to the user | Objectivity, because the wearer adapts | Consumer studies and preference work |
| Skin, trained assessor | Perceived intensity at defined intervals | One person's experience of many wearers | Panel-based longevity measurement |
| Sprayed fabric | Tenacity over days and after washing | Behaviour on skin | Tenacity claims and staining risk |
| Headspace analysis | What is in the air, and comparability of batches | Whether it is perceptible or pleasant | Batch comparison and shelf-life tracking |
| Warm-room panel | Behaviour at the temperature of the market | Behaviour in a cold climate | Products aimed at hot or humid markets |
The table describes the role of each method rather than a protocol. The number of assessors, the time points and the scales used depend on the market and on the claim the brand intends to make, and they should be agreed with the evaluator before the study starts.
What to put in the brief
- The substrate the brand wants the result on, stated explicitly.
- The endpoint definition: no longer detectable, no longer recognisable, or not perceptible to a nearby person.
- The temperature and humidity the panel will run at, and whether a second warm condition is needed.
- The panel size and the skin types to be included.
- The assessment points through the day, fixed before the study begins.
- Whether the wearer's own opinion is recorded separately from the assessor's.
- Whether fabric testing is included, and which fibres.
- Whether the result will be used in a claim, because that changes the required design.
Where our capability fits
We evaluate a composition on all three substrates and report which one each number came from. Blotter results are used for development decisions, skin panels for the wear, and fabric for tenacity and staining, and the conditions are recorded with the result so that a second batch can be compared with the first.
We work with brands on private label (your brand on a proven base), OEM/ODM contract manufacturing, and full custom formula development — whichever matches where your brand is today. Our fragrance work includes perfume and fragrance manufacturing and a gardenia-led floral, and the same evaluation method is applied to each.
Tell us what the number is for, and we will propose a study design and tell you what the result will and will not support. Start at our inquiry page, email capsulebiotech@163.com, or message the right team on WhatsApp: Capsule Series (capsules only) +86 158-7655-5319, Cosmetics Series (serum, hair care, body care, fragrance) +86 158-7655-5319.
General manufacturing information, not regulatory or legal advice. Test designs, acceptance criteria and claim requirements vary by market and by product type.