A fragrance is not a fixed thing. It moves. What rises from skin in the first minutes is a different proposition from what remains there after lunch, and different again from the trace left on a sleeve by evening. Most people judge a scent on first contact and never meet the rest of it.
This is worth correcting, because first contact is the least representative moment a fragrance has.
Three speeds, one composition
Perfumery organizes scent into a rough structure of top, heart, and base. The terms are not poetic, they describe volatility, which is to say how quickly a molecule lifts off the skin and reaches the nose.
Top notes are the lightest and fastest. Citrus, light herbs, the brighter florals. They announce themselves immediately and leave almost as quickly, fifteen to thirty minutes, often less. The bergamot in an opening is doing precisely this work: arriving loud, then stepping back. Its character, discussed at greater length here, is bright, green-edged, slightly bitter, and largely gone before the half hour is out.
Heart notes hold the middle. Fuller florals, spices, fruits, certain green materials. These carry the body of the fragrance for roughly two to four hours. This is the stretch most people actually live in, though it is rarely the stretch they smelled in the shop.
Base notes are the slowest and heaviest. Woods, resins, musks, ambers. They can linger eight to twenty-four hours, sometimes longer on fabric. They are also the foundation everything else was built on, the part that decides whether a fragrance reads warm or cool, dry or soft, once the brighter material has burned off.
What the dry down actually is
The dry down is what a fragrance becomes once the volatile material has gone and the base is left to speak alone. It is the most honest version of a scent, in the sense that it is the one you spend the most time wearing.
A fragrance can open beautifully and dry down to something flat or cloying. Another can open quietly, almost unremarkably, and settle into something far better an hour in. Judging by the opening alone means judging by the part designed to disappear. The green snap of crushed galbanum and similar materials is a good example: striking at first, then yielding the stage entirely to whatever sits underneath.
This is also why a scent that seemed wrong at the counter can seem right by the time you reach the car, and why the reverse happens just as often. The composition kept moving. You simply met it at one point and assumed that point was the whole.
Why your skin matters
The same fragrance does not behave identically on two people. Skin temperature, oiliness, and pH all influence how quickly volatile molecules lift and how the base holds. Warmer, oilier skin tends to project more and hold longer. Drier skin can burn through the top and heart faster, arriving at the base sooner.
This is part of why the idea of a single defining scent is harder to pin down than it sounds, a point worth its own consideration. The fragrance is one half of the equation. The skin it sits on is the other.
It is also why describing a scent to someone else is so unreliable. The word you reach for at minute two may not apply at hour three, and the vocabulary itself tends to fail before the fragrance does. The seven fragrance families help organize a first impression, but as is noted elsewhere, scents rarely stay inside their assigned family, partly because their character shifts as they evolve. A citrus that dries down to wood has, by the end, become a woody fragrance in every meaningful sense.
Soap runs the same arc, compressed
Fragrance in soap follows the same logic, but on a far shorter timeline, and under unfavorable conditions.
In lather, the top notes have almost no chance. Heat, water, and the brief contact time of washing strip the lightest material away before it can register fully. What you smell over a basin is mostly an accelerated rush of top and heart, then nothing, because the whole thing is rinsed off in under a minute.
What stays on skin afterward is closer to the base. The heavier woods, resins, and musks are the molecules with the staying power to survive the rinse and remain on warm, clean skin. So the scent of a soap in the shower and the scent it leaves on the skin an hour later are two different impressions, and the second is usually the more accurate one. A bar that smells sharp and citric under water may settle into something quieter and woodier once dry, the same compression of the same arc, run in minutes rather than hours.
This is the practical reason to pay attention over time rather than on first sniff. The opening is information, but it is partial. Give a fragrance the hour it asks for. Smell it again when the bright material has burned off and the base is doing the work alone. That later impression, slower, steadier, less eager to please, is the one you will actually wear.