As with wine, cheese or music, greatness in perfume often means complexity.
If you regularly wear perfume, it should come as no surprise that your favorite scent unfolds in stages. The way you smell immediately after applying it, and then 20 minutes later and then 40 minutes later can be quite different, and this is by design. The people who created that scent chose its ingredients, which are basically essential oils, not only by their individual and combined aromas but also based on their relative evaporation rates.
The changing character of a perfume comes from the varying volatility of scent molecules. When you spray or dab on a fragrance, the first thing you smell is the combined effect of all of the scents in the product. Then, as some of those scent molecules evaporate and others stick around, the fragrance starts changing. Eventually, what you're left with is the scent of the longest-lasting, or least volatile, of the scent molecules included in your perfume -- and this final stage is called the dry down.
To be more specific, the scent of a perfume unfolds like this:
- Top notes -- This is what you smell when you first apply the perfume. It's the result of all of the scent ingredients blended together. This scent lasts only a few minutes.
- Middle notes -- As the most volatile of the scent molecules evaporate, the middle notes arise. This scent is considered the "heart" of the fragrance and lasts up to an hour.
- Base notes -- When the middle notes dissipate, the base notes take over. This is the dry-down period, and this final fragrance is said to reveal the "body" of the perfume -- its true scent. Fixatives are added to make the dry-down scent last for several hours.
Although a scent is designed by perfumers to unfold in a particular manner, it is not a uniform evolution. And this is where things get more interesting.