The molecules of each ingredient in a fragrance evaporate from the skin at different speeds, according to their size and volatility - all the while interacting both with the fragrance's other ingredients and with the wearer's skin chemistry. In perfumes like Ffern's that use natural ingredients, ingredients may contain many hundreds of different molecules, all of which contribute to the overall scent profile of a fragrance.
Associated with the dry-down period, base notes are the cellos, bassoons and double basses of a fragrance, the foundation upon which it is built. Last to evaporate, they underscore playful, fading top notes and blend intricately with richer mid notes, leaving a lasting impression. They are often woody or earthy and include excellent fixatives such as oakmoss, which binds onto more volatile notes to decrease their reactivity and thus lengthen their evaporation time.