The sense of smell, or olfaction, varies dramatically from one person to the next [source: Monell Chemical Senses Center]. What we can and cannot smell is often genetic, scientists are finding [source: Howgego]. Some people are simply born with the ability to smell more substances, and with greater sensitivity, than others.
Perfumers are some of those people. A "good nose" is critical to the work, as is curiosity [source: Academic Invest]. Great perfumers are constantly experimenting, combining essential oils in surprising ways as they search for some elusive aroma, an olfactory experience that achieves the desired emotion or effect when someone applies it.
That's the art. The science is molecular chemistry, the critical platform on which this creative experimenting and innovating rests.
Scents are particles of matter, comprised of molecules. When those molecules attach to any of the scent receptors in the human nose, the brain interprets them as smells [source: Stone]. The chemical properties of scent molecules determine not only how they smell but also how they act and interact, evident in the behavior of a perfume's three scent components: top notes, middle notes and base notes [source: Perfume.org]:
- The top notes are quickest to the nose and quickest to dissipate, because their molecules are small and volatile.
- The middle notes reach the nose second and last long enough to overlap with the third component, the base notes.
- The base notes last the longest and create the overall sense of a perfume. (See How Perfume Works to learn more about notes).
Perfumers use their knowledge of these molecular properties to design a scent that "unfolds," or evolves over time. And when they set out to create a scent, they start at the bottom, with the base notes.