Fixative (perfumery)
A fixative is a substance used to equalize the vapor pressures, and thus the volatilities, of the raw materials in a perfume oil, and to increase the perfume's odour tenacity.
In simple words, fixatives increase the time for which the scent of a perfume lasts. They do this by slowing the rate at which the lighter scent molecules evaporate into the air.
Fixatives can be resinoids, terpenoids, or polycyclic ketones, which were originally obtained from animals, but are now mostly chemically synthesized because the artificial methods are more economical, more consistent and more ethical. Synthetic fixatives include substances of low volatility and virtually odorless solvents with very low vapor pressures.