Sillage in perfume refers to the aura or trail created by a perfume when it is worn on the skin. It comes from the word in French for "wake" and can best be described as how a fragrance diffuses around the wearer. Sillage or diffusion in fragrances can also be called the "projection" of a fragrance. Compounds such as Hedione can be used to enhance the diffusivity of a fragrance. Hedione is a syntheticrelative of methyl jasmonate, a naturally occurring compound in floral scents such as jasmine, tuberose and magnolia. Methyl jasmonate is also found in many other plant parts and is considered to be a signalling molecule. It is considered one of the compounds responsible for the projection of the scent in living flowers and was first fully characterised between 1957 and 1962 in jasmine absolute by the fragrance chemist Edouard Demole who was working at Firmenich. The first commercially successful fragrance to utilise Hedione was Eau Sauvage by perfumer Edmond Roudnitska for Christian Dior, launched in 1966. The addition of Hedione to a classically hesperidic fragrance construction created a dewy lemony magnolia-jasmine dimension without being directly floral, and gave it a new type of projection and transparency not experienced before in this type of perfume. This is considered to be the beginning of a new trend in perfumery towards transparency and projection. Compounds such as damascones, Iso-E super, linalool and some of the synthetic musks such as cashmeran may also be added to fragrances to enhance their diffusion and sillage. A fragrance does not need to be a heavy one to have a large sillage; fragrances such as Giorgio Beverly Hills for women and Poison are very good examples of this. Eau Sauvage and L'eau d'Issey have a large sillage but may be considered much lighter examples of this. Sillage in a perfume could also be considered to be how a fragrance is perceived by others around the wearer and is enhanced by motion, ambient temperature as well as the inherent qualities of the skin. According to an article by Mookerjee, a fragrance is perceived by the diffusion of individual fragrance molecules. The rate of diffusion of these molecules in a fragrance, however, appears to be independent of their molecular weights, boiling points, odour thresholds and odour value. Once a fragrance is applied to the skin, the skin itself becomes a substrate to the scent. The inherent scent of the individual skin, moisturisation of the skin, the behaviour of the microbiome of the skin, and the temperature of the surface of the skin that the fragrance is applied to will affect the sillage or diffusion of a perfume applied to it.
