Sillage, or projection, is a French term that is commonly used to discuss a fragrance’s diffuseness, an ability of a scent to be smelled at a distance; the bigger the distance, the stronger sillage is. Longevity, on the other hand, refers to how long a fragrance lasts once applied. And the two don’t necessarily correlate – sometimes we encounter fragrances with huge sillage but short longevity, and vice versa.
But those interested in fragrance regularly ask the question, “Which fragrances have the best longevity and sillage?” Many of us value a fragrance that is readily perceivable and that will last for hours after application; and others of us don’t feel that it is such an important quality – the actual aroma, or the fragrance identity is what we are most concerned about.
Sillage and longevity are sometimes wrongly connected to a perfume’s concentration with eau de cologne having the weakest sillage and longevity and perfume extrait to be the most powerful and longest lasting. They might be connected, but they are not at all in a direct correlation. For example, we’ve often encountered colognes that are powerful and extrait that are quiet.
Talking about individual raw materials, sillage is just a physical property like boiling point or color, and it is sometimes really hard to predict. What causes sillage? Technically speaking, the lower the odour threshold of the substance and the higher its volatility, the bigger the sillage will be. It is not at all easy to predict the general sillage of a fragrant mixture as sometimes, and in certain conditions, even very diffusive materials can lose their penetrating power, and vice versa. Sillage or diffuseness is a very important property of modern fragrances. Along with perfume identity, longevity and sillage encompass the 3 pillars of contemporary perfumery.