Understanding how a fragrance performs requires looking beyond whether a scent is simply "strong." In perfumery, performance is measured across three distinct parameters: sillage, projection, and longevity.
1. Projection: The Fragrance Bubble (Static Distance)
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What It Means: Projection measures how far a scent radiates outward from your body while standing in place.
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The Concept: Think of projection as your personal scent bubble. It determines the physical distance at which someone near you can detect the fragrance without directly leaning in.
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Key Factors: Projection is driven primarily by volatility and alcohol content. Formulations with higher alcohol percentages (like Eau de Toilette) evaporate quickly, launching top-note molecules into the surrounding air for an expansive opening radius.
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Scale of Measurement:
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Intimate (Skin Scent): Detected only within 1–2 inches of the skin.
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Moderate (Arms-Length): Noticeable within a standard conversational distance (1–3 feet).
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Enormous (Beast Mode): Radiates across a room (6+ feet).
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2. Sillage: The Scent Trail (Kinetic Wake)
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What It Means: Derived from the French word for "wake" (like the path left behind a boat in water), sillage (pronounced see-yahzh) describes the aromatic vapor trail left hanging in the air after you walk past or leave a room.
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The Concept: A fragrance can have moderate projection while you sit still, but produce a lingering, mesmerizing sillage trail when you move.
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Key Factors: Sillage depends on molecular weight and how long heavier scent particles (like musks, ambers, resins, and synthetic fixatives like Hedione or Iso E Super) hang suspended in the air before dissipating.
3. Longevity: The Lifespan on Skin (Time)
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What It Means: Longevity refers exclusively to duration: how many hours a fragrance remains detectable on your skin or clothing from initial spray to final drydown.
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The Concept: Longevity is purely a function of time, measured until the base notes completely vanish.
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Key Factors: Dictated by oil concentration (Extrait de Parfum vs. Eau de Cologne), the natural evaporation rate of raw materials (citrus burns off in minutes, while oud and patchouli anchor for hours), and individual skin chemistry/hydration levels.
The Olfactory Fatigue Trap (Nose Blindness / Anosmia): If you stop smelling your perfume after 30 minutes, it does not mean its longevity, sillage, or projection has ended. The brain’s olfactory receptors naturally filter out continuous ambient scents to remain alert to new environmental odors.