Any answer to the question “What makes a fragrance substantive?" faces a limitation based on the fact that substantivity of perfumes can only be deflned in an operational sense. The perfumer calls a fragrance or an odorant substance substantive in a perfumed product if the odor is perceptible throughout the stages of the product’s application cycle. For example, in a fabric softener a substantive odorant substance would be perceptible in the detergent itself, in the wet laundry after washing, and in the dried laundry, among other stages in the product’s application cycle.
The application chemist’s point of view is similar. However, in attempting to get a quantitative determination of the odorant’s time-dependent concentration in the headspace above the perfumed product, the modern application chemist links the headspace concentration to the odor perceived, either by calcuIating the number of odor value units (OV units) present in the headspace, or by taking into consideration the slope of the dose-effect curves of the perfume’s components. It is important to note that these determinations are usually made “in praxi” for a state of equilibrium and that the storage conditions between measurements reflect the practical situation and do not necessarily represent equilibrium states.
In this article, the substantivity of fragrance is discussed as a function of the vapor pressures, perception threshold values, odor values, water solubilities and matrix factors of ten fragrance raw materials investigated mainly in view on their application in fabric softeners.