Essential oils are aromatic, non-greasy plant extracts composed only of the volatile molecules from the plants concerned.

The word ‘volatile’ is from the Latin word ‘volaire’ which means to fly away. All aromatic substances are volatile and their volatility is determined by their molecular structure.

In perfumery, aromas are divided into three separate groups – top, middle and base notes.

Volatility is determined by how long the perfume will exist in the atmosphere.

Test for volatility:

If a number of drops of an essential oil containing all top notes were put on a tissue this would evaporate completely, leaving no mark or smell within a number of hours.

If a number of drops of an essential oil containing all middle notes were put on a tissue this could take 2 to 3 days to evaporate completely, leaving no mark or smell.

If a number of drops of an essential oil containing all base notes were put on a tissue this could take up to 5 days to evaporate completely, leaving no mark or smell.

 In aromatherapy this information is not needed to select a “healing blend” for our clients. It does however have an effect on the “lasting power” of any blend we choose to make and should be considered when selecting oils to use in a vaporiser or perfume blend.

It is important to note that top, middle and base notes do NOT determine the length of time essential oils stay in the body. This is determined by the individual and their metabolic rate.

Discussing essential oils as top middle and base notes would lead a person to think that essential oils were composed of either top, middle or base notes. This is most definitely not the case. An essential oil is a complex cocktail of chemicals and each individual essential oil contains different proportions of molecules of different sizes. A ‘top note’ essential oil will have a predominance of smaller, more volatile molecules, whilst a ‘base note’ essential oil will have a predominance of larger, heavier molecules. A ‘middle note’ essential oil contains a blend of different sized molecules in more or less equal proportions.

It should be observed that the actual difference in the size of these molecules is minute.