Perfumes are commonly used as a fashion accessory. They are used as a way of self expression and personality. Hence, is art used in formulating perfumes since perfumes are an expression of oneself? However, on the other hand, perfumes contain many weird chemicals. Then, with this, would it mean that perfumes are made through science?
Perfumery is the act of formulating perfumes (5). Basic ingredients in perfumes are fragrant chemicals and solvents. Scent of a perfume comes from the combination of fragrant chemicals like essential oils. These are volatile low molecular weight molecules which means it is easy for them to evaporate from their liquid to gas (3), the form for olfactory perception (10). On the other hand, solvents, like alcohol, are used as a medium to dilute and mix these essential oils together.
In perfumery, the attention is usually focused on the combination of essential oils for a perfect scent. Hence, it is important to understand that essential oils are divided into three “notes” - top, middle, and base - according to their ability to evaporate from liquid to gas. (4)
Top notes, also known as head notes (11), are the fastest ones to evaporate (4). They are smelled first for a few minutes after application, around 15 minutes (8). Top notes may smell fresh, citrusy, floral (delicate), etc. (2). Generally, a class of compounds called monoterpenes, which have a low molecular weight, falls under top notes. Being lightweight explains why top notes can evaporate faster. Some examples are natural monoterpene compounds like citronellol (6) in citronella (1) and geraniol (6) in geranium (1).
Middle notes are the main characters of the perfume. They are called the “heart” of the perfume (11). Middle notes are volatile compounds, but as they have a higher boiling point than the top notes, the middle notes evaporate later. For this reason, middle notes are more fixative than top notes and last longer up until the 3rd to 4th hour of application (8). They may smell sweet, woody, floral (heavy), etc. (2). Some sources are natural compounds like eugenol from basil and anisyl alcohol from aniseed (6), or heavier terpenes like sesquiterpenes and diterpenes. An example is a diterpene, sclareol, from sage (9).
Lastly, base notes are the slowest to evaporate. They are also volatile, just like top and middle notes. However, as base notes have a higher boiling point, they evaporate slower. Thus, the base notes are the last to be smelled. Their scent is released at the 5th to 8th hour after application (8). This makes the base notes the most fixative among all notes. Base notes are like supporting characters that help make the main characters shine more. They bring deepness to the scent of the perfume (8). Base notes can be sweet, woody, floral (heavy), etc. (2). Examples are vanillin of vanilla (6) and diterpenes (9) found in cypress (6).
The golden combination for perfumes is to have 15–25% of the top notes, 30–40% of middle notes, and 45–55% of base notes (7).
Understanding perfumery through science could give a better idea on how to formulate perfumes. Both scents and longevity can be maximized by understanding the chemical properties of the ingredients. However, trial and error is still performed as the determination of a scent to be wonderful still depends on creativity and preference. This is the art behind perfumery that science cannot give a formula to. With this, one can conclude that perfumery is both science and art.
References:
(1) Clarke, S. Families of compounds that occur in essential oils. Essential Chemistry for Aromatherapy 41-77 (2008). doi:10.1016/b978-0-443-10403-9.00003-0
(2) Heltovics, G., Holland, L., Mattila, J. & Warwick, J. Fragrance compositions. (2007).
(3) Khayyat, S. & Roselin, L. Recent progress in photochemical reaction on main components of some essential oils. Journal of Saudi Chemical Society 22, 855-875 (2018).
(4) Mata, V., Gomes, P. & Rodrigues, A. Perfumery ternary diagrams (PTD): a new concept applied to the optimization of perfume compositions. Flavour and Fragrance Journal 20, 465-471 (2005).
(5) Definition of Perfumery. Merriam-webster.com (2019). Retrieved November 10, 2019, from https://www.merriam-webster.com/dictionary/perfumery.
(6) Poucher, W. Perfumes, cosmetics and soaps. (Springer Science, 1993).
(7) Rodrigues, S. et al. Scentfashion®: Microencapsulated perfumes for textile application. Chemical Engineering Journal 149, 463-472 (2009).
(8) Sell, C. Chemistry of Fragrances. (Royal Society of Chemistry, 2006).
(9) Stewart, D. The chemistry of essential oils made simple.
(10) Teixeira, M., Rodríguez, O., Mata, V. & Rodrigues, A. The diffusion of perfume mixtures and the odor performance. Chemical Engineering Science 64, 2570-2589 (2009).
(11) What is the chemistry of a perfume?. worldofchemicals.com (2019). Retrieved November 10, 2019, from https://www.worldofchemicals.com/611/chemistry-articles/what-is-the-chemistry-of-a-perfume.html.