Water in perfume: Why? What? How much?
The American Society of Perfumers once posted definitions of perfume extrait, eau de parfum (EDP), eau de toilette (EDT), and eau de cologne (EDC) on their website. Each was defined by the ratio of compound to alcohol. But beyond that, each was defined by what proof of alcohol was used, ranging from 200 proof — pure ethyl alcohol — down to about 170 proof — 85% alcohol diluted by 15% water.
It is no secret that as both the alcohol content and the water content go up, the price goes down. And, with the alcohol itself, as the water content goes up, the alcohol becomes cheaper.
This leads to the not untrue impression that the purpose of water in perfume is to reduce is manufacturing cost. Water is cheaper than alcohol and, unlike alcohol, is not government regulated and government taxed.
But there is more to water than its low cost. You begin to realize this when you notice that some quite costly fragrances include water, and fragrances which include water are far more trendy today than the increasingly rare and more costly "extraits" compounded from fragrance and alcohol alone.
Moreover, EDTs frequently come out ahead in reviewers preference to EDPs and pure perfumes. This suggest that while water may reduce the price, it also adds something pleasing to the fragrance. So what, I would ask, is the true role of water in perfume?
F.V. Wells (Bilot & Wells, Perfumery Technology) suggests ""The presence of water... generally increases the persistence of odours on the skin.""
Asking around, I received some additional insights into the value of water being added to the alcohol used in perfumery.
There was a general agreement that the addition of water lessens the harsh, drying effect of alcohol on the skin. So a less than 200 proof alcohol would make the perfume more pleasant when sprayed on the skin.
Other points were made. Agreeing with Wells, it was suggested that water would retard the evaporation of the alcohol, giving the top notes greater persistence (staying power), and perfumes are generally sold by the aroma of the top notes.
It was noted that a perfume with water would appear stronger to the nose as the water would help release the scent from the oil while pure alcohol would hold it back. This can lead to a balancing act by which less fragrance can produce the desired "smell strength" when alcohol of lower proof and higher water content is used, and this might explain why some find dollar store fragrances as acceptable or even nicer than their far more expensive originals.
Another point in favor of water is that in drying, alcohol can release "some boozy off-notes" from side products formed in traces. It was noted that even vodka produces smells beyond that of pure alcohol.
Finally, in a balancing act on which I am missing direct research, I was told that European and US formulations differed in compound strength because of differences in national diets, the US being a meat eating culture, requiring greater amounts of compound to achieve the same effect (or perhaps more water?) On this I was referred to the work of the late Paul Bedoukian who had written on the subject but have not been able to locate the original paper.
Summing up, water in the alcohol that is used to make perfume is not simply a "save money" ingredient. While there are different views on its overall role, there is general agreement that it works for the improvement of the user experience.
I personally suspect that a bit more is involved in the use of water in perfumery. Two points. Prior to the development of atomizers in the late 19th century, perfume was more viscous (less alcohol used) and more likely to be applied to articles of clothing or to fans or handkerchiefs than to skin. When applied to skin, it was dabbed on sparingly.
At the same time, toilet waters were on the market, lightly fragranced waters that required little or no alcohol as the flower essences were mostly soluble in water.
The atomizer brought about the need for lighter, more water-laden, fragrances that could be sprayed. Originally atomizers were sold separate from perfumes, to be self-filled by the consumer. But in the late 1930's, Coty for one developed locking, anti-leak atomizer bottles in which the fragrance itself could be sold.
So it seems to me that this technology brought about a merging of perfume and toilette water, the one gaining more water, the other gaining more alcohol. And this I would guess is how we have come to have water in our perfume today.
I have listed some vendors of de-ionized water here.
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