Before moving on to a series on what we usually think of as the perfume materials themselves, I thought it might be interesting to consider the component of most perfumes that everyone takes for granted, the carrier. Perfumes are generally fragrance materials diluted with a more or less odorless substance, never completely odorless, but benign enough to be masked and/or quick to evaporate.
By far the most common carrier is alcohol, usually 95% ethanol (ethyl alcohol), the same alcohol that’s in alcoholic beverages. Perfumer’s alcohol is typically grain alcohol that contains a bitter, low-odor “denaturant” that renders it unpalatable to drink, thus minimizing the chances that the alcohol could be resold as a beverage without the authorities having collected beverage taxes on it. If you see “SD alcohol” or “alcohol denat” on a perfume label, it just stands for “specially denatured alcohol”.
Some perfumers also use non-denatured alcohol, which can be obtained with the proper type of license. It is usually considerably more expensive than SD alcohol, and may be produced by craft distilleries that cater to the beverage and/or natural perfumery trade. Popular types of non-denatured alcohol include grain or potato alcohol, which have very little extra odor from the plant matter that was fermented and distilled, grape alcohol, which has a strong grappa smell, and sugar cane alcohol, which has a rum-like smell. These special effects are fine, if you want them in your perfume, but because of the extra expense and extra smells, most perfumers stick with the garden-variety SD alcohol.
Because alcohol is a non-polar solvent, it works well with most essential oils and aroma chemicals, which readily go into solution in alcohol and stay there. It is volatile, so evaporates quickly, leaving the less volatile fragrance materials behind for our enjoyment. Alcohol-based solutions are thin enough to easily be sprayed. The only down side is that ethanol is flammable at relatively low temperatures and has some smell of its own. Other than that, it’s the ideal carrier.
Oil is another traditional carrier for perfumes. Like alcohol, it easily mixes with essential oils and aroma chemicals. However, not every oil can work as a perfume base. Many oils have strong smells of their own (think about olive oil, or sesame oil). Unless the scent of the carrier oil is intended to be part of the fragrance, it is best to use low-odor oils. The other problem with oils is that many of them go rancid quickly. I will never forget pulling out some samples of oil-based perfumes that had been sitting around for about a year and being hit with the smell of rancid oil. It was so bad that I had to throw them away. The oils that I’ve used that tend not to go rancid are argan and fractionated coconut oil (FCO). Grapefruit seed oil can be added as a natural preservative and, of course, there are lots of synthetic preservatives that will work with oil.
Traditional attars are made from flowers or other materials distilled into a carrier of sandalwood oil or vetiver oil, both of which have their own scent that contributes to the attar. Today some attars are distilled into diethylphthalate (DEP) or dioctylphthalate (DOP), which act as cheap substitutes for the traditional oils. If you are buying attars and want to avoid phthalates, you should find out what the carrier is. Oil-based perfumes tend to go on sticky, with the fragrance developing more slowly than it does in alcohol-based ones.
I have tried a few water-based perfumes and was not impressed. First, most fragrance materials are not soluble in water, so the best that can be done is to produce a suspension or emulsion of the oils or aroma chemicals. For this reason, water-based perfumes tend to be cloudy. The amount of fragrance that can be added to water is limited, so they are usually quite weak.
Concentrations of fragrance materials in carrier are all over the place, ranging from minute amounts of fragrance materials to the pure concentrate. The highest concentrations are found in attars and concentrated perfume oils (CPOs), followed (in theory) by extraits/parfum, eau de parfum (EdP), eau de toilette (EdT), eau de cologne (EdC), and body sprays, which typically use a carrier with a high ratio of water to alcohol. However, you can’t really go by these designations because an EdT may smell stronger than an extrait. It depends on the fragrance itself and how the manufacturer defines the terms.
[Except for (maybe) the 190 proof grain alcohol in the first photo, all are things that should not be in perfume, just included for the visual interest. All images are from Wikimedia]