I’m not sure that everyone who enjoys perfume is clear about
the difference between an essential oil and an absolute, partly because the
distinction often gets lost in the listing of notes, the hype, and the fact
that there are vendors who sell “essential oils” purported to be from materials
that do not lend themselves to the distillation of oils. If the price you see
for “frangipani absolute” is absurdly cheap, what you would be buying is
neither an essential oil nor an absolute. Re-sellers may not even be aware of
this issue, perpetuating it among the users of materials for perfume and
aromatherapy. There’s nothing wrong with a synthetic fragrance oil meant to
smell like frangipani, in fact, it might smell more realistic than the natural
extractions, but if that’s what it is, it should be labeled as such.
Essential oils are steam-distilled or cold-pressed. Any
material that contains a lot of oil, like citrus peels, can be cold-pressed.
You’ve probably done this accidentally while peeling an orange and getting the oil
on your hands. You could even do cold-pressing at home as a demonstration or
experiment if you have enough citrus peels and a separatory funnel to remove
the water-based layer or are willing to skim the oil off the top. For materials
that contain a smaller ratio of oil to other materials, steam distillation heats
the plant material, and the distillate is condensed and collected. Generally
the oils are more volatile than the water, but both will come out of the
condenser during the course of distillation. In this method, too, there is an
oil layer and an aqueous layer, which must be separated. The aqueous layer is
sometimes sold as a “hydrosol”. It generally contains a small quantity of
aromatic molecules, so can be used in various cosmetic applications.
As I mentioned in my last Wednesday post, some materials do
not lend themselves to steam distillation. These include many types of flowers.
Other materials, like lavender, can be steam-distilled to produce an essential
oil or extracted to produce an absolute. Generally, the essential oil will
smell different from the absolute because a different subset of molecules is
extracted by each method. In many cases the absolute (or other type of extract)
will smell more like the natural material. The choice of which to use in
perfumery depends on the desired scent properties, price, availability, and so
on. Absolutes are almost always more expensive than essential oils, assuming
both are available, but the extra expense may be worth it if the material is
featured in the composition and a naturalistic scent is desired. And sometimes
a synthetic reconstruction does the trick.
[Top and bottom photos are3 mine, orange peel photo from a commercial website]
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