The world of aromatic essences is a rich and entangled one. On the one hand, the varied and intricate methods and products derived from natural materials. On the other, the many chemically-produced essences (nonetheless beautiful, sometimes) reproduced or even envisioned anew in the lab. Both worlds bring their own magic to perfumery, but wading the waters can become tricky. Here is a short but concise guide to making your way through the glossary of perfume terms referring to aroma extraction and essence production for use in perfumery.
The term "aroma extraction" refers to the extraction of aromatic compounds from raw materials, using methods such as distillation, solvent extraction, expression or enfleurage. Depending on the ratio of butter to aromatic compound, the etymology of the produced essences (essential oil, concrete, absolute, butter etc.) explains their properties. To a certain extent these procedures are damaging: they denature the aromatic compounds, either by changing their odor profile or sometimes by rendering them totally odorless! This has to do with the materials themselves, as often they have so little volatile oil that they do not yield a sufficient crop (lily of the valley and gardenia are good examples of this), or their chemical compounds are too delicate to withstand certain techniques (jasmine and tuberose had resisted for centuries, until the enfleurage technique—see below—was first used).
Botanical raw materials therefore aim on the whole at smelling as close as possible to the donor plant, something not always practically attainable. This is why many different methods have been devised to bypass the obstacles and to make way for better and more cost-effective technology.
Still, the perfumery raw materials thus produced serve a purpose in the fragrance industry and indeed a few have been some of the highlights in the rich and intricate history of perfumery itself.
Let's enumerate them, one by one.
EXPRESSION
Expression is among the oldest methods of fragrance extraction, producing an ESSENTIAL OIL from plants that are pressed, squeezed or compressed to yield an aromatic oil. Although King Tut's artifacts reveal lotus essences in alabaster vases, still retaining their aroma thousands of years later, these were first produced in unglazed ceramic vases, with the flowers pressed and then buried in the desert in the hopes of driving out water (which would seep through the porous material thanks to its relatively lower molecular weight, leaving behind the oily compound).
Today the only oils obtained by expression are those from the rind of citrus fruits, due to both the abundance of aromatics in the squeezable parts of the fruit (the rind) and due to the low cost of growing citrus fruits in general. Mechanically or cold-pressed, the peels of the hesperidia fruits are rich in oil and the extraction is thus cost-effective, rendering citrus essential oils among the cheapest of them all.
DISTILLATION
Distillation, using an alembic, is an advanced method developed in the Middle Ages, and a common technique for rendering a variety of perfumery aromatic essences, with the raw material sources comprising wood, bark, roots, flowers, leaves, seeds, peels and flowers. The resulting material is still mostly called an ESSENTIAL OIL, comprising aromatic and volatile active ingredients of the raw material, usually of plant form. Several very common essential oils such as peppermint, basil, lavender, rose, palmarosa, geranium or eucalyptus, are familiar to us from aromatherapy. Naturally the refinement of the process produces different quality grades of essential oils, making some finer than others.
Sandalwood oil is an essential oil obtained from the steam distillation of chips and billets cut from the heartwood of the Sandalwood tree. by ghknsg548
Another product that comes from steam distillation in particular is the HYDROSOL. The water boils and its steam is passed through the raw material directly for 60-100 minutes. The condensate from that distillation, containing both water and aromatic compounds, is settled in a Florentine flask. The fragrant oils separate on top of the distillate water, thus producing an ESSENTIAL OIL of the plant (the oily phase) and a HYDROSOL (the remaining water with some aromatic properties intact), the latter sometimes sold for consumer and commercial use (such as the popular rose hydrosols or orange blossom hydrosols) when it doesn't bear unpleasant by-products. Unfortunately there is no guarantee than a hydrosol will end up smelling nice. It's a trial and error process.
FRACTIONAL DISTILLATION
Fractional distillation (commonly used for Cananga odorata, aka ylang-ylang) means that a prolonged process is used, using a fractioning column, rendering several grades of the aromatic compound, accordingly varied in quality and depth of scent. This allows for greater control of the end material produced and is therefore very helpful to the perfum