Oils and scent

The teaching

As the craft of the distiller and the perfumer teaches it.

What an essential oil is

An essential oil is the scented, volatile part of a plant: the small molecules that rise from it into the air and that the nose meets as its smell. It is called an oil though it is not fatty, because like oil it will not mix with water. It is concentrated far beyond the plant: several tonnes of rose petals make a single kilogram of rose oil. A drop is therefore not a little of the plant but a great deal of it, and that is the root of every caution about it.

How oils are drawn

Most oils are distilled. Steam is passed through the leaves, flowers, wood or seeds and carries the scent away; it is cooled, and the oil floats off the water, which keeps a little of the scent and is sold as a flower water, rose water or orange-flower water. The peels of citrus fruit are pressed cold instead.

Flowers too delicate for steam, jasmine and tuberose above all, were once laid on trays of fat, renewed daily for weeks until the fat was saturated with their scent, a slow craft called enfleurage. Today they are steeped in a solvent, which gives a waxy concrete and then, washed with alcohol, an absolute. Carbon dioxide under pressure is the newest solvent of all.

Notes, as perfumers teach

Perfumers sort scents by how quickly they fade. The top notes, citrus and fresh herbs, are met first and are gone within minutes or an hour. The heart notes, the flowers and the spices, unfold over hours. The base notes, woods, resins, mosses and musks, last a day or more and hold the rest in place, for which they are called fixatives. The perfumer Septimus Piesse set odours on a musical scale, matching each to a note, and the musical language has stayed with the craft: a blend has its notes, its chords and its harmony.

The families of scent

Perfumers also group scents into families: citrus, bright and fleeting; floral, the rose, jasmine and orange blossom; herbal and green, lavender, rosemary and the cut leaf; spicy, cinnamon, clove and pepper; woody, sandalwood, cedar and vetiver; resinous and balsamic, frankincense, myrrh, benzoin and labdanum; and earthy, patchouli and the roots. Learning a family teaches the nose to tell its members apart.

What the scents have stood for

Rose is the flower of Venus and of love, and in Christian devotion of the Virgin Mary; in Persian poetry the nightingale sings its longing to the rose. Lavender, whose name is often taken from the Latin for washing, stands for cleanliness and calm, and was laid among linen. Rosemary is for remembrance, as Ophelia says, 'There's rosemary, that's for remembrance', and was carried at weddings and at funerals alike. Jasmine, which opens and smells strongest at night, is woven into garlands for worship and for brides in India.

Orange blossom crowned brides in Europe as a sign of purity and fruitfulness, and its oil, neroli, is named after a princess of Nerola who loved it. Sandalwood is the scent of the temple, cedar of things that do not decay, and vetiver of cool earth, for its roots were woven into screens in India and wetted against the heat. Patchouli was once packed with Indian shawls to keep the moths away, until its smell became the sign of the real thing.

The aromatherapy books

Aromatherapy, as its books teach it, gives each oil a character and a use: lavender calms and balances; peppermint cools and wakes; rosemary clears the head and helps the memory; eucalyptus opens the breath; chamomile soothes; bergamot lifts the spirits; ylang-ylang is sensual and euphoric; sandalwood and frankincense quieten the mind and slow the breath. Its teachers blend oils for the person and not only for the complaint, which Marguerite Maury called the individual prescription. The house takes from this teaching its language of scent and mood, and uses the oils by smell alone.

Learning to smell

The perfumer's way of smelling is both the safest and the most instructive. Dip the tip of a strip of plain paper in the oil, or touch a single drop to it, wave it once, and hold it a little below the nose; never sniff from the bottle. Smell it again after ten minutes, after an hour and the next morning, and write down what has changed, for the top notes leave and the heart appears. Rest between scents, and smell no more than a few at a sitting, because the nose tires quickly.

Why oils can harm

Because they are so concentrated, essential oils are not gentle. Put neat on the skin, many burn or redden it, and some, cinnamon bark and clove among them, can cause an allergy that lasts for life; old, oxidised oils are worse. Citrus oils pressed from the peel, bergamot, lime and lemon above all, can make skin blister in sunlight. Swallowed, oils poison, camphor, clove and pennyroyal among them, and the victims are often children. That is why the house uses them by scent alone, and why nothing here is a reason to put an oil on the skin or in the mouth.

Children, animals and others at risk

Some people and creatures need special care. Peppermint and eucalyptus held near a baby's face can make its breathing falter. Cats cannot break down many oils, citrus, peppermint, eucalyptus, pine and wintergreen among them, and should never be shut in a room with a diffuser; birds, with their delicate lungs, are kept away from scented vapour altogether, and dogs too can be poisoned. Many oils are advised against in pregnancy; some, rosemary and sage among them, can bring on seizures in people with epilepsy; and diffused oils can set off asthma. The label, a doctor and a vet come first.

Keeping oils

Oils are kept tightly closed in dark glass, somewhere cool and away from flame, for they catch fire readily. Light and air change them as they age, and an old oil smells flat or sharp and irritates more; citrus oils keep the shortest time. A good bottle names the plant by its Latin name, the part used, the country and the method, since cheaper oils and synthetics are often sold under dearer names, as lavandin is sold as lavender. A fragrance oil is a made perfume, not an essential oil at all.