By the ninth century the Arabs had discovered how to distil rose water. A physician called Salernus, who lived in Salerno in the eleventh century, records the process of distillation in his book Antidotarium Magnum, while Albert le Grand (1193-1280)，a man of the church and a philosopher, wrote recipes for the distillation of alcohol in his book De Secretis Mulierum: one was for L ’Eau Ardente, and was highly flammable; another was for Eau de Vie; and there were recipes for Esprit de Vin and Eau Flagrante. These fiery waters and volatile liquids replaced some of the oils in perfumes. The art of perfume distillation, however, was not perfected until the seventeenth century.
By the early fourteenth century most perfumes were a combination of alcohol and essential oils. For instance, rosemary and Eau de Vie were distilled in a bain-marie, an invention of a hermit who made one especially for Queen Elizabeth of Hungary in about 1370. In sixteenth-century Tuscany, distillation was the preoccupation of all scientists. The quality of the essences improved when the process of heating the perfume was slowed down. Essences were put into an alembic, which was placed in a bain-marie with a mirror of steel beside the alembic to capture the sun’s heat and so warm the essence gently.
Towards the end of the sixteenth century two further important discoveries were made: how to siphon off the scented water and how to preserve the droplets of oil to make the essence. The Florentines invented the Florentine vase, which was serpentine and had two apertures，one for oil and one for water. At the same time a kind of enfleurage was discovered, in which orange flowers, jasmine, rose and violet leaves were immersed in layers of almond oil so that the odour of the flowers was absorbed by the oil. And Leonardo da Vinci invented the process of maceration – softening the ingredient by steeping it in a liquid – and then used solvents to extract essences.
These days raw ingredients, such as rose heads, oak moss or momosa stamens, are distilled in vats, where they are boiled with water or a solvent so that the essential oils are released as a vapour with the steam. The scented steam then passes up and along a pipe, where it cools back down into a mixture of water and essential oil, which, in turn, drips down into a vat. As most oils float on the surface of water, they can then easily be siphoned off. Most flowers have to be distilled when they are fresh, just after they have been picked.
With natural components, the top notes often disturb the terpenes (volatile aromatic hydrocarbons which occur naturally in essential oils), so, to obtain a cleaner odour, the terpenes have to be taken out. In an essential oil there are hundreds of natural components and sometimes some of those disturb the dominant odour, so, to produce a finer product，a second distillation is required. This is called molecular distillation.
Products are often de-coloured, too, because these days people prefer colourless and transparent perfumes. An absolute of rose,for example, which is naturally dark orange, can be made transparent. Each time a product is altered, all the machinery, every boiler, valve and pipe, has to be steamed to prevent ‘odour pollution’ which, once it has set in, cannot be removed.
Extraction is done by using solvents – like hexane, for example, which is an odourless by-product of petrol – which are often volatile. During this process a wax, or ‘concrete’, which is a solid viscous substance, is obtained. The wax is treated several times, either with a solvent or with alcohol. The solvent or alcohol dillutes the wax and then, when the solvent or alcohol is eliminated – using a repeated vacuum process in the case of solvents – the wax, or concrete, becomes more and more concentrated. When the wax is separated from the perfume using the alcohol process, the perfume is translated into an ‘absolute’，which – unlike an essential oil, which is distilled – is obtained by the extraction process and is an altogether more potent and purer product. The perfumers then work with the essential oil, or with the concrete, or with the absolute. Perfumes created using the wax and alcohol process are usually 10-20 per cent concentrate and 80-90 per cent alcohol.
For some plants, extraction doesn’t result in anything interesting whereas distillation does, but the reverse is also true. Different components result from the two processes. For instance, the Rose de Mai from Grasse is not distilled = the yield would be too small and the price would be too high. But the Bulgarian rose can be extracted into a concrete and then into an absolute; it can also be distilled into an essential oil.
And it is as well to remember that extraction units can be dangerous places. The solvents are so flammable and so volatile that a telephone or a tape recorder can cause an explosion. A journalist once caused a blast with his camera flash in Laboratoire Monique Remy. Distillation units, on the other hand, use water and so are far less hazardous.