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One of the confusing aspects about aromatherapy is that of cohobation.
Cohobation is a redistillation of a liquid by pouring it back repeatedly on the same matter from which it was initially distilled.
v. t. 1. (Anc. Chem.) To repeat the distillation of, pouring the liquor back upon the matter remaining in the vessel.
[imp. & p. p. Cohobated; p. pr. & vb. n. Cohobating.]
For preparation of medicines Count Mattei relied upon the Cohobation process of Paracelsus by which Spagiric tinctures of all the plants are extracted.
This process is also known as cold fermentation process.
Many alchemists throughout history have held the curious belief that for a process to be successful it must be repeated many times. So it was common for substances not only to be distilled, but for the products of distillation to be returned to their residue and distilled again, perhaps several hundred times. This was so common a technique that a special piece of apparatus was designed to make the whole process automatic, a flask with return tubes from the neck for the vapour to condense and pass back into the base of the vessel. It was called a blind alembic or a pelican. The latter name derives from the medieval heraldic image representing the ancient legend of the long-necked pelican wounding its breast to feed its young on its blood, the curve of the bird's neck resembling one of the curved return tubes on the flask. The origins of the word cohobation are mysterious, though the OED surmises that it may derive from an Arabic dialect root for "repeat".
When rose oil is extracted during water distillation, the one main constituent - phenyl ethyl alcohol - dissolves into the water of the distillation still and does not form part of the essential oil that is so extracted.
The oil so extracted is therefore not whole, and is deficient in this rose-smelling ingredient - and in order to produce a "complete" oil, the phenyl ethyl alcohol needs to be distilled from the water in which it dissolved and added back to the "incomplete oil". When this phenyl ethyl alcohol is so distilled, it is added back to the original distillate, in the correct proportion, to form a complete and whole rose oil, and is then called Rose Otto.
We have no such documentation on the origins of cohobation, the technique that is the key to maximizing the yield of attar. There are no certain reports of its use by the early Muslim alchemists, no mention in literature, and no description of it in any travel account earlier than the second half of the 16th century. We have only one clue, from etymology, that the technique may be of Arab origin. The word kohob was used by Paracelsus to mean "repetition," and that word may derive from Arabic ka'aba, "to repeat [an action]."
Michael R. Hayward, a dental surgeon who works in Saudi Arabia, has a special interest in perfumes. He lives in Dhahran. He expresses a belief is that cohobation was developed independently in Europe, India and the Arab world, probably-in the case of Europe-in the mid-16th century:
A European source dated 1574 names Geronimo Rossi of Ravenna as the first to accomplish cohobation, and oleum rosarum distillatum-distilled oil of roses-appears in German apothecaries' price lists of the 1580's.
There is also a theory that places the invention in Bulgaria, an important rose-growing country for the past 350 or 400 years. Its adherents point out that multiple distillation was already a well-understood technology in Bulgaria by the time the Ottomans brought the oil-bearing rose there in the first half of the 17th century. To the north of what is now known as the Rose Valley, in the villages around the towns of Gabrovo, Sevlievo and Troyan, plum brandy had been produced for years, its strength and quality increased by repeated distillation. The Ottomans discouraged the production of alcohol, but the distilleries, and the technique of cohobation, were easily adapted to the production of attar of roses.
In my opinion, the world's most beautiful attars today come from Bulgaria, Saudi Arabia and Russia, each with a subtle yet distinctive nuance: of spice, honey and softer-hued tonalities respectively. To the many successive generations of inventors who made the production of such beauty possible, we owe our thanks.
Marcia Elston http://www.wingedseed.com