Aromatherapy, believe it or not, is really benefiting from new, high-tech methods of essential oil distillation. These new methods are particularly suited to making fine essential oils of a few select varieties - though the 'tried and true' methods continue to produce excellent oils for the majority of aromatherapy uses. The newest technologies, involving low temperature extraction, are really adding possibilities, rather than replacing our favorite oils, in the aromatherapy enthusiast's toolkit. Here's a primer on modern essential oil distillation methods to help you make informed choices when shopping for your aromatherapy supplies.

A number of factors determine the final quality of a steam distilled essential oil. Aside from the plant material itself, most important are time, temperature and pressure, and the quality of the distillation equipment. Oils used in therapeutic aromatherapy are really very chemically-intricate liquids; each is made up of many, sometimes hundreds, of distinct molecules which come together to form the oil's aroma and therapeutic properties. Some of these molecules are fairly delicate structures which can be altered or destroyed by adverse environmental conditions. So, much like a fine meal is more flavorful when made with patience, most oils benefit from a long, slow 'cooking' process.

The temperature of the extraction chamber cannot be too high, lest some components of the oil be altered or destroyed. The same is true of the chamber's pressure. Lavender essential oil, for example, should not be processed at over 245 degrees F and three pounds per square inch of pressure (3 psi). Higher temperatures and/or pressures result in a 'harsh' aroma - more chemical than floral - and lessen the oil's therapeutic effects. Also, the extraction period must be allowed to continue for a certain period of time in order to flush ALL the oil's components from the plant, as some are released more quickly than others.

Despite the drawbacks of aggressive processing, high temperatures and pressures are often used to produces large quantities of oil in a short period of time. These oils are usually destined for use in cosmetic and processed food manufacturing, but are sometimes sold to final consumers as essential oils for use in aromatherapy. These oils will be less expensive, but are of limited therapeutic value, and the difference is apparent when the aromas are compared side-by-side. Some plants, and particularly flowers, do not lend themselves to steam distilling. They are too delicate, or their fragrance and therapeutic essences cannot be completely released by water alone. These oils will be produced as 'absolutes' - and while not technically considered essential oils they can still be of therapeutic value. Jasmine oil and Rose oil in particular are delicate flowers who's oils are often found in 'absolute' form.

The processing of an absolute first involves the hydrocarbon solvent extraction of a 'concrete' from the plant material, a semi-solid mixture of typically 50% wax and 50% volatile oil. The concrete is again processed using ethyl alcohol (the same alcohol found in beer, wine, etc.) in which the wax is only slightly soluble. The volatile plant oil separates into the alcohol and this mixture is removed. The alcohol is then evaporated and the result is an almost pure plant extract - depending on the care taken in the evaporation process, sometimes 2% or less of the ethyl alcohol may remain. The use of solvents in the extraction process notwithstanding, absolutes can have incredibly deep and complex aromas. The new high tech distillation methods include: Carbon Dioxide and Supercritical Carbon Dioxide extraction. Both methods involve the use of carbon dioxide as the 'solvent' which carries the essential oil away from the raw plant material. CO2 distillation uses carbon dioxide that is cooled and pressuried; the plant matter is bathed in this natural solvent much like it would be with steam distillation. The carbon dioxide in this condition is condensed to a liquid. Supercritical CO2 extraction (SCO2) involves carbon dioxide heated to 87 degrees F and pumped through the plant material at around 8,000 psi - under these conditions, the carbon dioxide is likened to a 'dense fog' or vapor. With release of the pressure in either process, the carbon dioxide escapes in its gaseous form, leaving the essential oil behind.

These carbon dioxide methods have a couple of advantages: Like steam distillation, there are no solvent residues left behind, and the resultant product is quite pure. Like solvent extraction, there is no heat applied to the plant material or essential oil to alter it in any way. The oil produced is very accurate with respect to the original state of the plant. The CO2 methods also are the most efficient, producing the most oil per amount of plant (one of the reasons for the high cost of essential oils is the low yield of oil from most plants - one ton of Rose petals produces less than 1 pound of oil, for example). The efficiency of CO2 extraction is particularly important when rare or endangered plant species are involved, such as Indian Sandalwood oil - less of the precious plant is needed to produce an equivalent amount of oil.