It’s fascinating to look at how essential oils are distilled. The majority are steam distilled but there are some which are distilled or extracted in other ways.
Essential oils need to be extracted in specific ways for specific oils. Here is a list, with a short description of each.
The most common method of extracting an essential oil from the plant is through steam distillation. Low temperature and low pressure play an important part of collecting the highest quality essential oil. When plant matter is placed into a chamber and steam is injected, the plant’s essential oil is released into the air. The steam and essential oil are carried out of the chamber and cooled. The oil and water are then allowed to separate for collection. Using a higher temperature and greater pressure will allow a larger amount of oil to be released from the plant. The scent will remain intact, and possibly stronger, but the quality of the oil will suffer greatly. Oils distilled at higher temperature and pressure for the fragrance will not perform like therapeutic quality oils distilled at low pressure and low temperature.
The water collected after the distillation is often sold as a hydrosol.
Oils: Just about everything, other than those listed under the other methods.
With hydro distillation the plant is distilled using water rather than steam. The plant matter is placed in a chamber filled with water, which is then heated until the oil is released. This extraction process produces a superior quality essential oil, but it also is quite a bit more labor intensive.
Oils: Birch Bark, Frankincense, Balsam of Peru, Copaiba Balsam, Galbanum, Vetiver
This method uses a solvent or chemical to extract the oil, usually hexane. Once the oil is extracted, the chemical is then removed from the oil. An oil that is extracted as an absolute will always have some of the chemical remaining. A high quality absolute will have less than 1% of solvent remaining.
Some plants, like Jasmine for example, will only give up their oil using this extraction process. Therefore there is no such thing as Jasmine essential oil but there is Jasmine absolute.
Roses can be either steam distilled or absolute distilled. The steam distilled Roses are the superior quality, though it is a much higher price due to the immense volume of rose petals needed. Rose absolute, or Rose otto as it is usually known, is not as expensive, nor is it as intense a scent as distilled Rose.
Oils: Jasmine, Rose Otto, Vanilla
Cold pressed is a method where the essential oil is pressed from the plant. This is the most common method of extraction for the citrus oils. The peel of the citrus plant is pressed and the essential oil is then filtered from the plant matter. While this method uses no heat and therefore produces a high quality essential oil, there are a few drawbacks to this extraction method. Within the pressed citrus oils there are microscopic amounts of peel and waxes. These parts of the plant will begin to break down and provide a shorter shelf life than other distilled oils. On average you can expect a shelf life of 6 months to 1 year from pressed oils while the other extraction methods will extend the shelf life for many years, if stored properly.
Oils: Bergamot, Orange, Lemon, Lime, Tangerine, Pink and White Grapefruit, Red Mandarin, Black Cumin, Cucumber Seed. Bergamot FCF is cold pressed and then steam distilled afterwards to remove the furocoumarins so it is safe to wear out in the sun.
The equipment for this type of extraction is pretty expensive and huge. It’s a fairly complicated process but how it works, in essence, is the carbon dioxide gas is employed at extremely high pressure to dissolve the oils from the plant material. Once the pressure falls, the oils form a mist which is then collected. The oils are free from extra residues when extracted this way. Due to the expense of the equipment and how long it takes for the distiller to recoup the money spent on it, oils produced through CO2 extraction are fairly expensive. But they are worth it.
Oils: Myrrh, Angelica Root, Galbanum
- The Illustrated Encyclopedia of Essential Oils: The Complete Guide to the Use of Oils in Aromatherapy & Herbalism by Julia Lawless
- The Encyclopedia of Aromatherapy by Chrissie Wildwood
- The Art of Aromatherapy: The Healing and Beautifying Properties of the Essential Oils of Flowers and Herbs by Robert B. Tisserand