As to the manufacture of essential oils, there are at least five common methods that may be employed to obtain the final product. These are enfleurage, maceration, evaporation, expression, and distillation. Although there are some peculiar variations of these, in general these are the basic ways in which to extract essential oils from nature.
Enfleurage
Enfleurage has been in use since ancient times. One of the attractions of this method is the romanticism of revisiting the ways of the past, and also that it requires no fancy equipment and is suitable for the home production of fragrant oils. The raw flowers or herbs are soaked in a host or carrier oil, and the essence is absorbed by the liquid. After a couple of days, the plant matter is removed and replaced by fresh material. This process is repeated until the remaining oil is of the scent potency desired.
Originally, animal fat may have been used in the process of enfleurage. However, for use in aromatherapy, many disdain the use of animal byproducts. The oil that is now normally used for extraction is one with little scent of its own. Some good candidates are sesame, sunflower, calendula, or almond (unlike the common synthetics that are designed to capture the fragrance of the plant, true almond oil actually has very little scent).
Maceration
Maceration is a method similar to enfleurage and may be nearly as dated in its employment. The major difference between the two systems is that, in maceration, the plant material is crushed before being immersed in oil to extract its essence. As in the prior method, after a few days, the herb or flower is strained out of the solution and replaced with freshly crushed leaves or blossoms. This process is repeated until the desired scent potency is reached.
One method of speeding the process of extraction is the introduction of heat. A popular way to accomplish this is to leave the vessel of soaking herbs in the sun, similar to the brewing of sun tea. Culpeper suggests that an appropriate cooking time is about a fortnight, or two weeks, depending on the season and directness of the sun’s rays.
Evaporation
A third method of manufacturing essential oil products is through evaporation. In this method, solvents are employed for the extraction of the fragrant essence. This is a multi-step process. The plant is sealed up in a container with a solvent such as benzene. The essence is drawn into the solvent. The accomplishment of this first procedure is easily recognized by the strong aroma adopted by the solvent. Often, the plant material will also become limp and faded. Its color is often drawn out along with its fragrance. After this step is complete, the solvent solution is heated. One of the characteristics of solvents is that they have a low boiling point. As the solvent boils away, the plant essence that was drawn into it remains. This can be added to a low-scent oil to make a usable essential oil or it may be mixed with alcohol to make a tincture of the essence.
Expression
Expression is employed primarily in commercial development of essentia! oils. This is accomplished through cold pressing the plant materials in order to squeeze out the essence from the host. Because a great deai of pressure is required to arrive at the end product, this is a method that is best left to the factories, with their advanced and often costly machinery. A hand press cannot arrive at the same quality product that is possible through commercial development.
Distillation
Another ancient system for manufacturing essential oils is distillation. While this does require some equipment, it is not unlike the homemade stills that have speckled the hill country for generations, producing moonshine. The plants or flowers are either boiled or steamed in a closed cooker that culminates in a thin tube. As the pressure in the unit heightens, the extracted oil will rise to the top of the boiling water. It is then forced through the tube and collected by a waiting container as it drips out.