A Guide to the Extraction of Essential Oils
One of the main benefits of essential oils is the fact that they are natural substances. We love that in using these oils for healing, cleaning and aromatic benefits, that we are not putting even more toxic chemicals into our lungs.
But where do they come from? And how do we know they are all natural ingredients?
If you’ve researched essential oils at all, you’ve probably discovered that they are concentrated oils derived from aromatic plants. Currently there are over 600 plants that can be used for these products, and all of them are safe and natural for human and animal contact.
Several methods have been used throughout the centuries to get the final product. Some of them, such as steam distillation, are still used today, while others have become obsolete in recent years.
Methods of Extraction
· Steam Distillation
One of the oldest methods for essential oil extraction, steam distillation remains the most common for a couple of reasons. First, it has been found to be the most natural method in that it extracts the most oil without adding byproducts in the process. Secondly, it’s the most effective method for almost all plant matter.
For plants to be steam distilled, they are placed on a grid inside a metal still. The container is then sealed tightly and steam is injected in, usually through some sort of piping system through the bottom. The steam breaks up the plant material which causes it to release its oils. Once the still cools, the steam then returns to its liquid state, with the oils collecting on the surface in a collection vessel. Because water and oil don’t mix, the oils can easily be removed from the top.
Also sometimes called hydro-diffusion this method is a more recent discovery almost identical to the steam distillation process. This method also uses steam, but instead of the steam entering the vessel from the bottom, it comes in through the top. It’s also a faster method and is useful for extracting oils from woody materials or seeds like fennel.
The process with percolation is the same as steam distillation in that once the steam returns to its liquid state, the oils are skimmed off the top.
Expression, which is also commonly called cold pressing is the method used for extracting oils from most citrus materials, such as lemon and orange. Cold pressing has evolved over the centuries from manually soaking and pressing the fruit rind, to something known as ecuelle a piquer.
This process involves piercing, prodding and pressing the rind, which causes it to release its oil. While this can also be accomplished manually, today, there are machines manufactured for the task.
For this method, the peels are placed into a spiked container in which they are pressed and prodded. Once the oil is separated from the material, it is collected in a small area at the bottom. Some of the more modern machines also include centrifugal force to separate the oils from the rinds more quickly.
· Water Distillation
Water distillation is most commonly used with floral plants such as roses and orange blossoms. Using steam distillation for this delicate material will cause the petals to clump and wither, making it ineffective in removing the oils.
For this process, the botanicals are placed directly in the water, which acts as a type of barrier from the steam. The water is then brought to a boil which causes them to release their oils. The oil is then skimmed from the surface of the decanter just as it is with the other steam methods.
· Water and Steam
This method is the usually the method of choice for leafy plant material, such as herbs and certain florals. This process is similar to water distillation, except that the steam is applied outside of the container to gently and slowly heat the water to a boil. In this method, the plants are also placed in the water to protect them from overheating.
The oils are then collected the same way as with the water distillation, from an attached decanter where the oil rises to the surface and separates itself from the water.
Enfleurage is an ancient method rarely employed today that uses fat to absorb the oils from the plants.
To extract essential oils using enfleurage, the plant matter is placed and pressed into a thin layer of solidified animal or vegetable fat in a glass tray, where it remains for up to 2 weeks.
This process is repeated until the fat is completely saturated with the essence of the plants and the matter is then removed. The plants are then washed with alcohol, and the alcohol solution is stored in a container. Once the alcohol evaporates, the substance left in the containers is the pure essential oil of the plant. The remaining fat, or enfleurage pomade, can be used to make soaps and candles.
· Solvent Extraction
Solvent extraction is the least popular method due to the fact that it uses toxic substances such as hexane to extract the oils from the plants. In this method, the plants are punctured and placed in trays where they are washed repeatedly with the chemicals. The chemical wash will dissolve the plant material, leaving a waxy substance containing the plant’s oil, which is known as concrete. The concrete is then processed to be reduced to what is used as the essential oil.
The oil that is left from this method will retain trace amounts of the chemicals used to process it. While this makes it a less-desirable product, some plants such as jasmine are too delicate to endure the distillation process, making enfleurage one of the only options.
The basic methods of deriving essential oils from plants have evolved over the years, making it easier to obtain the product. When purchasing essential oils, it’s always best to find out which methods were used to extract the product. Extraction methods free from chemicals are always going to yield the most pure product which is what most aromatherapists recommend.