These botanicals usually have a pleasant fragrance as well. The oils must be extracted for these properties to be used. There are several methods of extraction.
Steam Distillation
Steam distillation is the most common method used to extract essential oils from the flowers, leaves, stems, bark, grass and seeds of botanicals. Many distillers believe that this method is the only way to produce oils of the best quality.
Steam distillation is done by placing fresh, or sometimes dried, plant materials into a plant chamber on a still. Pressurized steam is produced in a separate chamber and circulated through the chamber containing the plant material. The steam’s heat forces the intercellular pockets within the plants to open and release the essential oils that they produce.
Temperature of the steam must be regulated to allow the oil to be released, but not high enough to destroy the materials or burn the oils. The essential oils that are released evaporate and combine with the steam molecules to travel through the tube of the still and into the condensation chamber. The steam cools and condenses into water, leaving the essential oils floating on the surface to be decanted, or skimmed off.
The water that remains after the essential oils are removed is called floral water, distillate, or hydrosol. It may be used in skin care for facial mists or toners, as it retains many of the therapeutic properties of the plant from which it comes.
Cold Pressing
Cold pressing, or scarification, is another method of extracting essential oils. It is usually used to obtain citrus fruit oils like grapefruit, lemon, lime, mandarin orange, and tangerine. It is also the preferred method of obtaining carrier oils used to dilute essential oils.
During cold pressing the fruit rolls over a trough that contains sharp projections that penetrate the peel. These projections pierce the tiny pouches containing the essential oils. The entire fruit is then squeezed to release the juice from the pulp and the oil from the pouches allowing the oils to rise to the surface of the juice. The two are then separated by centrifugation.
Enfleurage
Enfleurage is a method of extracting essential oils from flowers that have such low contents of essential oils, or are so delicate, that heat would destroy them. It is a very expensive and length process in which flower petals are placed on trays of odorless vegetable or animal fat. This fat will absorb the flowers’ essential oils.
The flower petals are replaced as needed until the fat has been saturated with their essential oils. Alcohol is added to the enfleurage mixture to separate the essential oils from the fatty substance. When the alcohol evaporates the essential oil remains.
Solvent Extraction
Solvent extraction is another method used to extract a higher amount of essential oil from a delicate plant at a lower cost than the enfleurage process.
In this process a chemical solvent is used to separate the plant material and release the aromatic compounds. This produces a substance called a concrete, which is dissolved in alcohol to remove the solvent. The alcohol evaporates leaving behind what is called the absolute.
Unfortunately with this method, residues of the solvent may remain and cause side effects.
Turbo Distillation
Turbo distillation is a process in which plant material soaks in water and steam is circulated through the mixture. The same water is continuously recycled through the mixture during the entire process. This method is suitable for hard-to-extract or coarse plant materials such as bark, roots, and seeds.
Hydrodiffusion Extraction
Hydrodiffusion extraction disperses steam at atmospheric pressure through plant material from the top of a plant chamber. The steam saturates the plants more quickly and evenly than in a still. The resulting essential oils are also said to smell more like the original plant.
Carbon Dioxide Extraction
The final method of extracting essential oils involves using carbon dioxide under extremely high pressure. Plant material is placed in a stainless steel tank. Carbon dioxide is injected into the tank causing the pressure to build. The high pressure causes the carbon dioxide to turn into a liquid, which acts as a solvent to extract the essential oils from the plant materials. The carbon dioxide returns to a gaseous state when the pressure is decreased, and the essential oils are collected.
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