There are many ways to extract essential oils and require elaborate equipments. These techniques are based on the fact that majority of the essential oils mix with oils, fats, alcohol, and certain solvents, but not with water. Some methods are more suitable for certain plants than others, depending on the plant's chemical make-up.
Therapeutic-grade essential oils which are the purest form of essential oils are usually extracted through a low-heat steam distillation process in which steam is circulated under pressure through freshly picked plant material thereby liberating the essential oils into the steam. The steam mixture is rapidly cooled causing it to condense back to water. The water and oils naturally separate and the oil is collected in its pure form. In order to ensure the highest quality oil extract of correct chemical composition, temperature and pressure must be monitored very closely. Too little heat and pressure will not release valuable oil whereas too much can change an extract's composition and potency.
Careful selection of the correct plant and plant parts harvested at the right time is also required for a successful extraction. This complex process is as much art form as it is science and requires experienced growers and distillers working together to ensure a quality product.
Fact: 12,000 rose blossoms are required to distill 5 ml of therapeutic- grade essential rose oil
A byproduct of this distillation is the remaining water. Some plants contain aromatic compounds that are also water soluble, they remain in the water that is left over after distillation. Such waters are very fragrant and are prized by aromatherapists, who refer to them as hydrosols. In aromatherapy, hydrosols are used mostly in cosmetics to moisturize skin.
Steam distillation is by far the most common method of extraction, but some oils are extracted through a process of compression in which the oil is squeezed from the plant's flesh, seeds and skin. This technique is used mostly with citrus peels, such as orange, lemon, lime, or grapefruit, because the oil in their peels is easily pressed out.
A very few essential oils are extracted using solvents that bind with the oils and are later removed from the final product.. First, the plant is dissolved in a solvent such as benzene, hexane. The solvent, which has a low boiling point, is then evaporated off. The resulting oils are called "absolutes". Even though the evaporated solvent is recaptured and cooled back into liquid so that it can be reused, this process is still expensive. As a result, it is reserved for costly oils that cannot be distilled, such as jasmine and vanilla, or for rose essential oil.