Hydro Vs. Steam Distillation

Written by holly huntington
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Hydro Vs. Steam Distillation
The distillation process can remove oil from plants for perfume. (Jeffrey Hamilton/Photodisc/Getty Images)

Aromatherapy requires the use of essential oils. Essential oils are created by extracting the oil from the plant. Extraction of the plant's oil can be accomplished through hydro distillation and steam distillation. The two processes share some similarities as well as differences, with steam distillation being the most commonly used process, according to Pioneer Thinking.

Essential Oil Distillation History

Essential oils are used for many applications today: beauty, flavouring, fragrance and health. Historically, essential oils were used for cooking cosmetics, incense, as medicine and for perfumes, as well as mummy preservation by the Egyptians, according to the University of Florida IFAS Extension. Distillation as the method of obtaining the oil from grasses, plants and trees initially began in the 18th century.


In both the hydro and steam distillation process, the time the raw plant material is left in the distillation machine -- regardless of which method is used -- along with the machine temperature and the pressure of the machine chambers, all influence the final essential oil product, as does the quality of the raw plant material used. The same types of raw plant materials are used in both processes: bark, blossoms, fruits, leaves, roots, seeds, and stems, although not necessarily each part for each essential oil distilled. And raw plants of all types are used in both processes, including annuals, flowers, grasses, herbs, mosses, shrubs and trees. But the process of extraction differs between hydro and steam distillation.

Steam Extraction

Raw plant material is placed into a steam distillation machine chamber. Steam is forced into the chamber with it. Plant air sacs burst, emitting plant oils, due to the pressure and temperature of the steam as it fills the chamber. The machine has an adjoining condensed chamber that is chilled. As the essential oil interacts with the steam, the steam flows into the chilled condensed chamber, turning back into a liquid, providing the essential oil.

Hydro Extraction

In the hydro extraction process, raw plant material is added to water, which is then boiled, producing steam. The steam produced is captured in the hydro machine and condensed. That product moves through the hydro distillation machine into another area, where the water and the oil produced are separated, creating two separate products: hydrosol (the water and some oil) and the essential oil. Hydrosol provides consumers with some essential oil properties, but at a reduced strength and impact.

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