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Distillation~ Hydrosol & Essential Oils

Updated: May 23, 2022

Steam distillation is a process that uses a still to combine material with water, and heat to yield fragrant liquid. The fragrant liquid is produced in distilling called "hydrosol", and has a very complex composition of volatile oils, water soluble constituents that were within the plant, water from inside the plant's cells, and water that was added to the still along with the plant material. The volatile oils (also referred to as "essential oils") are comprised of hundreds of compounds that will distill off at different temperatures and times during the distillation process. The volatile oils usually rise to the top of the liquid, as they are hydrophobic. They can be strained off for therapeutic use or remain with the hydrofoil in final containers. Both hydrofoil and volatile oils have therapeutic applications that vary depending on the plant being distilled.

Our bodies are designed to interact with plant fragrances, which we are concentrating in the distillation process. The volatile oils from plants, whether through distillation, rubbing a plant on the body, drinking a tea or smelling the volatile oils in the steam, travel through the nasal passage to the receptor neuron that transports it to the limbic brain, They are very fast acting in bringing about changes in our emotions, hormonal recreations, perception of pain, memory, and fight or flight response, all of which are influenced by the limbic system.

Guide to Distilling Hydrosols and Essential Oils

Is the plant ready to be distilled?

Like preparing other forms of herbal medicine, the first step in steam distillation is to pay attention to the conditions of the environment and the characteristics of the plant to deicide if it is ready to be harvested for distillation. Many factors influence the decision,. The time of year, where the plant is in its development (leaf, flower, fruit, seed, dormant), the outdoor temperature, precipitation and the time of day all influence the quality of the distillation product (Ring, 2015). This is part of the "art" of distilling.

Choosing a method of distilling

Two main methods exist for steam distilling: hydro-distillation and steam distillation:

Hydro-distillation involves placing the plant directly in the water.

Steam distillation involves placing the plant above the water so that only the steam passes through the plant tissue.

Two can be combined as well, with the still being half-filled with water and part of the plant material immersed in the water while part of the plant is suspended above the water.

Packing the still

Plant material will need to be prepared by removing debris and dirt, unwanted stems and aged material, and then cut into the size that you desire to allow for the water/steam to more fully surround the plant tissue. Clean fresh water is added to the still. The plant material is then placed in the pot and onion of the still if hydro.steam combined distillation is desired. A small amount of space is left in the bottom to prevent the plant material from burning,(For dense material, the plant can be soaked in the water in the still to help break down the fibrous or waxy parts of the plant prior to running the still through an entire cycle. This can be done by soaking for a few hours or overnight).

Running the still

The beginning~ The condenser is filled with cold water and the still is turned on high. Sterilized containers are placed near the still to catch the distillate.

Temperature of the burner~Turning the burner down as low as possible to maintain a steady drip of distillate. Particular plants will like a hotter temperature, like Cedar and Rosemary.

Temperature of the condenser~The condenser temperature will influence the character of the distillate as well. If the condenser is too hot then some of the essential oils will not condense and will be lost as a vapor. This can usually be smelled or seen when distilling. If the condenser is too cold, then some of the essential oils will condense and stick to the inside of the coil. The top of the condensing unit should feel warm and the bottom should be cool.

Range of aromatics and therapeutics over time~ The compounds that were distilled shift over time while running the still. This is detectable by scent, taste and placing the distillate on the skin. Soft, light, bright, floral notes are usually noticed in the beginning of the run while it shifts to deeper, earthier, woodier, grassier aromatics as these become soluble in the water and volatize.

The end~ The distillation run is complete when the aromatics have shifted into qualities that are not desired.


Harman, A. (2015). Harvesting to Hydrosol., Fruitland, WA: IAG Botanicals

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