"Hydrosol" is the term for the distilled water that is separated from the essential oil at the
end of the distillation process. Hydrosol typically contains around 0.05% w/v of essential oil
that cannot be readily separated. This is because the oil particles are so small that they
manage to escape separation. Thus, hydrosol should contain a subtle aroma of the plant when
it is used.
distilleries re-use hydrosol in the water supply for subsequent distillations. At Stone Rise
Farm, we believe that this practice, due to the nature of steam distillation, can contribute
to a lowering of the quality of the resulting essential oil. Also, if the distillery is
marketing a particular variety of essential oil, for example Lavandula angustifolia
"Maillette", they would have to ensure the re-used hydrosol came from that variety when it
was distilled. Therefore, we do not do this.
- Some distilleries discard the hydrosol altogether. We believe that this
practice denies customers of the many uses for hydrosols, so we do not do this either. For more
information on the uses of hydrosols, please see the History & Modern Use page.
- IMPORTANT: Evaluating Hydrosol Aroma
- Due to the nature of the steam distillation process, hydrosol not only
contains some essential oil, but also some water-soluble plant compounds (plant acids etc.)
not present in the oil itself. These water-soluble plant compounds can give a "honey", "hay" or "grassy" aroma
when the hydrosol is first smelled or applied (sprayed on) to the skin or other surfaces
- To evaluate the aroma of a hydrosol then, the method is similar to perfume
- Using a scent strip or similar, apply enough hydrosol to the strip so that it is saturated. At this point you can smell the "Top Note" of the hydrosol
aroma, which includes the water-soluble plant compounds in the distilled water.
- Wait for the scent strip to dry off somewhat. At this
point, the distilled water and much of the water-soluble plant compounds have
evaporated, leaving the "Middle Note" of the hydrosol aroma in which the essential oil aroma will be more in evidence if the hydrosol is oil-rich.
- In our experience, there is virtually no "Base
Note" to hydrosol (in perfumery, "Base Notes" are typically smelled 30 minutes after
application). The "Middle Note" seems to persist in ever-decreasing levels of intensity as
application time elapses.
- Due to the nature of the essential oil
component of the hydrosol, the more you apply by repeating steps 1 and 2, the longer the
aroma will last, as there is then more oil on the scent strip.