Herbal distillates are aqueous solutions or colloidal suspensions （hydrosol） of essential oils usually obtained by steam distillation from aromatic plants. These herbal distillates have uses as flavorings, medicine and in skin care. Herbal distillates go by many other names including floral water, hydrosol, hydrolate, herbal water and essential water.
Herbal distillates are produced in the same manner as essential oils. However, the essential oil will float to the top of the distillate where it is removed, leaving behind the watery distillate. For this reason perhaps the term essential water is more descript. In the past, these essential waters were considered a byproduct of distillation, but now are considered an important co-product. Much of the process of making and using herbal distillates was documented in Grace Firth's 1983 book entitled Secrets of the Still.
The science of distillation is based on the fact that different substances vaporize at different temperature. Unlike other extraction techniques based on solubility of a compound in either water or oil, distillation will separate components regardless of their solubility. The distillate will contain compounds that vaporize at or below the temperature that water boils. The actual chemical components of distillates have not yet been fully identified, but distillate will contain essential oil compounds as well as organic acids. Compounds with a higher vaporization point will remain behind and will include many of the water soluble plant pigments and flavonoids.
Herbal waters contain the beneficial products of essential oils plus more and in a less concentrated, safer form. Besides aromatic chemicals, these distillates also contain many of the plant acids making them skin friendly. With a pH between 5-6 they are great to use as facial toners. Cosmetics and toiletries makers are finding many uses for herbal distillates. They can be used alone as toners or room sprays. Distillates are also used as flavorings and curables.
Because hydrosols are produced at high temperatures and are somewhat acidic, they tend to inhibit bacterial growth. They are not however sterile. They are a fresh product, like milk, and should be kept refrigerated. Small-scale producers of hydrosols must be particularly aware of, and take steps to prevent bacterial contamination.