Hydrosols are still a new product in the minds of the consumer and their potential only just recognized as an ‘active’ in the cosmetic and natural products field. If we are to give ‘value’ to the product as an active ingredient (which we do) then appropriate care must be taken that the activity is explicit in the product definition. Scented waters can be made in many ways and much of what is currently traded in the market is not true hydrosols but water with ‘scent’ added. This can be achieved by bubbling essential oils through distilled water, combining in a blender, diluting essential oils into water with dispersants and/or adding synthetic fragrance or flavor compounds to water, among other methods.

It is absolutely imperative that the term ‘hydrosol’ be defined in such a manner that the inherent active nature of the products is identified. Including parameters that establish minimum standards in production methods is a vital step in defining these products and creating a viable place for their exploitation. Further as we are talking about ‘organic hydrosols’ it is doubly important that we set high quality standards or we diminish the credibility and value of the very ‘organic’ standard. The ability to charge a premium for organic products is crucial to the economic viability of the practice. It has been clearly shown that natural products, particularly plants, grown by organic methods are superior in value and benefits to the consumer. These are values inherent in the plants make-up, vitamin content, food value, therapeutic qualities, and are over and above the value of being chemical free. The organic movement is based on these added values, it is what the consumer is buying. Inferior or non-active ingredients given a definition under the organic appellation will cause lasting damage to the status of all organics. Repairing lost position is far more difficult and costly than maintaining or enhancing status. Organic standards are about the long-term goals, the future views. Let’s define hydrosols in such a way that we can truly grow an industry that continues to stand for quality for years to come.

pH definition
Hydrosols must have an acid nature below 6.5 pH. The lower the pH the better the quality of the hydrosol and the more bacteriostatic the hydrosol will be. Hydrosols in the range of 5.0 pH up to 6.5 pH have a shelf of 6-12 months on average. Hydrosols with a 5.0 pH or less may have shelf life in excess of 20 months without the use of preservatives. The pH value of a hydrosol is a key factor to defining the product. Tests subsequent to the publication of Hydrosols: The Next Aromatherapy show that all hydrosols are at optimum concentration levels of botanical components when they are 6.0 pH or less, rather than the 6.5pH listed in the book. More than 75% of hydrosols currently in the market are acid in the 3.0 pH to 5.0 pH range.

If pH readings are taken of the distillate at regular intervals through the run a point will be reached after which a steady, irreversible rise in the pH of the water portion will be seen. The point at which the pH begins to rise is the point at which the distillate changes from a hydrosol, a product in it’s own right, into ‘water’ suitable for use as a non-ingredient status additive or in a variety of organic farming practices.

Any untreated* distillate product that is 6.5 pH or above should not be considered a hydrosol. And if the product reaches 7.0 pH then it should be considered water for ingredients purposes, regardless of odor or flavor.

*Untreated – contains no preservatives, additives, acidifers or other substances not present at condensation point.

Ratio definition
Organic production standards established in Europe have determined that hydrosol output from distillation can be 1 litre of hydrosol from each 1 Kg of plant material in the still. In actual fact, experience shows that optimum quality output is attained at a ratio of 1 litre of hydrosol from 2 or more Kg of plant. Unlike essential oils, which should be collected until the last drops have distilled over, the water soluble components present in the hydrosol and the essential oil ‘in solution’ distill over during the early stages of the run. If pH readings are taken during the distillation the pH will be seen to rise as the hydrosol chemistry becomes diluted and inactive.

Bearing in mind the non-water solubility of many essential oil components it is reasonable to assume that the plant variety distilled also affects to ratio of hydrosol output to material distilled. Some species like the conifer trees contain primarily mono-terpenes which are highly lipophyllic, only a small portion of the distillate (the first 10-20%) from these species is ‘active’ resulting in a high ratio. On the other hand cinnamon bark with it’s many water soluble ingredients will be remarkably strong and active at 1.5:1.

Weather may also affect the distillation ratio for hydrosols. In a wet year, when thee plants contain a higher proportion of water thee hydrosol yield should be reduced by 20-30% if the resulting hydrosol is to be stable and therapeutically active.

The following ratios have been established over more than a decade of research specifically on producing active therapeutic hydrosols for human use and consumption:

• Conifer tree and plants high in monoterpenes 7-10 Kg of plant to 1 litre of hydrosol
• Green leafy and herbaceous plants high in monoterpene alcohols 3-4 Kg of plant to 1 litre of hydrosol
• barks, woods and resins, high in sesquiterpenes and diverse chemistry 1.5-2 Kg of plant material to 1 litre of hydrosol.

Ratio of hydrosol output to plant material distilled is dependant on plant species and may alter slightly from year to year depending on weather.

Surface Tension
The two previous parameters lead us directly to this one. Providing the simplest, visual test for hydrosol quality, high surface tension reflects both lower pH and higher concentrations of water soluble plant chemistry. A small amount of hydrosol (1-2ml) poured on to the back of the hand should have sufficient surface tension to stay beaded on the skin. If the surface tension is low and the ‘bead’ flattens or the liquid flows off the hand, it is usually a sign that too much hydrosol has been collected from the run and that the later portions have diluted the earlier active portions as described above.

Tests on pH of these low surface tension ‘waters’ has revealed that they are usually 6.0 pH or higher. Late portion distillates collected in separate vessels are clearly identifiable from early portion distillate from the same run, in taste, aroma and acidity. Additionally there is never cloudiness or milkiness in late portion hydrosols as these effects are created primarily by essential oils in solution in the hydrosol and as the water soluble oil componenets often distill over first, the later distillate runs clear. Like water. Hydrosols have high surface tension reflecting high concentration of ‘active’ compounds.

On-Site
There are several simple tests that can be done “on-site” to determine hydrosol quality.

• pH read by digital meters with both 7.0pH and 4.0pH calibration fluids.
• surface tension of isolated hydrosol during distillation
• visual examination of output vs material distilled to confirm 1:1 ratio or better.