Navigate the murky waters of plant extracts, distillates, waters, hydrosols and essential oils in skincare with this quick guide. Learn to spot the difference between these compounds to enable you to make an informed skincare product choice.
The difference between essential oils / extracts / distillates / waters / hydrosols
The term ‘essential oils’ refers to aromatic compounds derived from plants mainly through steam distillation or solvent (a liquid that helps dissolving other molecules in order to make a solution) extraction, while hydrosols or floral waters are the condensate water derived from the distillation process. They even smell different because their chemical composition are poles apart. Sometimes floral waters or distillates are actually the waste water collected after washing the flowers, stems and leaves before they get processed. In rare occasions some suppliers even try to sell you just water combined with an essential oil and a solubilizer (Oh boy!).
All forms are equally valid as they all have their function and we formulators choose one or the other depending on their properties and the result we want to obtain. Some functional substances are soluble in oil like vitamin A, while others soluble in water like certain sugars that are highly hydrating.
Here’s a quick guide to the plant extraction process where solvents are used. A ‘solvent’ is a substance that dissolves functional molecules, resulting in a solution (extract):
Alcoholic: These are particularly rich in active ingredients, as alcohol, unlike water, is able to extract almost all of the phytocomplexes from the plant. Alcohol, in addition to having a superior solvent power, acts as an excellent preservative.
Ethereal: When you use only ethers such as Ethoxydiglycol.
Glycolic: Extracted with glycols, most of them are synthetic but there are some natural counterparts, such as butylene glycol or propylene glycol.
Aqueous: Simple extracts based on officinal herbs, these are the classic decoctions and herbal teas.
Hydro-glycerinates: Obtained by maceration in distilled water and glycerin.
Hydro-glycerol-alcoholic: Extracts obtained from a mixture of glycerin, alcohol and water.
Tinctures: Water and alcohol-based extracts using fresh plants (mother tincture) or dry (classic tincture).
Oleolites: Extracts in vegetable oils.
Dry plant extracts are presented as powdery preparations, but they cannot be considered powders. The latter, in fact, are obtained from by pulverization, without any extraction with solvent.
Enfleurage: A craftsmanship technique used by the perfume industry to obtain essential oils and essences from flowers.
Extraction with supercritical fluids: To extract specific compounds from plants where supercritical carbon dioxide is used. Its fancy name refers to an intermediate stage between gaseous and liquid states, in which the solvating and permeability capacities of the solvent are at their maximum.
Distillation: An extremely versatile method used for extraction and purification processes, which consists in the combination of two extraction variables: Pressure and temperature.
Maceration: The plant is placed in a container together with the appropriate mixture of solvents; from this type of extraction a fluid extract is obtained, called macerated.
Infusion: Where the solvent, boiling water, is poured directly on the ground up plant.
Decoction: Where the plant, together with the solvent, is heated for a period of time.
Percolation: Where the solvent, by gravity or under pressure, passes through a layer, generally homogeneous, of pulverized plant.
Cold pressed: A plant-based oil is typically cold-pressed from fruits, nuts, and seeds like in the case of olive oil.
How plant extracts are used in skincare formulation
Hydrosols, distillates and floral waters are frequently used in toners or when you want to increase the percentage of organic/natural matter by swapping out the water content in the formula. Essential oils have many properties but in skincare you should always be careful when you use them as their negative effects (irritation) can sometimes outweigh their benefits. Hence why they are usually used in very small quantities to perfume the final product or to mask the smell of other ingredients present in the formula.
Personally, when I formulate I choose tried and tested skin-friendly plant extracts that have been carefully studied for use on sensitive and reactive skins. This means selecting not only the most beneficial botanicals but also the most suitable extraction process as well. Once I am happy with the scientific results, I tend to use that extract in its maximum skin-safe quantity. I love using hefty doses of what really works on the skin.