Extraction & solubility

Extraction brings selected constituents out of a starting material. In botanical skincare and perfumery, that might mean steeping flowers in oil, making a tincture or collecting aromatic material through distillation.

A plant contains many constituents: the individual substances that make up its tissues, pigments, aromas, oils and other materials. Each preparation gathers a particular portion of that chemistry.

Why the medium matters

Solubility describes how much of a substance can dissolve in a particular medium under given conditions. Sugar dissolves in water; oil behaves differently. Plant constituents have their own affinities for water, alcohol and oils.[1,2]

The material doing the dissolving is called a solvent. Water is a solvent too. In an infused facial oil, the oil serves both as the extraction medium and as part of the finished product.

Temperature, time, particle size and the proportions of plant material and solvent also influence extraction. Changing the alcohol-to-water ratio, for example, can change the balance of constituents recovered.[3]

Different methods, different preparations

Water infusions, oil infusions and tinctures keep plant material in contact with a liquid. Distillation collects constituents that travel with vapor. Pressing mechanically releases oils, while CO₂ extraction uses pressurized carbon dioxide as a solvent.[4,5,6,7,8]

Some extraction media remain in the preparation, as oil does in an infusion. Others are removed to leave a concentrated extract, as in the production of an absolute.

The plant, plant part and preparation together tell us much more about an ingredient than the plant name alone.

Related entries: Water infusions & decoctions; Oil infusions; Tinctures; Distillation; CO₂ extracts; Absolutes; Resinoids.