Concrètes and Absolutes are concentrated aromatic materials extracted from plants in a multi- phase process. The first phase is extraction of the aromatic constituents from the plant material using a solvent such as hexane. When the hexane is vacuum-removed, it leaves behind a semi-solid to solid and highly fragrant material called a concrète that is comprised of a large amount of pigments and waxes. Due to their waxy texture, concrètes are perfect for making solid perfumes. They have somewhat delicate, yet long lasting aromas and are soluble usually in both carrier oils and alcohol, though often it is necessary to filter out any insoluble waxes and/or solid materials that remain.
In the second phase, aromatic oils are extracted and separated from most of the plant waxes and non-aromatic materials as the concrète is washed in ethyl alcohol, followed by filtration and/or centrifuging; the alcohol is recovered by gentle vacuum. The remaining aromatic material is called an absolute. Absolutes are the most concentrated form of botanical fragrance, highly regarded in natural perfumery, with an aroma close to that of the living plant material. Absolutes still contain some waxes and pigments along with other constituents from the plant, but are mostly comprised of the concentrated aromatic material that can range in consistency from mobile to quite viscous and even solid. In addition, they usually contain a small percentage of alcohol remaining from the second phase of the extraction process (typically up to 2 or 3 percent).
Absolutes differ from essential oils in that essential oils do not contain waxes, tend to be much lighter in color or have no color, and have comparatively lighter aromas. While essential oils are excellent choices for skincare and for therapeutic applications, absolutes and concrètes are reserved for use in natural perfumery.