Absolute

The concrete is stirred with ethanol, often with gentle warming, until the aromatic part dissolves. The mixture is then deeply chilled, usually below 0 °C, so the waxes set and separate. The waxes are filtered off, the washing is repeated if needed, and the ethanol is distilled off under vacuum so the aromatic part is not heated for long.

A 2003 study of rose absolute tested 96% and 80% ethanol at minus 20 and minus 25 °C. Both temperature and ethanol strength changed the yield and the composition of the absolute. Two absolutes of the same species can differ simply because of how they were washed.

In Grasse, the sequence of concrete, ethanol wash, chilling, filtering and vacuum concentration has been the way to make flower absolutes since the late 19th century. The same steps are applied to pomades, and to CO2 extracts when residual waxes need removing.

Absolute yield is normally expressed against the concrete. For Damask rose the 2003 study recovered 58 to 64%. For jasmine, yields of 50 to 70% are reported. Counting back to the flowers, the Grasse page records about 800 kg of May rose per kilogram of absolute.

A 2012 Indian study made jasmine absolute by washing the concrete with cold methanol instead of ethanol and obtained 0.27% on fresh flowers, from 0.35% concrete. For jasmine, the wax lost at the washing step can be small.

An absolute may carry traces of two solvents: the first-stage solvent, usually hexane, and ethanol. Producers measure residues by gas chromatography and report them on the technical data sheet. The specific hexane limit for a perfumery absolute depends on each supplier's and customer's specification.

IFRA is explicit about two older solvents. Benzene is prohibited as a fragrance ingredient and must not exceed 1 ppm in the fragrance mixture. Toluene is also prohibited, with a 100 ppm ceiling. Since benzene was once used to extract flowers, old or undocumented absolutes warrant questions about the solvent.

Some absolutes have their own IFRA Standard. Oakmoss extracts are restricted because of atranol and chloroatranol. Peru balsam absolute is restricted, while the crude balsam is prohibited. Jasmine and rose absolutes are not restricted by name, but constituents such as benzyl alcohol and eugenol count towards their own limits.

IFRA limits on this page follow Amendment 49 (2020) and are unchanged in the 51st Amendment (2023). Check the current amendment before use.

Not every absolute passes through a concrete. Tonka, vanilla, labdanum and benzoin are dry materials, so the first step gives a resinoid, and washing that resinoid with ethanol gives the absolute. Some producers extract directly with ethanol so the product can qualify for organic certification.

Under ISO, an absolute may also be made from a supercritical CO2 extract. A label that says absolute should prompt one question: absolute of what.