Drier

(engineering) A device to remove water.
(materials) A substance that absorbs water. A substance that is used to hasten solidification. Material, such as salts of lead, manganese, and cobalt, which facilitates the oxidation of oils; used in paints and varnishes to speed drying.

A material added to paint formulations to facilitate the oxidation of oils. Driers are salts of metals. Acids used to render metals soluble in oil, and therefore useful as driers, may be fatty acids, rosin, or naphthenic or octoic acids derived from petroleum. Cobalt, the most reactive of drier metals, is generally regarded as a surface drier, and it is widely used as the only additive in thin-film paint formulations. Lead, while less reactive than cobalt, may have increasing restrictions in its applications because of ecological requirements. Numerous other metals, including cerium and vanadium, have been used occasionally, and are effective driers. Certain organic compounds also catalyze the drying of oils and have been used for this purpose when freedom from all metallic contamination is required.

In general, small amounts of drier are essential to the formation of a satisfactory paint film within a reasonable time. Addition of large amounts of drier, however, can lead to premature embrittlement and failure of the paint film. See also Drying oil; Paint.