A - Z list of keywords and terms from the coatings industry.


Water Based

A coating which is carried in water as the main liquid component. The coating resin may be dissolved in the water (although this is unusual), or it may be emulsified, or it may be dispersed in small particles.

Water Resistance

Coatings films absorb and transmit water and water vapour. Sometimes this property is used positively as, for example, in emulsion paints which allow new plaster to dry out through them, or microporous wood coatings which allow the wood to "breathe". Generally when formulating exterior coatings, the aim is to maximise the water resistance of the film.

Weathering Resistance

Coatings systems are broken down over time by the action of UV light, atmospheric moisture and acidity, and accelerated by infra-red radiation. For coatings to be used outside, it is important to slow the break down of the coating as much as possible. The is done by a combination of weathering-resistant binders and pigments, the use of special additives such as UV absorbers and the design of the coatings system itself, including its thickness.


A laboratory machine which replicates changes in lighting and atmospheric conditions, providing a greatly accelerated guide to the likely weathering performance of a coating.

Web Offset

A litho printing process, printing paper in a reel rather than sheet by sheet. Inks may dry by absorption into the paper, followed by oxidation ('cold set'), or by curing in ovens ('heat set'). Cold set is used primarily for newspapers, because newsprint offers rapid absorption of part of the inf. Glossier papers used for magazines, tourist brochures and catalogues are not so absorbent, and the heat set process gives a high quality of reproduction at high running speeds.

Wet Edge

The extremity of the coating which remains workable, particularly on a large surface.

Wet Edge Time

The time that a coating remains workable, allowing freshly applied coating to join up without showing.

Wet Film Thickness

Thickness of coating immediately after application.

Wet on Wet

Coating applied directly onto coating which has not dried.


The coating of pigment particles with thinner (not necessarily water) and resin.

White Spirit

A petroleum distillate used as a solvent and cleaner for alkyd and other resins, particularly for brushing applications.

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