PIGMENT

Any fine solid particles that do not dissolve in the varnish and gives tha paint its colour and hiding power (or opacity). It can also contribute to the protective properties of the paint, in the top coat by helping resist the effects of the weather or in the primer where, for example, chromate pigments may be used to inhibit corrosion on the surface os steel.

Included in pigments is a group of materials called extenders. In the dry powder form they are of whitish colour, but when incorporated in the paint, they become translucent and therefore have poor covering power. They are so callled because one of their functions is to spread (or extend) the coverage of the coloured pigment.

Extenders are much cheaper than pigment and can carry out many useful function, e.g. improvement of adhesion, ease of sanding and film strength.

The pigment and extender powdwes are generally insoluble and consequently have to be mixed with or dispersed in the binders to form a suspension.