Gassing:-
The formation, in the can, of gaseous products in a coating material, due to the reaction between two or constituents of the coating material or between the latter and the metal of the container (see Putrefaction). Occurs in paints containing aluminium metallic pigments if moisture is present or acidity is too high. Special additives - moisture absorbents assist in minimising the problem.

Gloss Assessment
The gloss of a coating can be assessed by physical observation however the source of the light and the angle of observation cause differences. For reproducible results these must be controlled. Glossmeters measure the surface using 3 angles of incidence - 20º, 60º and 85º (from the vertical)

Grip Coat:-
A film of a coating material which, when applied to a substrate, bare or already painted, enhances the adhesion of a subsequent film of another coating material.

Hard dry:-
When a thumb (or substitute thereof) , exerting a measurable downwards pressure, leaves no permanent mark or damage on the coating film. It is the stage when the. paint film can be handled without damage.

Hardener:-
A material, generally part of a two component paint system, which reacts with the other binder component to produce a fully cured coating. Often wrongly called a "catalyst "

Hardness:-
The ability of a coating film, as distinct from the substrate, to resist cutting, indentation or penetration.

Haze:-
Haziness in film caused by the throw-out of components. Generally caused by wrong balance in thinners of diluent/solvents. See Bloom - internal.

Hiding power:-
A measure of opacity. It is the spreading rate at which a paint just obliterates a specified black and white surface when a film is applied according to a standard method; it is expressed in square meters per litre

Holding Primer:-
A low-build blast primer used to provide a temporary protection to steelwork until the complete paint system can be applied in accordance with accepted practice.

Humectant:-
A material capable of retaining moisture.