Uneven spread rate
Failure to properly prime a porous surface, or surface with varying degrees of porosity
Poor application resulting in lapping (see Lapping)
New substrates should be primed/sealed before applying the top coat to ensure a uniformly porous surface. Without the use of a primer or sealer, an extra coat of paint will more likely be needed.
Make sure to apply paint from 'wet to dry' to prevent lapping. Often, applying an additional coat will even out sheen irregularities.
Poor sheen uniformity is generally a result of inconsistent gloss levels and will appear as shiny spots or dull spots on a painted surface. It is also known as 'flashing'.
Yellowing describes the development of a yellow cast in ageing paint solvent-based enamels.
Wrinkling is a term to describe a rough, crinkled paint surface, which occurs when uncured paint forms a 'skin'.
Sagging is the downward "drooping" movement of the paint film immediately after application that results in an uneven coating.
