Lapping

Appearance of a denser colour or increased gloss where wet and dry layers overlap during paint application.

Possible Cause

• Failure to maintain a "wet edge" when painting.
• Use of low solids "economy" paint.

Solution

Maintain a wet edge when painting by applying paint towards the unpainted area and then back into the just-painted surface. This technique (brushing or rolling from wet to dry rather than vice versa) will produce a smooth, uniform appearance. It is also wise to work in manageable size areas and plan for interruptions at a natural break, such as a window, door or corner. Using a top quality water-based paint makes it easier to avoid lapping problems because higher solids (pigments and binder) content makes lapped areas less noticeable. If substrate is very porous, it may need a primer/sealer to prevent paint from drying too quickly, reducing wet edge time and therefore making lapped areas noticeable. Solvent-based paints generally have superior wet edge properties, and therefore less lapping.

Images courtesy of the Paint Quality Institute from Dow Coating Materials