Lap Marks are the appearance of a denser color or an increased gloss where wet and dry layers overlap during paint application.
Note: Image provided by The Paint Quality Institute
What Causes Lap Marks?
Failing to maintain a “wet edge” is the most common cause of lap marks. Using “economy” paint or not priming a porous surface can also both lead to the formation of lap marks.
How to Prevent Lapping
When painting, make sure to maintain a wet edge by applying paint toward 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 manageably sized areas, and to plan for interruptions at a natural break, such as a window, door, or corner. Using a top-quality acrylic latex paint makes it easier to avoid lapping problems. If the substrate is very porous, you should apply a primer or sealer to prevent paint from drying too quickly and reducing wet-edge time. When working on exteriors consider Benjamin Moore’s extender to increase open time and finish coat quality. It is made with 100% acrylic resin.