Appearance of a denser colour or higher gloss where wet and dry layers overlap during paint application.
Failure to maintain a "wet edge" when applying paint.
Maintain a wet edge when painting by applying paint toward the unpainted area and then back into the just painted surface. This technique (brushing from "wet to dry" rather than vice versa) will produce a smooth uniform appearance. It is also wise to minimize the area being painted, and plan for interruptions at a natural break, such as a window, door or corner (especially important when applying stain to bare wood). Alkyd paints generally have superior wet edge properties.