A non-uniform appearance of color that occurs when a wall is painted with a roller and the edges (where the roller could not reach) are “cut in” with a brush. The brushed areas generally appear darker, thus resembling the frame of a picture. Sprayed areas may be darker than neighboring sections that are brushed or rolled.
Applying paint at different film builds (e.g. thickness of each coating layer) as a result of using a thick brush cut-in application versus a thin roller application. Spraying versus brushing may also show the problem because of differing film builds.
Don’t cut in the entire room before painting the larger areas. Work in smaller sections of the room to maintain a wet edge. When using a brush, only cut in as narrow an area as needed, usually 1″ to 2″, using the roller as close to the corner as possible.
Apply the coating as uniformly as possible with any application method.
All colors, including white, should be thoroughly shaken before use.