Downward movement of a paint film during application and setting, resulting in an uneven film having a thicker lower edge. In this example rough scratch plaster hollows trap more paint and result in runs.
Possible Causes
Too thickly applied coat due to incorrect roller cover or technique.
Paint with poor flow properties
Incorrectly thinned paint
Painting in too cold or humid conditions
Spraying to close to the surface.
How Can I Fix This Problem
If still wet; brush or roll out to level.
Dried paint needs to be sanded level and repainted. Make sure that the paint and application technique match the original.
Don’t paint in excessively cold or humid conditions.