CAUSES: Small depressions in dried paint film are caused by pockets of air or entrapped solvent in the wet paint film. These depressions can occur during application. In the case of solvent entrapment, they occur shortly after the intermediate coat or topcoat has been applied over the primer coat. They also can result from top-coating a solvent-based product too quickly, using a new roller cover without proper preparation, over-shaking the paint of painting in excessively high temperatures. Improper use of solvents when thinning the coating may also cause cratering.
SOLUTIONS: Craters should be sanded out and the surface repainted. If they are not removed before the new coat is applied, they will show through. Before using new roller covers, immerse them in the paint and roll them out a few times to expel air. After a can has been shaken, it should be left to sit until all bubbles and foam disappear.
Sometimes when painting on a hot day, the coating will dry too quickly and prevent the bubbles from flowing out during application. If this occurs, try adding a small amount of thinner to the paint.