The Problem: Foaming is the formation of air bubbles as paint is being applied. When these air bubbles break, small, round depressions can appear in the dried paint film.
Causes: Can include excessive shaking of the can of paint, applying the paint too rapidly, and using a roller cover with the wrong nap length. Using foam roller covers with today’s acrylic waterborne paints, as well as excessive rolling can also cause air bubbles.
How-to-fix: Use higher quality paints that are formulated so bubbles break while the paint is still wet, allowing the film time to flow and level out. Avoid excessive rolling or brushing of the paint, and use short nap rollers when applying gloss or semi-gloss paints. Finally, utilize an appropriate primer/sealer over porous surfaces, and sand problem areas before applying the top coat.