Foaming or cratering is the formation of bubbles and resulting small, round concave depressions in a paint film, during paint application and drying.

foaming and cratering

Possible Cause

Several things can cause foaming or cratering:

  • Shaking a partially filled can of paint.
  • Use of low quality paint or very old latex paint.
  • Use of a roller cover with wrong nap length.
  • Excessive rolling or brushing of the paint.
  • Applying a gloss or semi-gloss paint with a long nap roller.



All paints will foam to some degree during application; however, quality paints are formulated so the bubbles break while the paint is still wet, resulting in good flow and appearance. Use a quality synthetic roller sleeve (5mm nap for gloss & semi gloss and 12mm nap for low sheen and flat finish).

More problem solving advice

When droplets appear on acrylic paint

Have you noticed small droplets appearing on your fresh coat of acrylic paint? This is known as 'surfactant leaching'. Don't panic - it's a normal part of the curing process.  For each problem you’ll find a guide to identifying it, its causes and solutions.


Yellowing is the development of a yellow cast in aging solvent-based enamels. It’s most noticeable in the dried films of white paints or clear varnishes.  For each problem you’ll find a guide to identifying it, its causes and solutions.