Paint cratering is the formation of air bubbles (foaming) and resulting small, round concave depressions (craters) when bubbles break in a paint film during drying.
- Shaking a partially filled can of paint or using too high a speed when using a drill mixer, introducing a lot of bubbles in the paint.
- Excessive brushing or rolling - applying a paint too rapidly - will drive excess air into the film.
- Use of a roller cover with wrong nap length.
- Applying a gloss or semi-gloss paint over a porous or unsealed surface.
- High heat during application speeds up drying; bubbles or craters that form will dry before they can break and level out.
- Using a thinner/reducer that is inappropriate for the coating.
All paints will foam to some degree during mixing and application; most paints are designed to allow these bubbles to break and flow smooth during drying.
Allow the coating to dry thoroughly, then sand smooth and repaint.
Slowly stir partially filled containers to prevent entrapping excess air in the coating.
If there is a very noticeable amount of air bubbles during application, try slowing down application speed.
Follow label and data page directions for the appropriate applicator. Determine the correct roller cover type or nap based on the coating being applied and the surface to be coated. Match the roller nap to the texture of the surface. On smooth surfaces, a 1/4" or 3/8" roller nap is usually sufficient. For a medium-textured surface, use a 1/2" nap. On rough or deeply textured surfaces, use a 3/4" nap or greater.
Prime porous surfaces before topcoating.
Follow label and data page directions for the appropriate environmental conditions.
Allow each coating to dry properly before topcoating.
Follow label directions for the appropriate thinner/reducer and amount to use.