Moisture trapped beneath the paint film due to:

  • Improper dry time after wet sanding;
  • Contaminated air lines;
  • Spraying in extreme high humidity conditions.
  • Using a poor grade and/or too fast evaporating thinner/reducer for spray conditions.
  • Trapped solvents from applying wet heavy coats with insufficient flash time between coats.
  • Improper dry time of undercoats before topcoating.
  • Painting over grease, oil or rust.


  • Remove affected area and refinish.
  • Extreme cases must be stripped to bare substrate before refinishing.


If wet sanding is preferred, allow sufficient time for moisture to evaporate. Avoid wet sanding lacquer type primer surfacer when possible. Drain moisture from compressor and air lines regularly. Allow additional flash time between coats and/or add retarder when spraying in humid conditions, or spray at times of low humidity when possible.

  • Select proper thinner/reducer for spray conditions.
  • Apply materials according to product recommendations, allowing sufficient flash time between coats.
  • Allow undercoats to thoroughly dry/cure before topcoating.
  • Clean and prep substrate using recommended products and procedures.