Bubbles resulting from localized loss of adhesion, and lifting of the paint film from the underlying surface.

• Painting a warm surface in direct sunlight.
• Application of oil-based or alkyd paint over a damp or wet surface.
• Moisture escaping through the exterior walls (less likely with latex paint than with oil-based or alkyd paint).
• Exposure of latex paint film to dew, high humidity or rain shortly after paint has dried, especially if there was inadequate surface preparation.

• If blisters go down to the substrate: try to remove the source of moisture. Repair loose caulking; consider installing vents or exhaust fans. Remove blisters (see Below). If blisters do not go all the way down to the substrate: remove them by scraping, then sanding, prime bare wood and repaint with a quality latex exterior paint.