BLISTERING:
Bubbles resulting from localised loss of adhesion, and lifting of the paint film from the underlying surface.

POSSIBLE CAUSES:
• Painting a warm surface in direct sunlight.

• Application of solvent-based paint over a damp or wet surface.

• Moisture escaping through the exterior walls (less likely with water-based paint than with solvent-based.

• Exposure of water-based paint film to dew, high humidity or rain shortly after paint has dried, especially if there was inadequate surface preparation.

• Multi coat blistering usually occurs when acrylic paints are applied over many layers of alkyd and acrylic paints; often when darker colours are used causing heat build up.

SOLUTION:
• If blisters go down to the substrate: try to remove the source of moisture. Repair loose sealants; 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 water-based exterior paint.

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