Blistering

Bubbles resulting from localized loss of adhesion and lifting of the paint film.
 Blistering
Blistering

Blistering

(The formation of bubbles or pimples on the painted surface caused by moisture in the wood, by painting before the previous coat has dried).

Bubbles resulting from localized loss of adhesion and lifting of the paint film from the underlying surface. There are 2 kinds of blistering, caused by heat and caused by moisture. Caused by heat: Painting on a surface hat is too warm will cause the film to dry too rapidly, and trap solvent that later vaporize. This will create pressure against the topcoat creating blistering. Caused by moisture: Alkyd finishes are sealer type finishes and do not allow moisture to vaporize. High temperatures, during the summer, will cause moisture to vaporize faster than the alkyd finish coats will allow this moisture to escape.

Possible causes

  • Applying oil-based or alkyd paint over a damp or wet surface.
  • Moisture seeping into the home through the exterior walls (less likely with latex paint).
  • Exposure of latex paint film to high humidity or moisture shortly after paint has dried, especially if there was inadequate surface preparation.

Solution

  • Old paint should be completely removed by scraping and sanding the surface; a heat gun or power washing can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with high quality latex or oil-based primer, and then painted with a top quality paint.