| Blistering: Blistering is the formation of bubbles
resulting from localized loss of adhesion and lifting of the paint film from
the underlying surface.
Possible Causes:
Painting in direct sunlight or on a surface that is too warm,
especially when applying a dark-colored solvent-based coating.
Application of an oil-based or alkyd paint over a damp or wet surface.
Excess humidity or other moisture escaping from inside through the exterior
walls (less likely with latex paints, which allow water vapor to escape without
affecting the paint film).
Exposure of a latex paint film to excessive moisture in the form of dew,
high humidity or rain shortly after the paint has dried, especially if there
was inadequate surface preparation and/or a lower quality paint was applied.
Solution: First, determine whether or not the blisters go all the way
down to the substrate. If they go down to the substrate, the problem may be due
to moisture coming from inside. Take steps to remove the source of moisture, if
possible. Repair loose caulk and consider installing vents or exhaust fans. If
the building has wood siding, install siding vents in areas where blistering
has occurred. Remove blisters by scraping and sanding, prime any areas where
bare wood shows, and repaint. If the blisters do not go all the way to the
substrate, the problem is probably not related to moisture coming from behind.
Rather, the blisters are likely from painting a warm surface in direct sunlight
or exposing the paint film to excessive moisture. In any case, sand, scrape and
then prime any exposed bare wood. Coat with a top quality acrylic latex
exterior paint.
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