Probable Causes. Blistering is the result of gases or liquids (usually water) forming under the coating. The most
common cause of blistering on wood surfaces is the application of paint over a damp or wet surface. The breaking of the
blisters may result in a peeling of the paint coat. Blistering is also caused by using a paint that is incompatible with that
used in a previous coating.
Corrective Measures. Use a wire brush or scraper to remove all defective paint. Permit the surface to dry
thoroughly, then repaint.
Characteristics. A surface on which blushing has occurred is characterized by a white discoloration in the coating
and sometimes by the separation of ingredients from the coating. Blushing most commonly occurs in nitrocellulose
Probable Causes. Blushing may be caused by condensation of moisture on the film or by improper composition
of the vehicle (pigment-carrying liquid portion of paint) or solvent.
Corrective Measures. Remove or sand the film where blushing has occurred and repaint (after insuring that the
surfaces are dry). Blushing on acrylic lacquer may be prevented by adding acrylic lacquer retarder to the liquid lacquer.
Characteristics. Chalking can be detected by the existence of dry, loose powder on the paint film. Rain tends to
wash this powder off of exterior surfaces.
Probable Causes. The chalking of a painted surface is governed partially by the composition of the paint.
Chalking, loss of luster, and deterioration of the surface film are also affected by atmospheric conditions. Paints low in
binder content, or high in inert pigments, have a tendency toward early and excessive chalking.
Corrective Measures. A paint which chalks moderately affords a better repainting surface than one which does
not chalk at all; however, if excessive chalking has taken place, remove all the loose and powdery substance from the
surface with a wire brush and repaint.
5-25. CRACKING, FLAKING, SCALING, AND PEELING
Characteristics. Breaks which extend through the paint film to the bottom surface are called cracks. Cracking is
usually followed by flaking, scaling, or peeling. Flaking is the dropping off of small pieces of the paint coat. Scaling is an
advanced form of flaking and is evidenced by larger flakes. Peeling is the curling and dropping off of relatively large
pieces of paint film.
Probable Causes. Paints which become brittle when dried cannot contract or expand with moisture and
temperature changes, and are very susceptible to cracking. Cracking may also be caused by too many coats being built
up due to previous painting. Cracking advances to scaling and peeling as the old paint, which has lost its elasticity and
much of its adhesive grip, is pulled loose by the surface tension of the new paint film as it dries. Low grade paints usually
lack elasticity because they are deficient in oil and contain too much inert material for extended exposure. Since flaking
and scaling are usually preceded by cracking, their causes are much the same as for cracking. Scaling and peeling
frequently occur when paint has been applied to unseasoned or damp lumber. Peeling may also occur around knots, and
where cracks in the paint permit water to get behind the paint film.
Corrective Measures. Use a wire brush to remove all loose paint. In the case of cracking, remove the entire paint
coat using a scraper or paint remover. Clean the surface thoroughly with a duster before repainting, and be sure that the
first coat is thoroughly dry before applying a second coat.