| Mildew: Mildew is the formation of brown, black or
gray spots or blotches on the surface of paint or caulk due to the presence of
fungi that feed on the paint film and other organic matter.
Possible Cause:
Damp areas that receive little or no direct sunlight (thus,
such areas as walls with a northern exposure and the underside of eaves are
particularly vulnerable).
Use of a lower quality paint with an insufficient amount of mildewcide.
Painting over a substrate or coating on which mildew is present.
Failure to prime bare wood before painting.
Solution: First, make sure that the discoloration really is mildew,
and not just dirt. Apply a few drops of household bleach to it, wait five
minutes, then rinse. If the dark color disappears, the discoloration is
probably mildew. Remove all mildew by scrubbing with a diluted household bleach
solution (one part bleach, three parts water). Be sure to take the proper
safety precautions -- wear rubber gloves and eye protection. Leave the bleach
on the surface for several minutes, then rinse. Next, thoroughly clean the
surface with a detergent solution to remove dirt and other organic material on
which mildew can feed. This can be done by hand or with a power washer. Rinse
again. When the surface is dry, apply one or two coats of top quality acrylic
latex paint -- this type of paint contains extra mildewcide and will resist
mildew better than oil-based or alkyd paints.
|