Black, gray or brown spots or areas on the surface of
paint or caulk.
Forms most often on areas that tend to be damp, or receive
little or no direct sunlight (bathrooms, kitchens and
Use of an alkyd or oil-based paint, or lower quality latex
Failure to prime a bare wood surface before applying the
Painting over a substrate or coating on which mildew has
not been removed.
Test for mildew by applying a few drops of household
bleach to the areas; if it is bleached away, the
discolorant is probably mildew. Remove all mildew from the
surface by scrubbing with a diluted household bleach
solution (one part bleach, three parts water), while
wearing rubber gloves and eye protection. Rinse
thoroughly. To protect against mildew, use a top quality
latex paint, and clean when necessary with
bleach/detergent solution. Consider installing an exhaust
fan in high moisture areas.