Interior Paint Problem Solver
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Black, gray, or brown spots on the surface of paint or caulk.
Forms most often on areas that tend to be damp, or that receive little or no direct sunlight (e.g., bathrooms, kitchens and laundry rooms).
Use of an alkyd or oil-based paint, or lower-quality latex paint.
Failure to prime a bare wood surface before applying the paint.
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 area. If it is bleached away, the discolorant is probably mildew.
Do not paint over a mildewed surface as it will grow through any new coat of paint.
Remove all mildew from the surface by scrubbing with a bleach solution (one part bleach, three parts water), while wearing rubber gloves and eye protection. Rinse thoroughly.
To protect against mildew in high humidity areas, use a quality kitchen and bath paint. Also consider installing exhaust fans in these areas.
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