Mildew is presented as black, gray or brown spots or areas on the surface of paint.

Mildew forms most often on areas that tend to be damp or receive little or no direct sunlight such as bathrooms, kitchens and laundry rooms.

It could be cause by the use of oil-based paint in areas with o ventilation, failure to prime a bare wood surface before painting, painting over an affected mildew surface with out removing it first.