Mould is the black, grey or brown spots that can appear on the painted surface.
Mould forms most often on areas that tend to be damp, or receive little or no direct sunlight (e.g. bathrooms, kitchens and laundry rooms)
Use of flat or matt paints in areas subject to moisture
Use of low 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 fully removed
Test for mildew by applying a few drops of household bleach to the area; if it is bleached away, the discolouration 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 premium quality water-based paint, and clean when necessary with bleach/detergent solution. Consider installing an exhaust fan in high moisture areas.
If the area is subject to frequent moisture, e.g. bathrooms, consider using Wash&Wear® +Plus Kitchen & Bathroom.