If you have plans
to repaint a room but have discovered mildew stains, you definitely
need to treat the mildew before you paint, because it will
bleed through the new layer of paint.
You can use a commercially
available product to treat mildew on walls, the most commonly
used one called Kilz. However, you can make your own mildew
treatment at home to wash and treat mildew before painting.
In a bucket, mix
1 part bleach with 3 parts warm water. Using a rag or sponge,
clean the affected area, as well as a foot or two on each
side, to take care of any mildew that isn't easily visible.
Once dry, paint as normal.