Causes of mildew
Mildew is a thin, usually black, sometimes white,
growth produced on many kinds of surfaces by molds. Molds
are simple plants belonging to the group known as fungi.
Though molds are always present in the air, those that
cause mildew need moisture and certain temperatures in
order to grow. They commonly develop in humid summer
weather, especially in houses that are closed. They grow
fastest at temperatures between 75 F. and 85 F. Sunlight
helps kill mildew.
These molds grow on anything from which they can get
enough food. In homes they develop most often on cotton,
linen, rayon, silk, wool, leather, wood, and paper. Many
synthetic fibers are resistant to mildew.
Molds that cause mildew flourish wherever it is damp,
warm, poorly lighted, and/or where air is not
circulated--in cellars, crawl spaces or houses without
basements, and clothing closets; on draperies and rugs in
basement recreation rooms, on shower curtains, and on damp
clothes rolled up for ironing. These molds are also likely
in a newly built house because of moisture in the building
materials.