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Michigan State University Extension
Home Maintenance And Repair - 01500037
06/24/03


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.

References

This article was written by Anne Field, Extension Specialist, Emeritus, with reference from the USDA bulletin, Mildew.

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