In damp summer weather, keep papers and books as dry as possible to help control mold growth. If you have an enclosed bookcase, keep a small electric light lit continuously in the bookcase or use a chemical dehumidifier, keeping the doors closed as tightly as possible.
Remove any dry,loose mold from paper with a clean, soft cloth. If mildewed paper is damp, dry it first--in an airy place, if possible.
To dry wallpaper, heat the room for several hours or even days to dry the plaster as well as the paper. Plaster should be dried slowly to prevent cracking.
If mildewed paper is washable, wipe it gently with a cloth wrung out of thick soapsuds, then with clear water. Take care not to wet the paper more than necessary. Do not scrub it. Finally pat with a soft, dry cloth. If stains remain, bleach with a solution of a household bleach, then sponge with a cloth wrung out of clear water. For small stains, a commercial ink eradicator may be useful.
Spread pages of books out fanwise to air. If the books are very damp, sprinkle cornstarch or talcum powder between the leaves to take up the moisture. Leave starch or powder on for several hours then brush off.
This article was written by Anne Field, Extension Specialist, Emeritus, with reference from the USDA bulletin, Mildew.
Source: MSU Extension