Always launder or dry clean linen before storing.
Soiled linen encourages mildew, so linens must be clean before storing. Ventilation, light and lack of available food discourage mildew growth. If mildew does attack your linens, brush the mold off outdoors to avoid scattering spores in your house. Then soak the linen item in a solution of oxygen bleach and water before laundering. If possible, dry in the sun.
Be sure to rinse thoroughly all soap and detergent from linen items to avoid formation of "age spots," caused by the oxidation of cellulose, linen's primary component.
Store in a cool, dry, well-ventilated area.
Use pure linen, cotton or muslin, not synthetics, as covers or garment bags.
Use acid-free tissue paper, not regular tissue paper. The acids in regular tissue paper can yellow linen.
Do not store linens in plastic bags, cedar chests and cardboard boxes. Fumes from petroleum-based polyurethane can rot and streak the fabric. Cedar fumes and the acids in unvarnished wood yellow linen, as does the acid in cardboard.
When storing for a long time, refold the linen occasionally.