From http://www.78rpm.com/faq.htm
How do I store my records?
Most vintage records have proven to be remarkably durable over time, but they do have enemies: dirt, moisture, pressure and temperature extremes.
If possible, records should be cleaned before storage. Dirt will scratch records, dust in the grooves will cause premature groove and stylus wear, insects and organic compounds will react with the shellac and silverfish eat sleeves and record labels. Once records have been cleaned, it is best not to put them back into old sleeves. New sleeves for storing records are available from Nauck's, and should be used if you care about your collection.
Records should never be allowed to get wet, and even high humidity can be dangerous. Sleeves absorb moisture which promotes mold growth. More importantly, organic filler material was often used to give strength to the otherwise brittle record groove. This filler material will erupt into microscopic blisters if it absorbs water, and that creates a grainy surface which results in the frying bacon sound frequently associated with 78s. So keep the records high and dry at all times.
Try to avoid storing your records flat, as this will cause grains of sand, record sleeves and other foreign objects to impress themselves into surface. Records should be stored upright on edge. Do not allow them to lean, and avoid keeping them in record storage boxes unless the discs are fully upright and flat against each other. They may be safely stored horizontally if the individual stacks are not greater than a couple of inches tall and the temperature doesnt get too high.
High temperatures quickly damage records, so it is important to monitor the environment where your records are stored. Ideally, the ambient temperature should not be allowed to exceed 75° F, especially if the records are not clean and stored upright!
Several internet merchants sell acid-free sleeves.
Albert