A newsletter reader sent me a link to an online article that made me shudder when I read it. The article claims:
“Do you have an old book or important document that has been passed down from generation to generation? These books and documents break down over time due to oxygen, moisture, and other hazards. By sealing it, you’re also giving it added protection in the event of a flood, fire (smoke), or accidental damage.”
I am no expert in preservation, but I believe the last thing you want to do to a valuable old book or photo or other document is to seal it in an airtight plastic bag, especially a bag that is not labeled "archival quality." Sealing in a cheap plastic bag can cause more damage than it prevents!
Paper, photographs, film, and tape are all made from materials that change over time. When these materials change, they will leach chemicals or give off gases that will loop back and inflict self damage if they are “sealed in their own juices.” Your books, photographs, and documents will last much longer if they are exposed to the air, where the chemicals and gases can dissipate. Storage temperatures between 60 and 75 degrees and humidity levels between 50 and 60 percent are ideal.
Archival plastic enclosures can be made from polyester, polypropylene, or polyethylene. Don't use any plastic that is not one of these three, and don't use anything that is not labeled "archival quality." Also, never seal it.
You can read advice written by Sherelyn Ogden, Head of Conservation for the Minnesota Historical Society, at Storage Enclosures for Books and Artifacts on Paper at https://www.nedcc.org/free-resources/preservation-leaflets/4.-storage-and-handling/4.4-storage-enclosures-for-books-and-artifacts-on-paper.