2. Preventive conservation and storage

Storage in a cool, dry, clean, and stable location can extend the life of an item.[51] Manuscripts and paper documents are often stored in protective archival-quality boxes and folders, made of acid-free and lignin-free materials.[52] Documents with heavy use may be stored or encapsulated in a clear polyester (Mylar) film sleeve or folder. As added protection against acid formation, paper-based storage materials may have a buffer, such as calcium carbonate, which can neutralize acids as they form in the storage materials.[52] Boxes should not be overfilled. Items may be interleaved with acid/lignin-free paper.[43] If boxes are only partially full, spacers may be used, or the box may be stored horizontally.[2] Large format material is best stored in a plan cabinet with shallow drawers.[43] The rolling of large items (e.g. maps) should be avoided where possible; but if there is no other option, the item should be rolled around a large diameter archival quality tube.[53]

Average-size books should be shelved vertically, side-by-side so they can support each other.[51] Shelves should not be overpacked and should stand away from exterior walls. Oversized or fragile books may be stored horizontally and completely flat, but stacking should be kept to a minimum.[37] Books may be placed in supportive and protective boxes, to prevent soiling and abrasion and to provide structural support. Book boxes may range from simple four-flap enclosures made of archival safe paper or cardboard to custom clamshell or drop-spine boxes covered in book cloth.[51]