Protective Enclosures

Library materials inside a protective enclosure


Protective enclosures keep the parts of an item together, provide some physical and chemical environmental buffer, provide physical support to an object for storage, and provide an auxiliary surface for labeling. Many standard-size enclosures are available from commercial vendors, but we also provide custom enclosures when standard enclosures are not available or appropriate. Enclosure materials and structures vary widely and may include envelopes, sleeves, folders, dust jackets, boxes, and portfolios. Protective enclosures are available for a wide variety of formats found in library and archival collections. See below for more information.

Books and Bound Items

Bound items may become candidates for receiving protective enclosures in several ways. Bound items which are damaged and have paper too fragile to repair are often best served by being housed in a custom-sized box or portfolio. Library items with multiple parts can be kept together safely in an enclosure. Some binding structures (for instance, spiral bindings) do not survive well in the stacks unless given a protective enclosure.

The exact structure of the enclosure used will vary based on the size and type of the item. For smaller or thinner items, a portfolio or wrapper made of a lightweight board might provide the best protection. For medium-sized books, a phase box made of thicker board is a good solution. For very large or thick items, a clamshell box made of corrugated board or heavier material is likely to provide the best support. Custom enclosures can be outfitted with pockets, dividers, or insets to accommodate materials of multiple shapes and formats in the same enclosure so that all the parts of an item can be kept together.

Preservation Services makes custom-sized enclosures in a variety of structures for the Harvard Library. For more information, please contact Collections Care. For special collections, please contact Weissman Preservation Center.

Protective Storage Guidelines for Paper-Based Materials

Paper-based materials are placed in enclosures to provide protection, support handling, and isolate one item from another. The enclosed items are then placed into archival storage boxes or flat file drawers to further protect them from exposure to light, airborne pollutants and dust, and to minimize the effect of rapid fluctuations in temperature and humidity. In selecting an enclosure there are many factors to consider: choice of material, storage orientation, standardized dimensions of enclosures and storage boxes, and the number of items per enclosure.

Paper folders are the most commonly used enclosures. A folder is typically a sheet of paper or thicker "folder stock" folded in half with the fold along the long dimension. Folders can also be made from rigid materials such as archival corrugated board and mat board joined with archival tape. Folders should be made of acid-free, lignin-free, and buffered (alkaline) paper stock. The highest-quality paper stock also passes the Photographic Activity Test (P.A.T.) See section below (Enclosures for Photographic Materials) for more information about the P.A.T.

Polyester film enclosures are transparent and have the advantage of allowing one to view the item without opening the folder. A common enclosure design has a weld or seal along two adjacent sides, in the shape of an L. The paper item is slipped into the folder, positioning one seal along the bottom. One disadvantage of polyester is that it generates static electricity, making it unsuitable for friable media such as graphite, charcoal, and pastel. Polyester is also expensive and heavy compared to paper products. Polyester enclosures, however, are often ideal for fragmented or severely torn items where the static charge is an aid in keeping loose pieces together until the item can be repaired.

Storage orientation is an important consideration. When possible, paper items should be stored flat (horizontally) within a storage box to distribute their weight evenly, reducing the risk of deformation to the items within the box. Vertical storage is frequently used for archival or manuscript material, when the items can support their own weight, and when a collection has a mix of formats, such as pamphlets and single sheets in the same box. To keep the enclosures and items upright, manuscript box spacers are used to fill any empty space and prevent slumping and curling of the items.

Standardized dimensions of enclosures and storage boxes are more economical and provide consistency for handling. The dimensions of the enclosures should be the same as the box in which they are stored to minimize movement of the items within the box. For example, 16 x 20" folders should be in a 16 x 20" storage box. Even when different-sized items are stored together in one box, their enclosure dimensions should be the same and large enough to fully cover the largest item in the box. Purchase standard-size boxes and enclosures in a range of dimensions that fit your collection needs. Custom dimensions are available as well. When paper items are to be stored in flat files, for economy of space you may designate drawers to be used for full drawer-size enclosures and subdivide other drawers to accommodate half-size or even quarter-size enclosures.

The number of items per enclosure is also important to consider. Ideally, there should be only one item per folder. When this is not practical, do not exceed ten items per folder. Items of different sizes stored together in a folder should be interleaved or subdivided if possible.

Many enclosure variations are possible. If the enclosure material cannot adequately support the item, one can place an additional support directly beneath the item, select a heavier-weight enclosure material, or consider a different enclosure format. Paper folder stock and polyester film stock are available in a variety of weights and dimensions and there are numerous enclosure formats and designs to accommodate oversized materials, rolled storage, unusually fragile items, and items with special handling requirements.

For more information about enclosures and other storage options for paper-based materials, contact paper conservators at the Weissman Preservation Center.

Enclosures for Photographic Materials

The type of enclosure used for archival photographs can depend on how the collection is expected to be used.

Transparent plastic sleeves are helpful when a collection is likely to get frequent use as they can protect against handling damage. They are also useful for photographs with labels that are poorly adhered to the back of the prints. If the labels do become detached, the information will stay with the correct photograph. Appropriate plastics include polyethylene, polypropylene and polyester. Sleeves made of polyvinyl chloride are to be avoided as they can damage the photographs over time. For prints, look for sleeves that are welded on two adjacent sides, in the shape of an L.

The downsides to using plastic sleeves are the cost and the weight. For large collections these can be serious considerations. For some collections, plastic sleeves might only be used strategically on those photographs that are handling risks, such as those with tears or loose labels. Plastic sleeves have static charge so they are not to be used on photographs with flaking image layer or those with powdery hand-coloring or inscriptions. Plastic sleeves can cause rapid and irreversible damage to cellulose acetate and cellulose nitrate negatives so should not be used with those materials, unless used in cold storage.

Paper enclosures for photographs can be sleeves, meaning sealed on three sides, or folders. See section above (Protective Storage Guidelines for Paper-Based Materials) for more information. The enclosure should be made of ligin-free, acid-free, buffered (alkaline) paper stock and have passed the Photographic Activity Test, or P.A.T. The Photographic Activity Test confirms that the paper will not cause fading or staining of photographic materials over time. Suppliers of archival materials will usually indicate when enclosures, boxes and mat board are lignin-free and have passed the P.A.T. When using a paper sleeve, make sure that the image side of the print or negative is placed against the smooth side, and not the seam side, of the enclosure. This also has the important benefit of keeping the vulnerable image away from the abrasive edges of the seam. When choosing paper sleeves, look for enclosures that have two seams placed to the sides. Seams at the side, also called balanced seams, enable stacks of sleeved photographs to fit evenly in boxes.

For more information about enclosures and other storage options for photographs, contact photograph conservators at the Weissman Preservation Center.

Enclosures for Audiovisual Materials

Content for this section is under development.

For questions about enclosures for audiovisual materials, please contact the Weissman Preservation Center's Preservation Librarian for Audiovisual Materials.