Organizing and Preserving Collections III
Part 3: Photo-Based Material

As with other archival materials, collections of photographs and negatives need to be organized to give context to each image and for easy item retrieval. If your photographs are already grouped according to subject matter, you can get right down to cataloguing them with registration numbers and housing them in appropriate enclosures. In this modern world of point and shoot, just because the shutter was pressed doesn't mean that the image is worth keeping, so it may be time to winnow your collections.

When dealing with a box of unorganized photographs, you must decide upon logical systems of order to define and categorize your collections. Family archives will benefit from chronological, geographical and event headings whereas items of an artistic or documentary nature would require different categories. The physical organization and storage of collections present unique challenges as photography encompasses a variety of materials. Photographic types run the gambit from daguerreotype to ink-jet prints, not to mention the range of negative substrates (glass, cellulose nitrate, cellulose acetate and polyester), which can have different optimum storage requirements and mechanisms of deterioration. Moreover, sizes and formats of early photographs can vary, and will not meet modern standard sizing.

Archival suppliers sell storage systems designed for specific sizes and material formats for glass negatives, cased photographs, carte de visite photos, slides, and the like. Depending on the types and sizes you have, standard storage systems may need to be modified to suit your collections. What follows are a few suggestions for the private collector to consider:

Size: If you only have a few non-standard sized photographs (such as cased photos, tin-types, or mounted photos) you might consider a custom mount which would allow for proper sequencing. An alternative would be to mark the place the photograph would have occupied in the collection with a note giving its storage location.

Materials: All photographs and negatives are sensitive to chemical deterioration. Contact materials should be PAT (Photo Activity Test) approved; archival suppliers carry storage materials with the proper specifications. Protein emulsions are thought to be sensitive to the high alkalinity of conventional buffered paper-based archival storage materials, so neutral pH cellulose, or archival quality plastic enclosures are good choices. For extra protection, Microchamber Silversafe boxes, papers and folders are double-sided: neutral pH for the contact side, and alkaline pH with volatile chemical absorbing zeolites for the non-contact side.

Temperature and Relative Humidity: To avoid deterioration temperatures should not exceed 21ºC, but lower is better. For mixed photographic collections, a relative humidity of 35-40% is best, and should never rise above 60%. Owners of valuable photographs should consider environmentally controlled cold or frozen storage.

Special Considerations: Cellulose nitrate and cellulose acetate negatives are often unstable. Cellulose nitrate may shrink, causing the gelatin emulsion to accordion wrinkle; cellulose acetate becomes brittle as it deteriorates, giving off a vinegar-like smell from released acetic acid. If your negatives show signs of these conditions, it would be best to have them copied, or put in cold storage to slow the process.

Photographic chemistry and conservation is extraordinarily complicated; for more information visit Wilhelm Imaging Research at: www.wilhelm-research.com.

by Rebecca Pavitt -

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Source: http://http://www.preview-art.com/Conservators/06-2011/conservation.html