Digital Imaging Lab: Preservation

Negative Duplication

Many of the Library’s negatives are deteriorating. In 1991 a program was initiated to segregate glass, acetate, and nitrate negatives, and to duplicate negatives in areas of the Collection where deterioration had accelerated. More than 20,000 negatives were duplicated as full-size interpositives from which new, stable negatives were produced. Funding for these projects was provided by the National Endowment for the Humanities and the New York State Program for the Conservation and Preservation of Library Research Materials. Beginning in 2000, the process of duplicating negatives was replaced by digital capture.

Cleaning and Rehousing of Negatives

Glass plate, acetate, and nitrate negatives are cleaned before scanning. Dust is removed from the surface with an antistatic brush. The nonemulsion sides of the glass plate negatives are cleaned with a solution of ethyl alcohol and deionized water. All negatives are rehoused in acid-free, four-flap envelopes.

Cold Storage of Negatives and Film

After scanning, original negatives are stored in the Library’s walk-in freezer to slow their chemical deterioration. In preparation for cold storage, negatives are packed in acid-free boxes and sealed to keep out moisture.

Shelving negatives in the freezer

Digital Image Preservation

Images are captured as TIFF files at high resolutions that contain all recognizable information available from the original material. Metadata, recorded in the image’s header, tracks the image’s history including adjustments made in Adobe Photoshop. To safeguard digital image files from media failure or other catastrophic loss, multiple copies are made on different types of media. Files are stored separately on the image server (backed up on tape daily), 250 GB hard drives, and archival gold CDs. Digital files are cataloged with Cumulus digital asset management software.