The task of preservation is to assure that our documentary heritage remains available for use over time without losing the information and essence that makes it important to our culture. The Library's strategy for preserving its vast collections reflects the diversity of its holdings. Every item in the collection has its own preservation needs, determined by its nature, condition, and intended use. Because library materials are primarily organic in nature, they will eventually deteriorate over time. Environmental control, appropriate housing and storage, and careful handling, all supported by a team of highly skilled conservators, constitute our first line of defense.
Sometimes, when materials are especially fragile, the Library takes special measures to ensure that the documents survive. Treasures such as the Rough Draft of the Declaration of Independence and the Library's two copies of the Gettysburg Address, written by Abraham Lincoln on inexpensive, acidic paper with inks that further corrode it, are in specially built environmental containers that have been purged by the inert gas argon to reduce oxygen and moisture to minimal levels. These cases prevent oxidation, including photo oxidation, and are covered with double ultraviolet light-filtering acrylic glazing to enable safe display under low-light conditions. These containers are in turn stored in a low-temperature vault that is maintained at a constant environmental level of 50 degrees Fahrenheit and 50 percent Relative Humidity. The vault has a fire-suppression system and is maintained under high security protocols.
Though these precious documents themselves are safe in their special housing and storage, people can still have access to them through the Library's Web site. Just as the digital age promises to make the Library's collections more widely available, the challenge to preserve the cultural heritage that the Library holds in trust for the American people continues to grow. As more and more of what the nation produces is stored on potentially unstable machine-readable media such as video and audio tape, the Library's world-renowned preservation research and development facilities are addressing these current challenges and anticipating those of the future.