The Library of Congress has nearly 150 million items in its collection, including at least 21 million books, 5 million maps, 12.5 million photos and 100,000 posters. The largest library in the world, it pioneers both preservation of the oldest artifacts and digitization of the most recent--so that all of it remains available to future generations.
I recently took a tour of two LoC departments that exemplify this mission: the Preservation Research and Testing Division in Washington, D.C., and the National Audio-Visual Conservation Center in Culpeper, Va.
The library's preservation specialists use the latest technology to study and scan ancient books, maps and other historical artifacts.
One process, called scanning electron microscopy, allows them to create elemental maps of manuscripts, identifying the chemical nature of inks and pigments, or the paper itself. Imperceptible changes made by artists appear plain as day when viewed using x-rays.