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.

Fenella France, a research chemist with the Preservation Research and Testing Division, uses a 39 megapixel camera to take high-resolution images of documents ranging from renaissance-era maps to American state papers.

"We don't filter at the camera, we illuminate with small wavelengths," Fenella said. "We're creating a reference set of samples. We can't take samples of the documents themselves--it's just not going to happen"

This technique creates a set of images like a 'stack of cards,' all identically framed but revealing a different spectral face of the subject.

The Gettysburg Address exists on her computer as 8 different documents, each representing a different waveband in the visible spectrum. But only some show the mysterious fingerprint residue that may be Lincoln's own.

"In the next 5-10 years, I wouldn't be surprised if they could pull residual genetic information from the documents. [This is why] one of our foci is making sure that we don't interfere with future research."

To read the complete article, see:Gallery: Digitizing the past and present at the Library of Congress(www.boingboing.net/2010/06/09/gallery-digitizing-t.html)