(The following is a guest article about new preservation capabilities at the LOC by my colleague Donna Urschel, which was recently published in the the Library’s staff newsletter, the Gazette.)
For many decades, details of the 1791 Pierre L’Enfant Plan of Washington, D.C.—one of the many treasures at the Library of Congress—had been obscured. A long-ago application of a varnish preservative had darkened the map’s surface. But today, thanks to special imaging techniques, the invisible streets and special locations, including the “President’s House” and “Congress’ House,” pop out.
Hyperspectral imaging, a process of taking digital photos of an object using distinct portions of the light spectrum, is revealing what previously could not be seen by the human eye.
In room 27 on the sub-basement level of the James Madison Building, fascinating details of our historical heritage are coming to light in the recently opened Optical Properties Laboratory. Operated by the Library’s Preservation Research and Testing Division (PRTD) in the Preservation Directorate, the lab contains a hyperspectral imaging system, an environmental scanning electron microscope (ESEM), equipment for optical disc quality testing and a Fourier Transform Infrared Spectroscopy (FTIR) system.
The new lab enhances the Library’s capability to use nondestructive analytical techniques to track changes in optical properties of materials, helping conservators, curators and librarians extend the life of the collections. Along the way, many interesting details about the documents are revealed.
The Optical Properties Lab is one of three new labs in the Preservation Directorate. Two more will open in the Madison Building in 2010: the Chemical and Physical Properties laboratories. The new equipment and redesigned space will bring the 30-year-old science labs of the Preservation Directorate into the 21st century.