The care of photographs. (Design Notes).

Starting with the invention of the daguerreotype in France in the late 1830s, photography has undergone a succession of technical innovations. Virtually all of them have in common a reliance on light as a catalyst for fixing the image on a surface that has been treated with chemical or natural substances. However, the very light that is necessary to create a photograph can also be its undoing. As Debra Hess Norris relates in a chapter about photographs in The Winterthur Guide to Caring for Your Collection, "Metallic silver, platinum metal, pigments, and, most recently, organic dyes are some of the materials that have been used to absorb and scatter light, thereby creating the images that we see. These final image materials are typically suspended and protected in a transparent binder layer. Commonly used binder materials include albumen (the white of hens' eggs), collodion (a form of cellulose nitrate), and gelatin (a highly purified protein commercially manufactured from animal hides and bones)."

To complicate the problem, photographs have over the years been printed on paper, glass, metal, cellulose nitrate, cellulose acetate, or polyester film, each to be conserved by somewhat different methods. All photographs are highly sensitive to light, and ...