Ambrotypes From the National Portrait Gallery October 31, 2012

In the mid-1850s American photographers, ranging from the celebrated Mathew Brady to the little-known itinerant L.W.F. Mark, embraced a new photographic medium known as the ambrotype. Taking its name from the Greek word ambrotos (meaning immortal or imperishable), an ambrotype was created when an underexposed collodion negative on glass was made to appear as a positive image by placing it against a dark backing. Drawn exclusively from the museum's collection, this exhibition includes ambrotypes of abolitionists Frederick Douglass and Anna Dickinson, as well as West Point classmates George Armstrong Custer and John Pelham, who later served as generals for opposing sides of the Civil War.