daguerreotype
n.
A photograph made on a silver-coated copper plate and developed using fumes of mercury.
Notes
Invented by Louis Jacques Mandé Daguerre in the late 1830s and announced publicly in 1839, daguerreotypes were the first practical photographic process. They remained common until the popularization of the ambrotype in 1854. The surface is highly reflective. The image appears as a positive when viewed while reflecting a dark background and as a negative when reflecting a light background. The image is monochromatic, although color may have been added by hand. Unless special camera optics were used, the image is laterally reversed. The surface is fragile and may be tarnished. To protect the image, a daguerreotype is almost always mounted under glass with a paper seal around the edge; most daguerreotypes are mounted in a hinged case.
