“Daguerreotype: A product of the first widely used photographic process (1839 onward), named after its inventor, L.J.M. Daguerre. A daguerreotype is made without a negative by exposing a silver halide coated copper plate and then fuming it with mercury vapor to bring out the image, which characteristically appears in reverse. More popular than the contemporary calotype process, the daguerreotype was gradually supplanted after 1851 by the collodion wet plate process.”
Excerpted from: Diamond, David G. The Bulfinch Pocket Dictionary of Art Terms. Boston: Little Brown, 1992.