The ambrotype or amphitype is a photograph that creates a positive image on a sheet of glass using the wet plate collodion process. In the United States, ambrotypes first came into use in the early 1850s. The wet plate collodion process was invented just a few years before that by Frederick Scott Archer, but ambrotypes used the plate image as a positive, instead of a negative. In 1854, James Ambrose Cutting of Boston took out several patents relating to the process and may be responsible for coining the term "ambrotype".
The ambrotype was much less expensive to produce than the daguerreotype, and it lacked the daguerreotype's shiny metallic surface, which some found unappealing. By the late 1850s, the ambrotype was overtaking the daguerreotype in popularity; by the mid-1860s, the ambrotype itself was supplanted by the tintype and other processes.
See also: Making the Positives: Ambrotype