Ambrotype: the "glass Daguerreotype"

The ambrotype is a variation of the wet collodion process, and was cheaper than the daguerreotype. The ambrotype was made by slightly underexposing a glass wet plate in the camera. The finished plate produced a negative image that appeared positive when backed with velvet, paper, metal or varnish, making it the 19th century equivalent of the "instant photograph".

The ambrotype and daguerreotype were almost always enclosed in a case as the fragile materials required protection.