A tintype, also known as a melainotype or ferrotype, is a photograph made by creating a direct positive on a thin sheet of iron coated with a dark lacquer or enamel and used as the support for the photographic emulsion. Tintypes enjoyed their widest use during the 1860s and 1870s, but lesser use of the medium persisted into the early 20th century and it has been revived as a novelty in the 21st.
Tintype portraits were at first usually made in a formal photographic studio, like daguerreotypes and other early types of photographs, but later they were most commonly made by photographers working in booths or the open air at fairs and carnivals, as well as by itinerant sidewalk photographers. Because the lacquered iron support (there is no actual tin used) was resilient and did not need drying, a tintype could be developed and fixed and handed to the customer only a few minutes after the picture had been taken.
The tintype’s immediate predecessor, the ambrotype, was the same process using a sheet of glass as the support. The glass was either of a dark color or provided with a black backing so that, as with a tintype, the underexposed negative image in the emulsion appeared as a positive. Tintypes were sturdy and did not require mounting in a protective hard case like ambrotypes and daguerreotypes. http://en.wikipedia.org/wiki/Tintype
Jules A. Martino