Ferrotype n. : A photographic picture taken on an iron plate by a collodion process; -- familiarly called tintype.

Example:
I am doing Ferrotypes (tintypes) in my 4x5 camera what can I use as a reversal developer on my b&w photos?

Taxonomy
tintype, photograph, ambrotype, plate, underexposed, free encyclopedia, photographers, ferrotype, melainotype, photographic emulsion, few minutes, backing, History, United States, metal plate, search, Presidential campaign, campaign button.

Defination from the web:
ferrotype, is a photograph made by creating a direct positive on a sheet of metal, usually iron or steel that is ... It was first called melainotype, and then ferrotype (by a rival manufacturer of the iron plates used); finally came the name tintype. ...