Ferrotypes (also known {in the USA} as Tintypes) are photographs made onto black-enamelled iron plates by the wet-collodion process. The black background made the transparent areas of the negative image appear black, and the dark, silvered areas were whitened using mercuric bichloride, and so appear light - in the same way as glass Ambrotypes.

French photographer Adolphe A Martin was the first to use this process, in 1853. A dry ferrotype processes later replaced the wet-plate system. As the process could be carried out inside the camera and needed no drying time, dry ferrotypes were popular with "while-you-wait" beach and street photographers[1]. Some cameras were advertised specifically for this purpose, such as the Mandel-ette.

Since the image must be viewed from the silvered side of (non-transparent!) plate, the image is left-right reversed (mirror-imaged) - a fault shared with most Daguerreotypes.

The process was used in the US until the early 1940s.

  1. Focal Encyclopedia of Photography, Focal Press, 1976 edition, p.588