A tintype is a monochrome direct positive on metal plate support. Like the ambrotype created on glass plate, it is a negative image that is seen as a positive, due to the dark support, the silver grains composing the light parts of the image. The resulting pictures are usually small formats, the most common being the "visiting card" (sixth or ninth plate), the "jewel - portrait" (2.5 × 3 × 3 cm) or the "postage stamp" (1.2 × 2.5 cm) formats. Full plate tintypes (16.2 × 21.6 cm) and landscapes views are the rarest.
The process was presented for the first time in France by Adolphe Martin in 1852, though many other patents were later filed in England and the United States. It is across the Atlantic that the tintype saw its greatest use principally from the Civil War period through the early twentieth century, under the term "melainotype" or "ferrotype". A quick and cheap process, it was popularized by itinerant photographers.
The manufacturing of a tintype is identical to that of Ambrotypes only the support differs, iron plate replacing the fragile glass plate.
A thin plate of tin about 0.15 mm thick is covered with a black varnish consisting of bitumen of Judea and carbon black, and insolubilized by light. It is then coated with collodion sensitized in a solution of silver nitrate. Afterexposure, the plate is developed and rinsed with water as soon as the image appears. The image is finally fixed, rinsed, and sometimes hand colored with light color pigments, before being varnished. In the twentieth century, the collodion layer was replaced by a gelatin-silver bromide emulsion.
Tintypes can be presented in paper mounts with rectangular or oval window mats to be slided conveniently into book-like albums, or more rarely protected in american cases, under glass. This type of presentation, commonly associated with daguerreotypes and ambrotypes, sometimes make them difficult to identify.When ferrotypes are not protected, they are recognizable by their metal support and alterations to its features such as deformation of the metal, or the appearance of rust between the support and the image, which can cause uprisings and scales. Images are often cream or chocolate-brown toned or colder when silver gelatin emulsion is used. The varnish may turn brown and crack due to exposure to light.
Visual glossary of photographic processes
© ARCP / Mairie de Paris, 2013.