Tintype: There is No Tin in a Tintype

A wet-plate collodion process produced on a thin iron plate--named the melainotype (melaino, meaning dark or black) or ferrotype (ferro, referring to iron) and popularly called the tintype--was developed in Ohio in the early 1850s. While many mid-nineteenth century photographers did not value the tintype, it held many advantages over earlier photographic processes. It was less expensive, easier and faster to produce than the silver-plated daguerreotype, and much more durable than the glass-plated ambrotype. Like the ambrotype, the tintype was simply a collodion negative image that appeared as a positive due to the black (japanned) base upon which it rested. Despite reaching the peak of its popularity during the Civil War, the tintype continued to be used well into the second quarter of the twentieth century.

Patent number 14,300, "For the Use of Japanned Metallic Plates in Photography," was issued on 19 February 1856 to Professor Hamilton L. Smith of Kenyon College, Ohio. The patent illustrated "the obtaining of positive impressions upon a japanned surface previously prepared upon an iron or other metallic or mineral sheet or plate by means of collodion and a solution of a salt of silver." Additionally, the patent offered a description for preparation of the iron plates and presented the formula for japan varnish, its application, and baking. The six basic steps involved in the tintype process were: coating, sensitizing, exposing, developing, fixing, and washing the metallic plate.

Unlike the daguerreotypist who had to buff and polish silvered plates in order to produce his image and the ambrotypist who had to carefully clean and polish his glass plates, the tintypist merely had to dust off his previously prepared japanned plate with a cloth in order to ready it for coating. A highly toxic and inflammable collodion solution of pyroxyline (nitrocellulose commonly called guncotton), alcohol, and ether was applied to the thin enameled (japanned) black iron plate immediate prior to exposure. Preparation of collodion was often a matter of experimentation: the solution had to be translucent and free of floating particles and at the same time thick enough to create a coating on the iron plate. Because photographic collodion was fast-drying, additional trial and error taught the operator the point at which the solution would cover the plate without waves or ridges.

After the collodion had semi-hardened to a tacky surface, the plate was sensitized in an "exciting" bath consisting of silver nitrate, potassium iodide, nitric acid, and distilled water. The plate was lifted from the bath carefully (splashing of excess silver nitrate caused dark spots to emerge on the finished image) and allowed to drain briefly before being placed in a covered plate holder, known as a photographic frame.

Once the subject was set, the photographer needed to place the wet, sensitized plate in the camera, lift the plate holder's cover, remove the lens cap, and determine the correct timing for the exposure. By 1872 exposure time for the tintype, highly dependent on the amount of available light, varied between three and twenty seconds. After the lens was capped, the exposed plate was closed off in the photographic frame, removed from the camera, and returned to the darkroom for the next stage of the process--development.

The developing solution was a mixture of water, ferrous sulfate, and glacial acid. In the darkroom the operator removed the plate from the photographic frame, placed the plate, collodion side up, in a tray containing the developing solution, and rocked it gently to prevent uneven processing. After development, the plate was immediately and thoroughly washed with water and deposited in a tray of fixing solution that made the image permanent by removing the unexposed silver. Another highly toxic chemical solution, potassium cyanide, was used for the final fixing step. The plate was then dried and often coated with varnish to preserve the image.

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