The Woodburytype process is a photomechanical process invented by Walter Woodbury in 1864. It is technically not a photographic process as it does not involve light in the actual making of the print, but rather it is a type of relief achieved via printing press.
The process starts with a mold that was created using a photographic image. The mold is a sheet of lead etched with groves that represents the different tones of the original photograph. The George Eastman House explains it succinctly:
Lead as a soft metal is used to record the impression of chromated gelatin that becomes hard and insoluble when exposed to light. The gelatin layer is washed in warm water leaving a low relief of high points where light struck the plate, and low areas that can be washed away.
When pressed under extreme pressure against the lead, it leaves an impression like an intalio printing plate. Since it was made through a negative, when inked, the ink stays in the deep areas corresponding to the dark sections of the negative (the absence of exposure) and has progressively less ink where the hardened gelatin is raised and doesn’t take the ink, and from the negative are the light areas.
The ink is retained by another layer of gelatin that is pulled off and transferred to a paper support, which is a print recording the full tones of the original negative, and the lead can be used for multiple printings.
For a time, it has been the preferred method in producing illustrative material for books and other publications.
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