The Woodburytype process was developed by Walter Bentley Woodbury (b.1834, d.1885) based on a series of patents from 1864. The process sits between being photographic and photo-mechanical; it can be thought of as producing carbon prints mechanically, on an industrial scale. It is a continuous-tone process, no screen or ground is used.
A relief image, from a photographic negative, was produced in bichromated gelatine, this was placed in contact with a lead block and subjected to considerable pressure in an hydraulic press. The result was a lead mould varying in depth in proportion to the tonal areas of the original subject. Pigmented gelatin was placed in the mould and transferred to paper using a press. The Woodburytype produced a continuous tone image consisting of varying depths of gelatine, as no screen or ground was required the result was indistinguishable from a carbon print. The gelatine relief could be re-used to produce further lead moulds.
Woodburytypes were normally printed on thick paper or card, they could be produced in any colour but most often they were in a sepia tone that resembled a photograph, an extra coating of gelatine or similar was often applied to the finished print. Due to the pressure needed to create the mould the images tended to be small. Woodburytypes were most suitable for high-quality reproductions and were typically used for book illustrations, cartes de visite and also lantern slides. By the 1890s its use in book illustration was declining as processes such as photogravure proved more economic.
Woodbury introduced a related process called Stannotype. In this process the gelatine relief is not pressed into a lead block to produce the mould, thus the need for an hydraulic press was removed. The process starts with a positive transparency, from that a gelatine relief negative was produced, that was coated with a thin layer of india-rubber varnish. Tinfoil was laid over the gelatine relief and passed through a pair of rollers that pressed the tinfoil into the gelatine relief to produce the printing mould. Printing from the mould was the same as in the Woodburytype.
Woodbury continued to work on photo-mechanical printing including printing directly from the gelatine relief combined with a screen to reproduced half-tones. Disderi also patented a photo-mechanical process in 1867.
References & Notes
Tissandier, Gaston. History and Handbook of Photography. 1876. Gives a detailed account of how the process was used at the Goupil works in France, where it was known as Photoglyptie. Lon. Gaz. 23/3/1877, p. 2221.