This archive contains material relating to the photo-mechanical printing process invented by Walter Woodbury in 1865. Like the collotype process this also takes advantage of the changing nature of bichromated gelatine after exposure to light to produce a continuous tone print. Unlike the collotype process the bichromated gelatine layer does not form the printing plate.
A negative is placed upon a sheet of bichromated gelatine and exposed to a light source, the sheet is then washed to flush out the excess bichromate. Where the light has passed through the negative the gelatine is no longer absorbent but where the negative blocked the light the gelatine will accept the water and swell. After the sheet has been washed it will be seen to have a relief surface, raised in the areas that represent the dark areas in the finished print and flat in the areas that represent the light areas of the print. Once dried, the gelatine sheet is placed on a steel plate in a hydraulic press and a sheet of lead that is half an inch thick and half an inch larger than the layer of gelatine is placed on top. The whole is then placed under pressure, and the relief surface of the gelatine sheet is embossed into the lead.
The lead sheet produced forms the printing matrix used to make the print. It is placed face downwards in a press of Woodbury’s invention. A mixture of liquid gelatine and a colouring agent is then poured into the mould, a sheet of paper placed on the surface and the press closed. The press is then left for a few minutes allowing the liquid gelatine to set and adhere to the paper, which is then carefully lifted out of the press and placed in a drying rack. As the gelatine contracts slightly upon drying, causing the paper to curl inwards, these prints had to then be mounted.
The archive contains journal articles taken from contemporary photographic journals describing this process and its potential amateur and commercial use as well as describing further refinements to the process. Also included are detailed descriptions of how the process was carried out at two contemporary commercial studios as well as a photographically illustrated description of how the process can be adapted for use in the digital age.
This project was funded by an AHRC award for 'A digital archive of the nineteenth century Woodburytype and its working practice'
Hoskins, S., Thirkell, P., & Hill, V. Woodburytype database. [Dataset]