Still to be translated into German

Photogravure (source Wikipedia)


Photogravure Victor Hugo, 1883


The earliest forms of photogravure were developed in the 1830s by the original pioneers of photography itself, Henry Fox Talbot in England and Nicéphore Niépce in France. They were seeking a means to make prints that would not fade, by creating photographic images on plates that could then be etched. The etched plates could then be printed using a traditional printing press. These early images were among the first photographs, pre-dating daguerreotypes and the later wet-collodion photographic processes.
Photogravure in its mature form was developed in 1878 by Czech painter Karel Klíc, who built on Talbot's research. This process, the one still in use today, is called the Talbot-Klic process.
Because of its high quality and richness, photogravure was used for both original fine art prints[2] and for photo-reproduction of works from other media such as paintings. Photogravure is distinguished from rotogravure in that photogravure uses a flat copper plate etched rather deeply and printed by hand, while in rotogravure, as the name implies, a rotary cylinder is only lightly etched, and it is a factory printing process for newspapers, magazines, and packaging. In France the correct term for photogravure is héliogravure, while the French term photogravure refers to any photo-based etching technique.


Photogravure registers a wide variety of tones, through the transfer of etching ink from an etched copper plate to special dampened paper run through an etching press. The unique tonal range comes from photogravure's variable depth of etch, that is, the shadows are etched many times deeper than the highlights. Unlike half-tone processes which merely vary the size of dots, the actual quantity and depth of ink wells are varied in a photogravure plate and are often blended into a smooth tone by the printing process.  

A photogravure from 1901 by W. E. F. Britten for Alfred, Lord Tennyson's poem St. Simeon Stylites.


 Photogravure plates go through several distinct stages:

  1. First, a continuous tone film positive is made from the original photographic negative. A smaller negative can be enlarged onto a sheet of film, which is then processed to a range of continuous tones with specific densities.
  2. The second stage is to sensitize a sheet of pigmented gelatin tissue by immersion into a 3.5% solution of potassium dichromate for 3 minutes. Once dried against a Plexiglas (Perspex) surface, it is ready for the next stage.
  3. The third stage (usually the next day) is to expose the film positive to the sensitized gravure tissue. The positive is placed on top of the sensitized sheet of pigmented gelatin tissue. The sandwich is then exposed to ultraviolet (UV) light. A separate exposure to a very fine stochastic or hard-dot mezzotint screen is made, or alternatively an aquatint grain of asphaltum or rosin is applied and fused to the copperplate usually before the exposed gelatin tissue is adhered to the plate. The UV light travels through the positive and screen (if used) in succession, each time hardening the gelatin in proportion to the degree of light exposed to it.
  4. The fourth stage is to adhere the exposed tissue to the copper plate. The gelatin tissue is adhered or "laid down" onto the highly polished copper plate under a layer of cool water. It is squeezed into place and the excess water is wiped clear
  5. Once adhered, the fifth stage is to use a hot water bath to remove the paper backing and to wash away the softer, unexposed gelatin. The remaining depth of hardened gelatin is relative to the exposure. This layer of hardened gelatin forms a contoured resist on the copper plate. The resist is dried, and the edges and back of the copper are stopped out (staged).
  6. The sixth stage is to etch the plate in a series of ferric chloride baths, from the densest to slightly more dilute, in steps. The density of these baths is measured in degrees Baumé. The ferric chloride migrates through the gelatin, etching the shadows and blacks under the thinnest areas first. The etching progresses through the tonal scale from dark to light as the plate is moved to successively more dilute baths of ferric chloride. The image is etched onto the copperplate by the ferric chloride, creating a gravure plate with tiny "wells" of varying depth to hold ink. The pattern formed by the aquatint grain or the screen exposure creates minute "lands" around which the etching occurs, giving the copperplate the tooth to hold ink. The "wells" which hold the ink vary in depth, a unique aspect of photogravure.
  7. The final stage is to print the cleaned plate.