Intaglio printmaking is printing process in which paper is forced by a press into recessed areas on a metal plate, which hold ink. Contrary to intaglio is lithography, which reproduces the surface of the plate. The plate is made by an infinite variety of techniques. These range from the types of plates used (copper and zinc), to the acids used (nitric and ferric chloride), to dry point, aquatint, mezzotint, sugar lift, marbling and spit bite. Inking and printing the plate is just as diverse as there are innumerable choices of inks, colors, consistency, pressure, wiping, paper choices and overlaying techniques such as chine colle.
Photogravure combines these ancient techniques of intaglio printmaking with photo-techniques from the late 1800’s. It is a process highly revered in the early 1900’s as the finest way to reproduce a photograph. The process was used by any early photographers and was employed by Alfred Steiglitz in the days of Camera Works. Edward Curtis’ Native American Indian Portfolios were all reproduced in Gravure. The process today has become defunct because it necessitates knowledge of innumerable fields of craftsmanship, equipment, techniques, patience and time.
The process is an intaglio method of printing a copper incised plate in an etching press. A photographic positive film the size of the final image is exposed by high UV light source (carbon arc, metal halide or pulsed neon) in a vacuum frame onto a sensitized (potassium or ammonium dichromate) sheet of carbon tissue. The carbon tissue was originally prepared by coating paper evenly with egg whites. This thin tissue will harden in various densities depending upon the amount of light reaching its surface. A highlight area will be very dense and a shadow area will be very thin. An 18-gauge piece of copper is polished, filed and dusted with a very even coat of ground asphaltum in a dusting box. The plate is then heated and the asphaltum is melted on the copper with a hot plate. This dot pattern acts as a screen on the plate; all the dots are of even size. The exposed carbon tissue is then laid on top of the copper plate and placed in warm water. The warm water allows the paper backing to release and be removed from the plate. What is left is a very faint photographic gelatin image of varying thicknesses on top of the copper.
The copper plate is then bit in ferric chloride, an acid that eats away the exposed copper. The ferric chloride is made in 4-5 varying baumes. The more water in the acid, the quicker its bite, the lower the baume and the less contrast in the final image. As the acid bites it dissolves the copper in the shadow areas first and finishes in the highlights. A shadow area therefore will be bit more deeply and conversely a highlight area will be shallower. The shadow area, therefore, will hold more ink. In the final image all the dots are the same size, they either hold more or less ink: as opposed to half-tone where the dots are either larger or smaller.
After the plate is bit it is washed and prepared for printing. At this point the process resembles intaglio. The plate is heated, inked with a brayer, allowed to cool and hand wiped until the ink is removed from the surface. A great deal of choices is left to the printer as to how much ink to remove, as well as to ink stiffness or color. Etching paper is then soaked till it is soft and pliable, preferably an unsized paper, then it is blotted and prepared for printing. The plate is warmed and placed on the bed of the press. The etching paper is laid on top and three different wool blankets are laid on top of the paper. The plate is then pulled through the rollers of the press and the print is removed from the plate to dry.
The drying of the final print to flatten and absorb moisture is achieved by placing the print between blotter papers and changing every day with dry blotter paper. Heavy weights are placed on top of the prints to flatten. Deckled edges can be achieved either after the print has dried or before the printing process.
Positives are made on Lithographic film from Freestyle developed in Microdol-X for continuous tone. Positives can also be made on Pictorico film in a computer printer instead of preparation in the enlarger. There are an infinite amount of controls available through this medium. Carbon tissue is from Autotype and soaked in a 3 % solution of ammonium dichromate, squeegeed onto plexiglass and allowed to dry. Exposure is made with a mercury vapor light source in a vacuum frame. Ground asphaltum, from Graphic Chemical Co., is dusted in a hand made dusting box with a paddle to stir the asphaltum. Gravure screens up to 200 lpi and stochastic screens at 1600 dpi can be used instead of the ground asphaltum. The baumes of ferric chloride vary from 44% to 37%. My etching press is a hand-pull Sturgess Etching Press. I use a sizing catcher blanket, pusher blanket and cushion blanket. Printing papers are of a variety of manufactures, from Arches, German Etching, and Rives BFK. I prefer to use un-sized papers, as the binder or glue prevents the paper fibers from being soft and pliable. Chine Colle is all with 100% Chinese silk tissue.