Close up of a photogravure print.
Steel faced photogravure plate.
Wiping the plate.
Wiping the plate.
Wiping the plate.
Printing.
The print and the plate on the press bed.
(Images from studios at John Goodman Photogravure).
Photogravure
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Photogravure is a complex etching process that involves working with photographic images.
Photogravure follows the concept that in order to print a photograph with black ink, a dot pattern must be created in order to show varying degrees of gray tones using the white of the paper. This concept is still used in the printing industry and is called a half tone and can easily seen in the photographs in a newspaper. Dots of varying sizes make up the tones we see in the photograph. Since photographic negatives start off as a continuous tone, the image must be converted in order to print it with ink. The dot pattern in a photogravure is the dot pattern created by a rosin aquatint on a highly polished copper plate. This creates a beautiful, very subtle quality to the photograph. The pattern is actually the random pattern of the dust settling on the plate.
A photosensitive gelatin is put on the plate after the aquatint. Then, a negative is exposed onto the gel. The plate is placed in a Ferric Chloride acid bath and the image is etched into the plate.
The printing process is different from other types of intaglio, notably the wiping and inking. The printing pressure is also much higher. Because of this, it is good to steel face the plate in order to preserve the image.