Photogravure is a method of printing high quality images using photographic and etching techniques.In the early 20th century, many superb prints were produced using photogravure printing. Photogravure printing was invented in 1879 and the basic process is to photographically transfer an image to a metal plate, etch the image on the plate then print from it. Photogravure and gravure prints have warm blacks and an amazing range of subtle gray shades.It is quite easy to identify a photogravure print. Look at the print with a good magnifying glass, and you will see a characteristic honeycomb appearance. This is caused by the grid used in the printing process. The image also appears soft and the dark areas seem pitted, as seen below.
Photogravure is rather a complex process with several variations, but the essence of it is as follows:
-Photographically transfer the image to a metal plate. This is done by coating a plate with light sensitive gelatin and then exposing it to the light from a photographic image (imagine shining a slide on it).
-The gelatin hardens most where most light falls, and remains softest where no light falls. So, if the gelatin is exposed to a negative photographic image, the darkest areas of the image will remain softest. These correspond with the lightest areas in the original photo.
It was this technique that enable the photographic image to be printed on the "normal" paper, as prior to its development they could only be printed on special photographic paper.
In the late 20th century the process went through something of a revival as computer and laser technology has driven down the cost of producing the metal printing plates. In fact, these machines have opened up many interesting, innovative uses for the process of photogravure, or photo etching as it sometimes called these days.