The Photogravure process is a photomechanical photographic process in which
the finished prints are made in ink on a printing press.
Photogravure was developed in the 1850s. The process is rarely used today due
to the costs involved, but it produces prints which have the subtlety of a photograph
and the art quality of a lithograph.
The method, one of the finest ever developed, transferred the photographic
image to a copper printing plate, which was then etched to retain ink in areas
corresponding to the blacks of the picture (also see Woodbury-type process).
After taking a picture, a glass transparency is made from the negative.
A carbon print which has been exposed beneath the transparency is then transferred
to the plate. The plate is then bathed in warm water which causes the unexposed
gelatin of the carbon print to be washed away, leaving the image in relief.
Ferric chloride is then applied to the plate and etches into the copper.
The result is an etched copper plate of the original photographic image, which
then can be printed.
Read more about Photographic Processes