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The
Photogravure Printing Process
What
is a Photogravure?
A
photogravure is a photographic image produced from an engraving plate. 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. In
essence, the production of a photogravure consists of three steps: taking the
picture; producing a printing plate of the image; and printing the image on
paper.
The
basic process, also called photogravure, was developed in the 1850s. After
taking a picture, a glass transparency is made from the negative. Next, a copper
engraving plate is dusted with grains of bitumen and heated so that the bitumen
becomes attached to the plate. 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
eats into the copper in proportion to the highlights and shadows of the gelatin
relief. The result is an etched copper plate of the original photographic image.
The
final step, printing, involves spreading ink evenly across the plate and then
pressing the plate onto the paper. The combination of the chemical and
mechanical process produces an image both warm and precise. A photogravure looks
like a photograph but is a series of connected lines, rather than unconnected
dots as in a photograph. The rich sepia ink and handmade paper used for the
Curtis photogravures are the final elements in the production of the beautiful
art prints of the North American Indian.
Return
to Edward S. Curtis Collections
Source:
The Curtis Collection www.curtis-collection.com
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