Photogravure

Photogravure is the original method used to create photographic reproductions that combines the fields of photography and printmaking.  Photogravures are essentially photographs etched onto a copper plate and printed with ink.   

First, a positive transparency is made from an original photographic negative and is contact-printed under ultraviolet light onto a light-sensitive gelatin tissue.  Areas of the gelatin exposed to the light are hardened while less exposed areas remain unchanged.  This image-carrying tissue is then adhered to a copper plate and soaked in hot water.  Portions of the gelatin that received little light during the exposure to UV light are washed away, leaving only the hardened gelatin image.

The plate is then subjected to several etching baths where the chemicals migrate through the gelatin to etch the image into the plate creating grooves of varying depths.  Then the plate is inked and run through the press.  The deeper grooves hold more ink which create the darker areas of the image during printing.

The final result is a print that captures the richness of tone found in photographs.  This process was often used to reproduce paintings in the 19th century.

Serigraph

Serigraphy is a form of screen printing where a mesh is used to transfer ink onto an underlying layer, or substrate, except in areas covered by a stencil.  One color is printed at a time, so multiple screens may be used to produce one piece of multi-colored art.