Of the Mastery of Metal and Light
Dustgrain copperplate (photo) gravure or heliogravure is an intaglio etching technique first patented by William Fox Talbot in 1852 and further developed by Karl Klič in 1879. It is one of the few true continuous tone printing processes in which a photographic positive is exposed onto a sensitised gelatin tissue resist. The tissue is developed and adhered to a copper plate, dusted with fine rosin powder and etched in a series of carefully timed and controlled ferric chloride baths. The plates are then hand inked and printed in the same fashion as an etching plate. The prints display very finely rendered continuous tone, which is very difficult to achieve with traditional etching techniques.
photogravure /ˌfəʊtə(ʊ)ɡraˈvjʊə/
Process of engraving by photography
An image produced from photographic positive transferred to a metal plate and etched
Setting continuous tones into a surface using a continuous tone positive and aquatint
photo- from Greek, combined term for “light” and “to shine” (phos + bha)
-gravure from French grav(er), Germanic grave, Middle English graven, to engrave
William Fox Talbot makes two very important discoveries during his experiments in the 1840s.
1. Gelatin sensitised with potassium bichromate became insoluble when exposed to light and could be used as an etching resist.
2. Screen of black gauze or crepe could break up an image to provide the “shoulder” (grip or tooth) needed to print halftone or tonal images.
These discoveries not only lead to photogravure, but become the foundation principles of all photomechanical printing processes.