Photogravure on copperplate is a printing technique. The print is obtained by inking a copperplate containing an etched image and then transferring the ink onto a suitable paper passing through an etching press. The most important step is the method to transfer the image information onto the copperplate. The simplified method stages includes:
1) Digitization of the image if it is coming from a film camera.
2) Editing the digital image until its contents is aesthetically according to the author preferences.
3) Ink-jet printing the image life size and laterally reversed positive on a translucent media.
4) Sensitizing a gelatinized paper with potassium bichromate.
5) Exposing the sensitized paper through the positive image using a vacuum contact press an a suitable UV light source. This exposure creates a hardened gelatin layer whose thickness being proportional to the positive image transparency.
6) Reverse the exposed gelatinized paper onto a mirror finished copperplate. Then wash out the non hardened gelatin. Consequently, the hardened gelatin remains adhered to the copperplate surface.
7) Immerse the copperplate into an aqueous ferric chloride bath in order to etch the different tones. The acid progresses through the gelatin and reaches the copper quickly where the gelatin is thinner. Therefore, after a given etching time, the etching is deeper in shadows than in the image highlights. Thus the shadows will admit more ink in the printing step.
Digital image processing is a crucial phase to prepare suitable image version for Photogravure on Copperplate.
