Etching Technique
This noble printing process is a symbiosis of classical etching and photography. Each print on the etching board is unique. The application of the oil ink, the rubbing out of the etching plate with gauze and the printing on the etching press are all done by hand for each print, just as with copperplate engravings.
I started my first experiments in photo-polymer intaglio printing after reading an article in a trade magazine about the New York photographer Peter Liepke, which aroused my curiosity. From his New York photographs, he first makes platinum/palladium prints or rubber prints, and then has a "Special Photogravure Edition" printed on the etching press.
As a photographer, I had already been working exclusively digitally for many years. However, I did not want to go back to the analogue darkroom with all the photochemistry. The classic heliogravure, in which a photographic template is etched into the copper plate using acid, was also out of the question for me. So I looked for a way to combine my photography with photogravure. In the process I came across the still very young technique of photo-polymer intaglio printing. It took 1 year and many many attempts until I was able to print the first intaglio print as I wanted it. I learned intaglio printing with copper plate, oil paint and etching press from the artist Sven Wohlgemuth in Hamburg.
The intagliotype etching technique is a "non-toxic intaglio printmaking": Instead of etching directly into the copper plate with toxic acid as in heliogravure, a thin photo-polymer layer is squeegeed onto the plate by hand in a darkened room with the help of a water sprayer. This layer is light-sensitive and still uncured. The remaining moisture between the copper plate and the polymer layer is pressed out in the etching press and the plate is then dried overnight in the dark. The next day, the printing plate is ready for exposure to the motif. The motif, which was previously printed on a transparent film with an inkjet printer and black pigment ink in the finest possible resolution, is then burned into the printing plate in direct contact under vacuum with UV light. Since the polymer only hardens when irradiated with UV light, the black pigment ink of the inkjet printer has the advantage that it does not let any light through. As a result, the polymer remains soft under every black pigment ink dot, no matter how fine, during exposure. Consequently, every tiny splash of black on the film from the inkjet printer causes a depression in the printing plate, and all the transparent areas on the film that let the UV light through harden the polymer layer. The image consists of many tiny depressions into which the oil ink is rubbed. To expose the plate, I use a 300kg contact copier from the analogue times of the Theimer company from the 1980s. This machine has a 1000 watt UV lamp and a heavy vacuum frame.
Before the gravure plate can be rubbed with oil ink, the soft unexposed polymer has to be removed from the plate. To do this, the exposed plate is briefly placed in a bowl of washing lye or washing soda. The alkaline soda dissolves the soft polymer out of the depressions. After a short intermediate rinse in water, the polymer layer with the depressions is fixed and hardened in an acidic vinegar bath.
