Heliogravure
As photogravure (from Greek. Helios "sun"), also helioprint, photogravure, Photo Gravure, photogravure, photogravure, Klicotypie or solar pressure called, refers to a photographic Darkroom procedures . Heliogravure is the forerunner technique of modern gravure printing , with which photos and illustrations can be reproduced using a photomechanical printing process and with which real halftones can be represented. It is a further development of the aquatint process. The printing plate required for this is produced in a similar way to that for the aquatint etching .
history
The heliogravure was invented by Karl Klietsch (= Karel Klíč ) in 1879 .
"In 1884 [...] Johann Baptist Obernetter invented a new method of photo-engraving , which afforded the advantage of a real facsimile reproduction without retouching ."
Techniques of photogravure
A distinction is made between direct copy and pigment paper copy.
Direct copy
A copper plate is dusted with rosin or asphalt powder and this is melted by heating as a grid . A layer of gelatin is applied over this. This is sensitized (made light-sensitive) by bathing in a potassium or ammonium dichromate solution .
After exposure by way of contact copy by a semitone - slide the development takes place in warm water. The chrome gelatine hardens through exposure, while the unexposed parts remain washable. This creates a gelatin relief. Depending on the thickness of the relief, the acid can penetrate the gelatin. A thin layer allows it to penetrate quickly, which means that the copper is etched for a longer period of time and thus has deeper raster cells (= darker tone); with a thick layer, the acid cannot penetrate the plate or only penetrates it late, which means that it is hardly or not at all etched. When etching, depressions of different depths are created which, after washing off the gelatin layer, can absorb different amounts of color in accordance with the gelatin relief and allow differentiated halftone reproductions.
Pigment paper copy
In the case of pigment paper copies, the originals are exposed as an original- sized slide using the contact method on a light-sensitive chrome gelatine paper treated with potassium or ammonium dichromate, the so-called pigment paper . After exposure, the paper is soaked in cold water for a few minutes and pressed (clipped) onto a copper or steel plate that has been prepared using the aquatint process. For development, the paper and the unexposed areas of the gelatin layer are peeled off in warm water and rinsed away. A delicate gelatin relief remains on the plate. The artist can control and manipulate the subsequent etching in the ferric chloride bath. In the multi-bath process, several differently concentrated iron (III) chloride solutions are often used because the FeCl 3 tans the gelatin layer differently depending on the concentration and diffuses through to the copper plate to be etched at different speeds. Due to the different etching times controlled in this way and the rasterization through the aquatint grain, the plate can print halftones.
use
Today heliogravure is no longer used in industrial printing, but lives on in artistic gravure. However, it is used in the technical sense to preserve old graphics through reprints.
Hazard warning
Ammonium dichromate and potassium dichromate are toxic and carcinogenic chemicals.
See also
literature
- Wolfgang Autenrieth: New and old techniques of etching and fine printing - an alchemical workshop book for erasers: From "witch's flour and dragon's blood" to the photopolymer layer. Tips, tricks, instructions and recipes from five centuries . Krauchenwies 2010, ISBN 978-3-00-035619-3 ( excerpts online ).
- Josef Maria Eder : Detailed handbook of photography. Volume 4, part 3: Heliogravure and rotogravure printing, also photogalvanography, photoglypty, asphalt processes and photographic etching. 3rd, completely revised and enlarged edition. Knapp, Halle (Saale) 1922.
- Jaroslav Husnik, August Albert: The entire field of collotype printing and enamel photography (= chemical-technical library . Vol. 22). 5th, completely revised and supplemented edition. A. Hartleben, Vienna et al. 1922.
- David Morrish, Marlene MacCallum: Copper Plate Photogravure. Demystifying the process. Focal Press, Amsterdam et al. 2003, ISBN 0-240-80527-5 .
- Willi Schuldes, Horst Sprang: Heliogravure. Photography in artistic gravure (= library of design techniques ). Otto Maier, Ravensburg 1981, ISBN 3-473-61267-7 .
- From the senior of German photography (in other words : Hermann Krone ): The original photographic methods that remain of practical value for all time. Communicated with all recipes from my own practice in ancient times. = Original photographic methods. Reprint of the Dresden 1907 edition, edited by Irene Schmidt. VEB Fotokinoverlag, Leipzig 1985 (The "Dresden 1907 Edition" is a manuscript).
- Johan de Zoete: A Manual of Photogravure. A Comprehensive Working-Guide to the Fox Talbot Klíc Dustgrain Method. Joh. Enschede en Zonen Grafische Inrichting BV, Haarlem 1988, ISBN 90-70024-49-7 .
Web links
- Extensive collection of links on etching techniques and fine printing processes - here on heliogravure
- Etching online workshop book on the techniques of etching and the fine printing process
- Technique of heliogravure
Individual evidence
- ^ Meyers Großes Konversations-Lexikon , Volume 14, Leipzig 1908, p. 867; online via Zeno.org
- ↑ Compare the article by Erhard Schmidt at: pixeltrust.de