Zincography
[[Category: Wikipedia: Redundancy March 2018 | zincography _-_ zinc etching ]]
As zincography , Zinkhochätzung or Chemigrafie a HW Eberhard 1804 is referred to in Magdeburg invented method using zinc plates instead of expensive, heavy lithographic stones . First the zinc plate was treated like a lithographic stone and used in the lithographic printing process in the lithographic press. From 1850 the method was used and further developed in the Barbizon School by Charles Emile Jacque and Karl Bodmer for illustrations in books and magazines. This technique was also known as Gravures en relief or procédé Compte .
Procedure
Since then, zincography has been improved and made usable for the letterpress press , with the printing areas being etched up. The printed image can either be drawn directly onto the polished plate with chemical ink or onto transfer paper and transferred, or it is printed and transferred onto transfer paper using letterpresses , lithographs and copperplate engravings . Another option is transmission using photography , a process known as photo zincography .
The transfer is done using a special transfer paper on the zinc plate, which has a soluble layer that adheres to the metal together with the printing ink. The print image is reinforced by the coating with a solution of gum arabic and diluted paint. The dried plate is then dusted with a fine powder made from a mixture of wax , colophony and asphalt , which is allowed to melt under gentle heat, while larger non-image areas and the entire back are coated with a solution of shellac and alcohol.
For etching, the plate is placed in a flat wooden vessel filled with pitch, which is about 2 cm high filled with a mixture of 40 parts of rainwater and 1 part of pure nitric acid . After about 2 minutes, the plate is rinsed in pure water and dried. Then the resin powder is melted again in such a way that it flows down slightly with the color of the drawing on the lines. The chemigraf now applies a mixture of letterpress and lithographic ink, to which a little resin and wax is added, with a leather roller. The plate is then placed in the etching water again and the etching process is repeated up to six times with reinforcement and, if necessary, renewal of the etching liquid.
After the sixth etching, the paint is washed off with turpentine and a sharp brush, the plate is placed in a hot potash solution and dried. Larger areas that should appear white after printing are chiseled or sawn out, followed by etching.
Chloric acid used for etching produces beautiful, shiny surfaces and clean, sharp lines. Although it has been possible to bring the zincographic etchings to a high quality standard, they can only replace the woodcut where the artistic perfection of the production is less important than the speed of the creation of illustrations or accurate facsimile . A further development of zincography is called electrochemistry .
Chemigraphy
Modern zincography is known as chemigraphy. Until about 1956, this procedure was carried out as follows:
First the repro photographer cleaned a pane of glass thoroughly and provided it with a primer. This primer consisted of a solution of mineral spirits or mineral spirits with an adhesive. The mixture was poured onto the glass plate and dried. Usually several plates were prepared as a supply for a working day.
The photographer then coated the glass plate with a liquid, light-sensitive collodion preparation and placed the wet photo plate in a cassette that was hung in the repro camera. The approximately 10-minute exposure was carried out with 4 carbon arc lamps .
After the plate had been developed, fixed, washed and dried, a photographic negative of the printed image was obtained. In the meantime, a 1.5 mm thick zinc plate of the appropriate size has been degreased and given a light-sensitive layer. Their sensitivity to light was so low that the chemograph could work in yellow light. The photographic negative was placed with the layer side on the light-sensitive zinc plate in a copy frame and pressed on under vacuum . The exposure was also carried out with carbon arc light. The exposed areas of the image hardened while the unexposed areas were rinsed off with water, so that a positive printed image appeared on the zinc plate. The printed image was made acid-resistant by heating the plate to approx. 300 degrees Celsius .
The first etching took place in highly diluted nitric acid in an etched bowl made of stone or plastic and removed approx. 0.1 mm of the zinc plate. Mechanical etching machines were used until the 1980s. The bath (emulsion) of nitric acid and side protection agent contained therein was thrown over paddle wheels onto the rotating zinc plate on the closed lid. Non-printing areas were about 0.5 mm deep. Larger non-printing areas were also placed deeper in the milling shop. (This also saved the early saturation of the acid bath) Each zinc plate consisted of several, loosely arranged subjects, which were then separated with clippers. Depending on the amount of metal that was etched out, sooner or later the acid bath was saturated and had to be drained. In earlier times it was simply diluted into the sewer system, at the latest in the 80s it was collected in its own containers in the cliché establishments, then neutralized with caustic soda and drained into the sewer system.
Today, chemigraphy still plays a role in the production of embossing clichés for blind embossing or leather embossing. Magnesium clichés are used here.
After completing the cliché , a proof was made for checking.
Well-known chemographers
literature
- Motteroz: Essai sur les gravures chimiques en relief , Paris, 1871
- Jacob Husnik: The zinc etching , Vienna, 1885
- Rudolf von Scherer: Textbook of Chemigraphy and related subjects z. Gebr. F. Book printer, lithographer, photographer , Vienna, 1877
- Wilhelm F. Toifel: Handbuch der Chemigraphie , Vienna, 1882
- Krüger, Die Zinkogravure , 2nd edition, Vienna 1884
- Volkmer, The Technique of Reproduction , Vienna, 1885
- JO Mörch, Handbuch der Chemigraphie und Photochemigraphie , Düsseldorf, 1885
- Josef von Böck, Die Zinkographie in der Buchdruckerkunst , Leipzig, 1885
- Chemigraphie , 8th, rework. Aufl., 1966, Handbuch der Reproduktionstechnik; 2.
- Eduard Schmid: Aluminum graphics and zincography: lithography with a difference ; (a technical guide to new creative planographic printing techniques), Eitorf, Gerstäcker, approx. 1999. ISBN 3-00-000029-1