05-01-1933 дата публикации
Номер: GB385808A
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Принадлежит:
BELCOLOR GmbH
385,808. Photo-mechanical printing- surfaces. BELCOLOR GES., 31, Neuenburger Strasse, Berlin. March 31, 1932, No. 9260. Convention date, April 1, 1931. [Class 98 (ii).] A direct photographic full - tone copy is obtained from letterpress and/or block printing formes by covering by spraying the complete upper surface of the forme with a colour which is as actinically active or inert as possible, clearing the printing portion of the surface and coating the cleared surface by rolling thereon a colour having opposite actinic properties, and photographing. To obtain full contact, the developed negative may be treated by a known etching process. In an example, a bookprinting composition is sprayed with thin black pyroxylin, the printing parts are cleared and rolled with a good white paint. The prepared composition is either (1) photographed on to a film, through the support, the film being developed with pyrocatechin without sulphite and etched with warm water followed by further development or treatment with sodium sulphide; or (2) photographed on to bromide paper which is developed with a non-hardening developer, bleached with acidified peroxide of hydrogen solution, re-exposed and re-developed.
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