Improvements in the Methods of Printing from Photo-engraved Intaglio Plates.

摘要

28,392. Swan, J. W., and Swan, D. Cameron-. Dec. 27. Litho,graphic and like printing.-Relates to a method of preparing and printing from photoengraved intaglio plates by the lithographic process, the plates described in Specification No. 21,018, A.D. 1902, [Abridgment Class Printing other than letterpress &c.], being specially suitable. The plate may be prepared as follows :-A sheet of lithographic zinc is coated with bichromated albumen, gum, gelatine, or other sensitized medium, dried and exposed under a half-tone positive made as described in the Specification quoted above. After exposure, it is rolled up with lithographic ink, developed in cold water, and gummed up. After drying, it is damped and rolled up with stiff lithographic ink and dusted with bitumen, dragon's blood, French chalk, or other powder. The plate is then etched with nitric acid, washed and dried, and cleaned with turpentine, leaving the plate in intaglio with the hollows clean zinc, and the surface retaining its albumen coating. Bitumen, resin, or other similar powder is dusted over the whole plate and the surplus wiped off, and the plate is heated just to melt the powder. The albumen is then removed in a bath of caustic potash and the clean zinc surface gummed up, and when the gum is dry the bitumen or other powder is dissolved out of the hollows by benzole, turpentine, or other solvent. Lithographic transfer ink is then dabbed into the clean hollows and the surface washed with gum and water. The plate is printed in a hand lithographic press or a machine having a flat or curved surface. The surface of the plate is kept clean by periodic damping with water or glycerine and water, or by similar methods. Instead of metal plates, stone may be employed.