GB470385A - Improvements in processes for producing intaglio printing plates - Google Patents

Abstract

470,385. Photomechanical printing- surfaces. FEENY, V. F. (Miehle Printing Press & Manufacturing Co.) Feb. 24, 1936, No. 12175/35. [Class 98 (ii)] In a process for producing intaglio printing plates, a positive is made from a continuoustone negative through a half-tone screen spaced from the light sensitive surface at a distance such that minute light dots appear in the light areas on a ground glass screen used for focusing, this positive, in combination with letterpress if desired, is copied on a sensitized metal plate, and the plate is then etched to form ink wells of sufficient depth to allow for the spreading of the ink on the paper during printing. The dots in the areas corresponding to the whites of the original, in the positive may be removed by photographic reduction. In carrying out the process, the original negative is copied on a wet- or dry plate and may be combined with type matter formed by making a press proof of the matter, making a negative therefrom and copying this through a gravure or line screen to form a screened positive. The combined positives are then printed in a vacuum printing frame onto a copper plate coated with bichromated shellac, the borders or other areas to be protected from the etching agent being first painted with a solution of Syrian asphalt in turpentine. The plate is then etched with, e.g. ferric chloride and the resist removed by a cyanide or lye solution. Any necessary local re-etching may then be effected. The resulting plate has wells of uniform depth and of such size in the blacks that the ink spreads during printing giving solid black areas. The process may be used for preparing plates for printing in colours.