GB447045A - Improvements relating to the preparation of printing surfaces for colour printing - Google Patents

Abstract

447,045. Photomechanical printing- surfaces. YELLAND, N. W., Capesthorne, Wythenshaw Road, Northenden, Cheshire. Aug. 13, 1934, No. 23351. [Class 98 (ii)] To provide the necessary allowance between the colour areas on engraved surfaces for multicolour printing, a negative is prepared having the boundary line round each area in intaglio or relief and these lines are projected onto a sensitive surface spaced from the negative so that an image is produced with a double border line. An image or ground may be enclosed within each boundary line on the negative, for example, by exposing a plate bearing an image of the ground under an engraver's sketch, or a positive copy thereof, bearing the boundary lines, and developing as a wash-out relief so as to remove the ground in the unexposed areas. Or, a plate bearing an image of the ground may be exposed for a sufficient time to destroy the ground under the transparent lines. The thickness of the double line produced may be varied by varying the distance between the negative and the sensitive surface or by altering the size of the boundary lines on the negative. It may also be varied by employing a different thickness for the sensitive material which may be of gelatine sensitized with a bichromate. The ground may be produced by mechanical or photographic means, e.g. by exposure through a screen. To still further increase the allowance, a positive having broader lines may be made from a negative of the original using a ring of lamps as a light source, and employed as the original as described.