GB315257A - Improvements in or relating to photomechanical printing processes and to the production of maps and diagrams thereby - Google Patents

Abstract

315,257. Miller, O. M. July 10, 1928, [Convention date]. Drawings to Specification. Photo-mechanical printing-surfaces; reproducing maps.-Line drawings are reproduced so as to show, in addition to the lines, a series of graded half-tone tints, representing, in the case of maps, hypsometric tints. Convention line representation, e.g. contour lines, may be separately printed, and also a scale of numerical values adjacent specimen tint areas. Sectional half-tone printing-plates may be prepared for printing in different colours. For example, a hypsometric map may have altitudes printed in evenly graded hypsometric half-tone tints of one colour for one conventional representation, e.g. forests, other evenly graded half-tone tints of another colour for another conventional representation, e.g. cultivated land, and so on, and lines printed independently of the colours. A single printing-block for printing the half-tone tints of different areas is prepared by making a printer's copy of the line drawing, making therefrom an unreversed negative, and printing from this by a series of partial exposures, blocking out after each exposure a further area of the negative, and from the graded reproduction making a half-tone printing-block. Modified procedures are represented by diagrammatic drawings. For printing in colours, a series of printing-blocks may be obtained from the above half-tone negative of the required tints, and the parts of each plate not required for printing in any colour is " routed " or cut away. Printing- plates for coloured lines may similarly be prepared from a contour line negative.