GB606569A - Media for use in making camera copy and methods of preparing same - Google Patents

Abstract

606,569. Material for preparing drawings for photo-mechanical reproduction. SANDERS, L. S. July 30, 1946, No. 19506. [Class 98 (ii)] [Also in Group XV] Material for use in preparing drawings for photo-mechanical reproduction is made by printing on a base sheet of cellulose nitrate, cellulose acetate, ethyl cellulose or waterproofed paper, spaced parallel lines in which the lines are as wide as the spaces in between them, with white printing-ink or clear printing varnish; dusting the base with a chemicallydevelopable material such as lead sulphate in fine powder while the ink or varnish is still tacky; drying; sponging under a spray of water to remove unbonded developable material; drying; printing, with a similar printing plate to that first used, lines transversely or at right-angles to the lines first produced and with an ink containing another chemicallydevelopable material, such as mercurous chloride, which ink penetrates the dusted lines at the points of superimposition; drying, and again spraying with water to remove this ink from the places which it does not penetrate, to leave the base coated as shown in Fig. 3, in which alternate squares are coated with mercurous chloride, and with mercurous chloride, together with lead sulphate. The material may be given a surface coating, comprising starch and gelatin, to improve developer and ink-receptivity. The first developer may be aqueous thiourea, which produces colour in the mercurous chloride squares only as in Fig. 4, the second developer aqueous sodium sulphide, which makes both the mercurous chloride and lead sulphate visible, as in Fig. 5. In a modification, a gelatin coated paper sheet may first be printed with parallel lines of waterproof varnish or ink, dried, crossed with a line print of mercurous chloride ink which adheres to both the gelatin surface and the varnish, dried; immersed successively in aqueous lead acetate and sodium sulphate solutions to produce lead sulphate within the gelatin surface between the varnish lines; dried and treated with a solvent to remove the varnish and the superimposed mercurous chloride ink, to produce alternate squares of mercurous chloride and lead sulphate, of which the former may be developed alone to form a dot pattern as in Fig. 4, or both may be developed simultaneously to produce a result as in Fig. 5. In the modified method, other chemicals, also applied by double decomposition, such as cobaltous phosphate, nickelous phosphate, cupric tungstate, ferric phosphate or thalliumtungstate may be substituted for the lead sulphate, which substances will produce coloured precipitates with sodium sulphide. In either form of the invention a transparent base may be used. The material may be used in the production of plates for multicolour printing.