GB191206115A - Improvements in or relating to Etching Processes. - Google Patents

Abstract

6115. Pilkington, H. M. March 11. Etching.-An etching process specially applicable for etching calico-printing cylinders consists in applying the design in an ink containing mineral fat, such as vaseline, applying an acid-resist consisting of a solution of dragon's blood in alcohol over the whole, treating with an oil solvent, such as petrol, which removes the ink and with it the overlying resist, and finally subjecting to etching-fluid. The design may be transferred to the cylinder from a flat plate as described in Specification 23,819/08 or through an offset roll as described in Specification 30,002/10. When the design comprises large areas to print solid colour, the etched areas are provided with ground lines, to retain the ink better, by printing lines, suitably from a plate, on the whole surface in an ink which is an acid-resist or is made a resist by sprinkling with bitumen or other resinous substance and warming, and then etching again. Another method of producing the ground lines consists in printing lines on the whole surface in an ink containing mineral fat, removing the resist by a solvent such as alcohol which does not attack the ink lying direct on the metal, applying resist again to the whole surface, removing the remaining ink lines together with the overlying resist by a solvent such as mineral oil, and again etching. In all cases where ink is removed by a solvent to expose the metal, the metal is preferably dusted over with a moistureabsorbing powder to remove traces of the solvent. The acid-resist is suitably applied to a cylinder carrying the design in ink by supporting the spindle at each end of the cylinder on a pair of rollers B and rotating the cylinder in a trough D containing the resist and mounted on pivoted arms E to permit of raising and lowering. The surplus resist is removed by passing a fine brush across the rotating cylinder or by a draining action as by mounting the cylinder at an inclination and lowering the trough gradaully or by filling the trough to submerge the cylinder and then drawing-off the resist. The rsist is hardened by heating the cylinder during or after drying. The solvent to remove the ink design and the overlying resist is suitably applied with cotton wool.