GB225015A - Improvements in the production of printing surfaces - Google Patents

Abstract

225,015. Hermann, C., and Horne, R. W. Oct. 10, 1923. Printing. - surfaces; etching.-An intaglio printing - surface, made from a plate or surface of metal or stone grained in the ordinary way and prepared by positive printing or transfer, is etched so that the depth of the etched areas a varies in accordance with the tone values, and the pits are surfaced with shellac or a similar resin which is insoluble in the fatty menstruum of the printing-ink or in acids and which adheres to the material of the plate and to the ink. The plate, after graining, exposing, and developing, is rolled up with a resist which is of the nature of printing-ink with the addition of a solvent or menstruum of low melting-point, such as vaseline, so that, on the application of heat during etching, the resist will melt and gradually spread over the unprotected areas and progressively stop the etching action. The heat may be applied externally either locally or generally as desired, or may result from the reaction between the plate and the etching acid. If etching is performed with nitric acid, gum is added in order to keep the etched cavities in a condition to take moisture and repel fatty ink. After etching, the resist is removed and the plate inked with fatty ink, a solution of shellac or other resin being then poured over the plate. The shellac, ink, and photographic film are then removed from the unetched areas c and these parts are treated to render them fat-repelling.