Improvements relating to etching processes

723,303. Etching. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Feb. 1, 1951 [Feb. 1, 1950], No. 2557/50. Class 100 (2). [Also in Group XL (a)] A method of etching includes the step of forming a resist on a surface to be etched by evaporating a non-metallic material and condensing the vapour thereof on said surface. The resulting resist coating is sufficiently non- porous even when thin. The resist material may be polythene, polystyrene, bitumen, colophony resin, or paraffin wax. A coating of metal, e.g. silver, platinum, gold or copper may be applied to the surface of a glass plate by condensation in a vacuum or by sputtering, and the resist layer applied over the metal, the metal coating imparting elasticity to the composite layer to prevent disruption. A further non-metallic coating may be applied under the metallic coating to increase the adhesion of the latter to the glass. In one way of carrying out the method, a glass plate to be etched is coated with non-metal by vaporizing the non-metal in a vacuum in an electrostatic field (see Group XL (a) ). After cutting the design, etching is carried out by hydrofluoric acid vapour.