GB333246A - Improvements relating to the electrolytic deposition of gold - Google Patents

Abstract

333,246. Grupe, W. F. May 3, 1929. Metal foil.-Gold leaf is made by electrodeposition on a metal strip of indefinite length; a carrier strip of non-metallic material is then applied to the gold surface by an adhesive releasable by impression transfer, and the cathode metal dissolved off. In the apparatus shown in Fig. 1 a band 12 of silver of thickness 0.001 inch connected as cathode at 18 is drawn from a drum 13 round a drum 14 of wood or hard rubber partially immersed in a gold-plating bath. A platinum anode 11 is supported beneath the drum 14 by an arm 26 which is oscillated by the rotation of the drum through a cam 27. Deposition on the edges of the silver strip is prevented by endless rubber bands passing over rollers 21, 22, 19<c>. 'The electrolyte is circulated to and from the tank 1. The plated strip 12<a> then passes through an alkali bath 15 and a water bath 16 and is dried by an electric heater 12<b>. It is then passed between pressure rollers 37, 38 together with a strip 36 of paper, glassine paper or cellophane, and the composite strip wound on a drum 40. The strip 36 is previously passed over a roller 33 fed from a heated bath 35 with heat-releasable material such as beeswax, rosin, or the substances sold under the registered Trade Marks "Cumar," " Bakelite," and " Duralite " and is cooled before joining the metal strip. The composite strip is then passed through a nitric acid bath shown in section in Fig. 4 to remove the silver. The strip 41 is passed between rollers 47 substantially at the liquid level. As shown, the paper carrier 41d is of greater width than the silver layer 41<a> and the extending edges are maintained above the bath by rods 48, 49, the lower face of the edges being protected by beeswax, rosin, or the like. The paper strip with the gold layer adhering is then passed through an alkali bath to remove acid, and though washing baths and dried. The gold surface may then be coated with shellac or or other sizing by a roller or by spraying and the strip again dried and wound. When the silver strip is of the same width as the paper the edges of both may be raised above the dissolving bath and subsequently removed by a slitting machine. Tn a modification the paper before application to the gold-plated strip is coated with an adhesive such as shellac at the edges only and these edges are cut off after removal of the silver leaving the gold leaf in the finished roll freely mounted between the paper convolutions.