Patent GB-464333-A (GB)
Title: Improvements in or relating to the manufacture of gold leaf and like metallic films
IPC: C25D1/20
Filed: 1935-10-14
Abstract: 464,333. Foil. GRUPE, W. F. Oct. 14, 1935, No. 28328. [Class 83 (ii)] Metallic leaf is formed by depositing a metallic film on a supporting strip in a continuous length, varnishing the metallic film on the strip with a material such as shellac varnish, cellulose lacquer or wax, and then floating the strip across the liquid surface of a dissolving or melting bath with the support in contact with the liquid surface so that it is removed wholly or in part from the metallic film. A composite strip delivered from a roll 11, Fig. 1, comprises a silver backing with a thin gold coating on one side, which may be produced electrolytically as in Specification 211,539 or 211,540, [both in Class 83 (ii)], or by a cathodic emission process as in Specification 454,919, [Group XXXVI]. The strip, with the gold film on the under side, passes over a coating roller 15 in a bath 42 containing a size such as beeswax, Carnauba wax, shellac varnish, or a cellulosic lacquer, the size preferably being dissolved in a solvent of low boiling-point. The size is dried in an electrically heated chamber 18, and any residual solvent is driven off and the size baked or melted by an electrically heated roller 19. The strip may pass immediately through rolls 21, 22, or may be rolled at 20, and the rolled product. transferred to the position 20a and then delivered to the rolls 21, 22. The strip floats in dilute nitric acid in a bath 23 whereby the silver layer is dissolved. An inlet pipe 23a and an outlet pipe 23b maintain the strength and level of the acid. The strip is passed to a cleaning and neutralizing bath 26 containing water and ammonia, and to a final cleaning water-bath 30. A web 33 of tissue paper passes through a bath 32 containing a liquid such as petrol, benzene, xylol, acetone, chloroform, carbon tetrachloride, trichlorethylene, any of the paraffinic series of volatile liquids, including their chlorine derivatives, the higher alcohols and their derivatives, or low-boiling ethers, to prevent shrinkage in a subsequent drying process. The gold foil is led into contact with the unfinished side of the tissue paper, and the assembly passes through a hot-air drying-chamber 38 on conveyer chains 39, and is rolled at 41. Jewellers' rouge may be rubbed on the smooth side of the strip 33 before it enters the bath 32. The strip 41 may be cut into strips and put within a transfer book as described in Specifications 456,749 and 459,545, [Group XV]. A cellulosic backing may replace the silver strip. A band of the material sold under the Registered Trade Mark " Cellophane " having a superficial coating of a material which may be melted or dissolved, such as wax, is coated by cathodic emission, is sized as in the case of the silver backing, and is passed through a bath of hot water to melt the wax and enable the backing to be removed. Alternatively, a cellulose acetate or nitrate band after coating with metal and sizing, is passed through a bath 60 containing a solvent for the cellulosic base, the latter being wholly or in part removed. The strip passes through a hot-air drying hood 66, and is rolled at 68. The strip may pass from the bath 70, Fig. 4, of solvent over a conveyer 76 and into a water bath 79 which removes the solvent from the cellulosic material which is carried over on the strip, and causes the cellulosic material to precipitate in the form of a white, opaque coating. Tissue foil may be rolled with the foil so produced. Specification 333,246, [Class 83 (ii)], also is referred to.