Improvements in the Manufacture of Plates for Printing in more than One Colour and in the Method and Apparatus for Colour Printing.

摘要

16,236. Hildyard, G. R. July 15. Overlays and make-ready arrangements. - In a process for printing in more than one colour, all the colours are printed in succession from one plate with the tones in relief by means of separate make-readies each having the parts in relief for printing its own colour. On the plate, which may be of zinc, the solids are first drawn in absoluteresist ink, and, after covering the plate with semiresist varnish, it is etched in dilute nitric acid so that the solids are left in relief. After being washed and dried, the nearest solid parts are painted with the absolute resist, semi-resist varnish again applied, and the etching repeated. This process is repeated until the lightest tones have been produced. The plate may also be prepared by a photographic process. A gelatine film on the plate is exposed under the negative just long enough to transfer the solids, when the soluble gelatine is dissolved and washed off, and the plate etched, the same process being repeated for all the successive tones. To get heavier tones, the plate may be painted at the required parts with a varnish or the like, such as gold size containing a little colouring-matter. A separate make-ready is prepared for each colour to be printed. The makeready is attached resiliently to the impression surface. The impression cylinder a has a suitable blanket b secured to one end of a sheet of flexible cardboard c, the other end of which is glued to a strip of stiff linen d, having elastic loops e attached to hooks on the cylinder axle. Cardboard layers c', c" are then used to build up the surface. To prepare the make-readies, the plate is covered with the first colour to be printed, an impression taken on the make-ready, and the parts not required to be printed in this colour cut out or removed by the operator so as not to print at these parts. Where the colour is to be lighter, the make-ready is slightly depressed. By repeating the process with the other colours, separate make-readies for each colour are obtained, but, when light and dark colours of a similar nature are to be printed, one make-ready can be used for them, the light colour being first printed, and then the parts not to be in the dark colour removed, so that they do not print in the succeeding impression. In preparing each makeready, it is preferred to take a pull or impression of the whole plate on a sheet of paper right over an impression of the colour or colours so far completed, so that the operator may see which parts are to be removed.