Patent GB-190811698-A (GB)
Title: Improvements in or relating to the Manufacture of Screens or Coloured Surfaces for Colour Photography.
Inventor: DUFAY LOUIS
Filed: 1908-05-29
Granted: 1909-02-18
Abstract: 11,698. Dufay, L. June 4,1907, [date applied for under Section 91 of Patents &c. Act, 1907]. Colour photography; screens.-Screens for tricolour work with contiguous colour elements in a homogeneous layer are produced by the successive application by imbibition on the surface of the screen of three colours. For the application of any particular colour, any parts to be coloured subsequently are protected by a greasy material, so that the part coloured may be protected by a varnish which will not dissolve or become incorporated with the ink but can be washed off with it from these uncoloured protected parts, leaving the coloured parts protected by the varnish. A bichromated gelatine surface is exposed behind a line or other pattern screen, washed and prepared, and then impregnated with a coloured aqueous solution of one of the three screen colours. It is then inked with a greasy substance, preferably of black colour. The greasy substance takes at the hardened parts of the gelatine, and the colour takes in the unexposed parts. Pulls are printed from this surface on to a gelatine film which is to form the screen or screen-plate, and result in an impression of colour interspaced with greasy substance. A colourless alcoholic varnish is now spread over, which will adhere on the colour parts but not on the greasy part. The surface is then treated with a solvent such as turpentine to remove all the greasy material and varnish thereon, leaving only the first colour impression component protected by the varnish layer. For the second colour the same process is repeated resulting in the two colours protected by a varnish layer, the varnish layer over the first colour preventing any ink or colour impression taking thereon. The printing, in obtaining the second colour, is done crossways to the first printing assuming the pattern is a line screen. The remaining uncoloured gelatine is coloured in the third colour by bringing the plate into contact with a thick layer of gelatine saturated with the third colour, which does not take where the gelatine is protected by the varnish over the parts already coloured. The varnish coating can now be removed leaving a homogeneous screen having contiguous coloured sections with a uniform depth of colouring throughout. According to the Specification in its original form as open to public inspection under Section 93 (3) (a), a dotted screen for the pattern in printing is obtained by means of a pulverizing- device or sprayer or by grains of resin or the like. The screens also can be utilized for photo proofs on paper visible by reflected light. Such screens are produced by slightly wearing away the network to give a reduction in the general intensity. They are prepared on films provided on one side with emulsion, and on the other side with the screen surface, and are temporarily secured to glass in order to be subsequently transferred to the paper or other print support. Further in lieu of using colours, and protecting these during the preparation of the screen by colourless varnishes, coloured varnishes could be used, which themselves constitute the coloured elements of the screen. Also for distributing the greasy protecting-material on the screen surface, any process of quick printing or spraying may be used, and the application of the greasy protecting material and of the colour may be done by successive manipulations.