method for direct photomechanischen reproduction of naturobjekten, pictures and the like in natural colours, where only a single negative asphaltpositive and produced by farbselektionierung in printing plates for each farbtoene transform

摘要

344,148. Photo-mechanical printing- processes. ALIFREDI, G., 44, Via S. Chiara, Turin, Italy. Jan. 20, 1930, No. 1954. [Classes 97 (i) and 98 (ii).] In the preparation of colour printing plates, the object is photographed through a greenish-yellow coloured screen of pure rock crystal on to a panchromatic plate and a negative prepared therefrom, a number of impressions (depending on the colours in the object) are printed from the negative on to lithographic stones sensitized with benzol, Jew's pitch, lavender oil and aniline oil or chloroform, and colour selection is effected by removal of all parts of each impression other than those corresponding to the colour to be printed from that impression. The removal may be effected with solvents such as oil of turpentine, a mixture of oil of turpentine and benzol, or benzol alone. The prints may be transferred from the stones to zinc plates by means of ordinary transfer paper without ruled screens. Alternatively (1) each print is transferred to a transparent material (glass, celluloid, transparent paper) from which a carbon print is prepared and applied to a sheet of copper the latter being then etched or (2) each print is transferred directly on to copper which is then sprayed with isinglass and etched or (3) the impression stones are photographed and carbon printing effected as in the rotary photogravure method. The rock crystal used in taking the original negative is coloured with a mixture of aurantia naphthol blue and coreulein.