- gravure printing
Printing processes used for catalogs, magazines, newspaper supplements, cartons, floor and wall coverings, textiles, and plastics.The Bohemian Karel Klíč made photogravure a practical commercial process in 1878. An image is etched in the copper surface of the printing cylinder as pits or wells of different depths. In rotogravure printing, the cylinder rotates through a trough filled with fast-drying ink. A thin steel doctor blade removes the ink from the surface but not from the wells. The cylinder comes in contact with the paper, which draws the ink out of the wells. Because of the various depths of the wells, a full range of tonal values can be printed; in reproducing illustrations, gravure comes closest to simulating continuous-tone copy. In colour printing, a separate cylinder is prepared for each colour. See also letterpress printing; offset printing.
* * *▪ printingphotomechanical intaglio process in which the image to be printed consists of depressions or recesses on the surface of the printing plate. The process is the reverse of relief printing (letterpress printing), in which the image is raised from the surface of the plate. The printer forms the image by cutting into the plate by hand or by using acids or other chemicals to etch the plate along the lines of the desired image. The printer then covers the plate with ink and wipes the ink from the higher surface, leaving the depressions, or intaglio areas, filled with ink. Paper pressed to the plate then absorbs ink from the depressed areas. Varying the depth of the depressions provides tonal gradations in the printed image.In the photogravure or rotogravure (rotary photogravure (rotogravure printing)) process, a negative image is etched into the surface of a copper printing cylinder in tiny cells and dots of various sizes and various depths. These constitute the type characters and artwork with its tonal gradations. When the printing cylinder rotates on the press, ink is applied to it by roller, spray, or bath, and a flexible metal blade called a doctor blade removes excess ink, leaving the surface clean, with ink left only in the depressions. Paper is fed between the inked printing cylinder and an impression cylinder coated with a resilient blanket, which presses the paper against the printing cylinder. The intaglio areas then transfer ink to the paper.The gravure process requires careful preparation, but it produces good printing quality and colour, even on less expensive paper. The printing cylinder can be chromium-plated for durability in long runs and even replated if desired. Therefore, gravure is used for long runs of magazines and catalogs and colour supplements for newspapers. The process was originally developed for high-quality picture reproduction. It is also used to make art prints.
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