Finishing (pressure)

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In letterpress printing, finishing is the fine adjustment of the pressure force distribution in the printing machine. A distinction is made between the following types of finishing: First, the plate is adjusted, that is, the adaptation of the printing form itself. Then comes the compensating adjustment, so that the pressure force is balanced over the entire surface of the printing form. Finally there is the force adjustment, namely the adaptation of the pressure force to the printing form. In letterpress printing, the finishing is always applied in the elevator .

Panel finishing

Preparation of the printing forme: Necessary especially for clichés that have been nailed onto wooden sticks. In order to compensate for unevenness on the printing block, the substructure was adjusted.

Compensation dressing (pressure compensation)

Balancing of the pressure force over the entire printing area: In the grazing light, the relief of the slightly embossed print image on the back of the sheet shows whether the pressure force is evenly distributed over the entire printing area. The parts of the print image that do not print out enough are covered with paper in the elevator.

Power dressing

Adaptation of the printing force to the printing form: Flat parts of the image and bold, large fonts require a lot of pressure to print cleanly, while fine fonts and lines require less pressure. To compensate for the compressive force, those parts that require more compressive force are underlaid with tissue paper in the elevator . For this purpose, a print is first made on a sheet of paper (sheet of paper on which the sheet is attached) and the parts to be placed under are marked. Then, depending on the requirements, those parts that need more pressure are underlaid with one or more layers of tissue paper. This preparation sheet is then fitted precisely under the cover sheet in the elevator.

Since this type of finishing was very time-consuming, especially in multi-color picture printing, where each color requires its own finishing, other methods were later developed:

With mechanical chalk relief finishing (MKZ), a print is made on a carrier film coated with chalk. The chalk layer is then etched away. The oily printing ink protects the chalk layer when it is etched, which means that it is less eroded in dark areas of the image and a relief is created that corresponds exactly to the required pressure distribution.

With 3M dressing, a print is first made on a carrier film. Then you cover the printed film with fine resin powder. The deeper the tone, the more printing ink is applied, which can then bind more powder. The resulting relief is then fixed by heat.

literature

  • Laufer, Bernhard: Basic knowledge typesetting , printing, paper , Düsseldorf: Verlag Buchhandler heute, 1984. ISBN 3-920514-19-X
  • Scheper, Hans Jürgen: Examination knowledge printing technology . Itzehoe: Verlag Beruf und Schule, 2005. ISBN 3-88013-623-8
  • Wolfsturm, Hans-Jürgen and Burkhardt, Hermann: high pressure . Ravensburg: Ravensburger Buchverlag, 1994. ISBN 3-473-48382-6