Offset
A printing technique, which employs a plate with printing and spacing elements in the same plane. The inked image is transferred (or "offset") from the plate to a rubber blanket, then to the printing surface.
Traditional offset is based on the repulsion of oil and water, the image to be printed obtains ink from ink rollers, while the non-printing area attracts water, keeping the non-printing areas ink-free. The plates are dampened with water which adheres to the areas without images. The ink is added next, one color at a time, where it sticks to the areas with images.
Characteristic features of the prints:
- The substrate is not deformed;
- The paint strokes evenly distributed;
- The paint does not shine (fig. 1, a);
- The paper fibers can be seen through the strokes (fig. 1, b).
High offset is a method which combines letterpress and offset. The image is transferred to a rubber blanket from a plate with the printing elements raised above spacing elements. Printing pressure is lower than that in letterpress, and the plate does not contact the substrate, so there is no relief. The prints obtained by this method are characterized by more distinct boundaries than offset prints. Relief printing elements on a printed plate lead to the same boundary effects, as in letterpress, but it appears to a lesser extent.
a
b
Fig. 1. Offset Printing. 5 Yuan Renminbi (1980):
a – general view; b – zoomed fragment