Letterpress
A printing technique, in which the ink is printed on the substrate from a printing plate with printing elements raised above spacing elements.
Since printing is carried out under high pressure (15 kg/cm2), the prints have the following characteristic features:
- uneven ink distribution in the strokes: less in the middle than along the edges;
- a rim formed by the ink along the edges of a stroke (“beaded edges”) (fig. 1, a);
- substrate deformation (protuberance on the back side of the print (fig. 1, b); inward bulging on the front side of the print).
Letterpress printing is often used for printing serial numbers and bar-codes on the banknotes.
a
b
Fig. 1. Zoomed area of the image printed by letterpress. 100 Danish Kroner (2009):
a – front side of the print; b – showing paper deformation (protuberance) in the reverse side of the print