Several methods are used for printing of stamps. Following are various term and processes used in the printing of Postage Stamps.
An engraver carves a needed design from a soft metal plate. This plate is called the ‘die’. The engraver carves the design backwards on the stamp die, so that when the design reaches the stamp paper, it will be forward. A proof is then made from the die. The design of the proof must be inspected and approved by postal authorities. Often, several proofs of the stamp die are made, each in a different color or combination of colors, in order that the postal authorities might select the best color or colors for the stamps to be produced. When the Plate has been approved, it is hardened and polished, and is then ready to be used to print sheets of stamps.
FLAT PLATE PRINTING:
In flat plate printing, the plate remains flat and ink is applied to the entire surface. Any surplus is wiped off. A sheet of stamp paper is then placed over the plate. A mat is positioned over this, and a heavy roller is run over the mat. The pressure of the roller forces the paper down into the engraved lines in the plate. These lines will receive ink and will be raised slightly above other portions of the stamps surface.
ROTARY PRESS PRINTING:
In rotary press printing two steel plates are curved into a circle. On one side of the plate is placed a roll of paper to remove excess ink from the plate. On the other side of the plate is placed the stamp paper that is to receive the design because the curving of the rotary plate ‘stretches’ the design, stamps printed by rotary press will be longer and wider in design than those printed by the flat plate process.
The principle used in typography is the opposite of that used in engraving. Areas around the design are cut away, rather than the design itself is cut away. The design remains at a raised level and the applied printing ink reaches only the raised area. Unlike engraved stamps, no raised lines and be easily seen or felt on the front of the finished stamp.
In lithographing stamps,the design is drawn on a lithograph stone with a special, oily ink. An acidic solution is then applied to the stone for a precise amount of time. The plate is then moistened, and the acid treated parpts of the plate will absorb water while the inked parts will repel the water. The plate is then inked, and only the oily area ink. A sheet of stamp paper is then pressed onto the plate and an impression is reveived. Lithography is advantageous in that many colors can precisely applied to the same stamp.
In offset printing, the stamp design are transferred from the steel printing plate onto a rubber blanket. The stamp paper is pressed onto the blanket, and the design is received from this rubber cylinder rather than from a steel plate. Offset is an extremely rapid method of printing, and is widely used today for the production of postage stamps.
Embossing has been used for the production of some envelopes and postcards. Some time this proccess is used to print stamps also. It involves impressing the back of paper with a design which will be raised on the front side.