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Methods and processes used for printing postage stamps
Postage stamps show us that postal services are pre-payed. These small paper squares are attached to various mail, packages, envelopes, cards and aerogrammes. Their aim is to show that the sender has already paid the delivery of his card or letter, fully or partly.
Usually postal stamps are made from paper with the help of printing press. But in some countries there are different views on stamps making process. So, you can meet up with stamps made from such materials as wood, plastic, synthetics. The methods usually vary depending on the material that is used while creating this tiny item.
The process of postage stamps printing
It is interesting that stamps are printed by a great number of different processes. Every process possesses its own remarkable characteristics. Each epoch is famous for its own printing methods. Before 1970-s the stamps were mainly recess-printed from copper or steel plates. This process is known as intaglio. You can recognize intaglio stamps by slight ridges which appear because paper was forced under great pressure into the recesses of the plate.
One more process which is used in making stamps is letterpress, or relief-printing. Philatelists, who are really fond of collecting stamps and know a lot about the processes of making them, call such method typography. In this process design lines are raised on the plate. Then ink is rolled across the recess and later pressed into the special paper. Such stamps have a smooth surface but quite often you can see a design in the back.
Before 1934 cheap stamps in Great Britain were printed by letterpress method. Photogravure became popular at the same historical period. During this process the plate was photographically engraved. Here nice tone gradations were allowed. The images had fine lines that were created by the screening process.
Photogravure firstly appeared in Bavaria in 1914 and became particularly popular in1930s. Recently multicolor offset lithography has replaced photogravure. This modern process is cheaper and more reliable.
Printing methods in details
Stamps are printed differently, various processes and technics are used. The most popular ones are photogravure, letterpress, engraving, intaglio and offset lithography printing. Stamp printing machines also differ according to the stamp printing process.
As for intaglio, this is a printmaking method in which images are incised into a plate or matrix. The preferred surfaces for plates are usually steel or copper.
In this method the area for the image is recessed into the plate's surface. Later the recessed area is filled with ink. Then the images are engraved with the help of chemical tools.
Than the stamp makers feel the incision with ink, wipe extra ink with the help of tarlatan cloth. For ink to be transferred to the stamp paper high temperature and pressure are necessary. Gravure and engraving processes also use the intaglio process.
Line engraving stamps
Engraved images which are printed on stamp papers are called line engraving. The process is similar to relief or intaglio printing. Line engraving is made by carving into a plate. This plate can be made from steel or copper to which the ink is applied. After the stamp paper is placed over the plate, it is run through the rollers of the press.
Letterpress stamp printing
Letterpress is considered to be the oldest printing method. It was firstly used in 1840. It involves printing from a raised design, with the image being in relief on the plate.
While using this method you need to ink both reverse and raised surfaces, and then they are pressed into stamp paper to get a positive right-reading image.
Engraving stamp printing
Engraving stamp printing is the method where the ink is in a recess etched or cut into the surface of a printing plate.
The main characteristics of gravure stamp printing process are printing plates with recesses, or cells, on the surface. It is filled with ink as far as it passes through. You need to scrape the excess ink on the surface off by the doctor blade. Actually, some ink is finally left at the recess. While the plate rotates on the cylinder the stamp design is transferred to the paper or other materials, stamps are made from.
Every color of the stamp has personal printing unit. The main colors are yellow, black, magenta and cyan.
Modern methods of stamp engraving
As the time passed by the methods of stamp printing have generally changed. Nowadays electronic engraving is really popular. Using contemporary printing techniques professionals get high quality stamps with good resolutions. Lines and dots on these stamps are hardly seen, that can't be said about photogravure and lithography methods.
Lithography stamp printing
While using lithography method a stone or a metal plate are usually used. The first lithography stamps were made with water and oil. Contemporary techniques use chemicals for creating a certain image.
Lithography stamp printing consists of several processes. Firstly, the printing plate is attached to the printing press's cylinder. There are special dampening rollers which apply water, covering the blank portion of the plate. Hydrophobic ink is later applied to the ink rollers. It pushes the water away and adheres only to the emulsion of the image area.
Offset lithography is famous by creating a mirror image. So, the certain image is transferred to stamp paper exactly. The paper would be really wet in this case. The design of the stamp is applied to the printing plate with the help of chemicals, later on the ink is transferred to a secondary medium, for example, a rubber mat.
Due to its characteristics, this rubber mat manages to squeeze the water away and pick up the ink. Later it transfers this ink to the stamp paper with the help of uniform pressure. As far as the paper is rolling across the rubber mat, the images are appearing on the paper. This method got its name, offset lithography stamp printing, because the image of the stamp is firstly offset to the secondary medium.
Photogravure stamp printing
The method of photogravure stamp printing firstly appeared in 1830s. Actually it is an intaglio printmaking process where photographic images are printed with the help of mechanized etching plates.
In this method the design of the stamp is attached to the cylinder with the help of photographic process. Screening the image of a stamp is an important part of the process. Photogravure printing method boasts a number of tones and makes a number of cells that make up the perfect image.
Stamps printed with the help of photogravure possess a wide number of colors and tones. It happens because one can vary the depth of etch. In a stamp plate you can vary the quantity and depth of ink.
Postage stamp errors
During the printing process various errors can happen. Philatelists really appreciate them. Actually, such stamps are mostly collected because they are rare. The errors can be really different: errors in paper, design, invert, color or omission.