Stamp gravure printing technology 1

Gravure stamps are printed using a dedicated gravure rotary press. There are four-color, five-color, six-color stamp printing machines, one-color engraving gravure printing, and five-color or four-color gravure printing. These special stamp presses are equipped with counting numbers, perforations, and cutting devices. Stamps can be counted, punched, and full-size stamps cut to size.
The ink used for gravure printing is a solvent-based liquid ink. When the printing plate is immersed in the ink fountain, the ink on the non-graphic part of the plate is scraped off by the squeegee, and the graphic part is the concave part of the printing plate. The ink is just stored. After being imprinted on the impression cylinder, this part of the ink is transferred to the paper. After multi-color overprinting, an exquisite stamp is transferred onto the paper.
The printing ink used for the engraved stamps is a viscous resin ink. Its ink transfer form is similar to that of the emboss, but since the graphic part of the engraving intaglio is concave, the non-graphic part (flat) ink on the plate is printed. It depends on a special wiping device to wipe off.
At present, there are roughly four types of ink wipes for engraving and printing: cloth wiper, trichloroethylene wiper, water wiper, and paper eraser. Rubbing the ink with a cloth, the three-dimensional impression and gloss of the printed ink layer are better, but the printing speed is slower; Trichloroethylene wiper printing speed is faster, but toxic, harmful to the human body; water wipe ink is a More advanced methods of wiping ink, but there are also problems of waste water treatment and pollution; paper wiping ink is suitable for small paper printing, and is not suitable for such large-volume stamp printing in China. China's engraving stamp printers are equipped with cloth rubbing devices.
In addition to the single photo ticket or the single carved ticket mentioned above, the intaglio stamp also includes a postage stamp that has been overprinted and embossed, known as the shadow carving stamp. It is a favorite of philatelists. The printing of shadow carving stamps overprints the combination of two different printing methods: gravure and engraving gravure.
Although engraving and gravure is an ideal process for printing valuable securities, it is difficult to express rich colors and delicate levels. Photogravure also has its disadvantages. Because some stamps have a darker color and require more ink for printing, gravure ink is a fluid with very low viscosity. Therefore, irregular watermarks often appear in deep-adjusted areas and the stamps are damaged. In addition, since the gravure printing patterns are all composed of dots of different depths and different sizes, zigzag slivers will appear at the edges of the thin lines or characters, which will affect the smoothness of printing.
In order to make stamps more perfect, the method of engraved intaglio and photogravure mixed overprinting is usually used to exert the respective advantages of the two printing methods so as to obtain more ideal printing effects, such as the famous “Landscape of Huangshan Mountain” and “Landscape of Mount Lushan”. The "Zodiac" stamps and "China Ancient Pagoda", "Lushan" and "Rare Bird" stamps issued in recent years have all been printed in this way.
Combining two different printing methods with different properties, the process is particularly difficult to overprint accuracy, their respective needs of the printing pressure is completely different, the ink properties are not the same, and there are different requirements for the printability of the paper Therefore, the mechanical error in printing is large, and the rejection rate is also higher than other printing methods. When designing the printing process of such stamps, it is necessary to fully understand and utilize the characteristics of these two printing methods, and to avoid weaknesses in order to obtain better printing results.
This type of overprinted version of the stamp is generally based on the engraving version, to make the screen pattern of the sketch effect, and then lined with the color of the gravure smudge. Therefore, the main lines and ideas of the engravings should be emphasized and real, and the contours and outlines of the motifs should be made. The inset color of the photogravure can be shallow and imaginary, supplemented by the detailed changes of colors and levels, so that even mechanical errors exist. It will not affect the clear and complete contours of the theme scenes. The printed stamp lines are solemn and straight, with prominent theme scenes, strong three-dimensional sense, and magnificent colors, with very unique artistic effects, especially worth collecting by stamp collectors.
At present, international stamps are mostly printed on engraving and offset printing. Modern offset printing technology greatly enhances the ability to express color and levels. Offset printing has clear and smooth text and lines, a uniform and thick background, elegant and harmonious pattern colors, and overprinting of engraving lines and ideas. The artistic effects of stamps are reflected. More perfect.
Stamps are very small printed materials, but the printing volume is very large. Not only do we need to arrange dozens or even hundreds of patterns on a printing plate, but it requires that the color and level of each pattern are completely consistent; and the same pattern of stamps should be printed repeatedly. Tens of millions of pieces, the printing cycle is sometimes several months. In this way, printing the same product for a long time and in large quantities also meets the very high quality requirements of stamp collectors and consumers. Not only must each overprint in the full-page stamp be accurate, but also the color of the face pattern printed in the front and post printing stamps. The level is the same.
This requires taking into account its characteristics during the pre-press process design to ensure that the print repeatability is better. For this reason, in addition to the use of conventional yellow, magenta, cyan, and black four-color inks, the application of spot color inks is also indispensable. According to the characteristics of the manuscript, different spot color inks are used for printing. The printed stamps can achieve satisfactory artistic effects and higher passing rates. Therefore, spot colors are often used in stamp printing. It is mainly used in the following areas: (to be continued)