Graphic printing gold and silver ink process experience
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Due to the different characteristics of gold and silver inks - general inks, in the printing process, if you do not properly grasp the technical essentials, it is difficult to guarantee the quality of the printed matter. Therefore, the characteristics of gold and silver powder (ink) must be known and mastered so that the printing efficiency and quality can be improved.
First, the hue, number and correct selection of gold powder
1, hue. Gold powder is alloy powder composed of copper, zinc and a small amount of aluminum. Its zinc content is between 8-12%, and the reddish color is called the red light gold powder; the gold powder with the zinc ratio of 20-30% is slightly colored. Green, it is called Qingguang gold powder; between the two is the blue and red light gold powder. Therefore, when printing, according to the original color requirements, a reasonable selection of various types of gold powder. If the original gold powder printing hue can not meet the original design requirements, then you can use the appropriate color of trace ink, add the gold powder ink and stir evenly, so that the gold powder to meet the hue requirements.
2, the number of heads. Because there is a difference in the thickness of gold powder, it is necessary to accurately select the gold powder of a certain number of meshes according to the printing characteristics. This is an important link for improving the printing quality and ergonomics. -- In general, the 800-grit gold powder is suitable for the letterpress printing process, and the fine-grained gold powder over 1000 mesh is suitable for the lithographic printing process.
Second, to improve the printing quality of gold and silver measures
1. Improve the Adhesion of Gold and Silver Printing Printing Inks Because the composition of gold and silver powder is metal powder, it is not sticky, and it can only be used after being mixed with appropriate amount of gold and silver oil to form a paste. If the gold and silver powder is adjusted too thick, it is not only unfavorable to the uniform transfer of the ink layer, but after the transfer to the paper surface, it is very easy to produce powder off the ink phenomenon, resulting in print quality accidents. To make the liquidity and printing and coloring power of gold and silver powder reach better printing quality requirements, except that the ratio of gold and silver powder to gold-plated silver oil is adjusted by 1:1, the gold and silver powders should be added separately in gold and silver ink. Traces of fast-drying bright yellow ink and white ink to increase the adhesion of gold and silver printing. In addition, the quality of pad printing technology can not be ignored. If the pad pressure is not uniform or insufficient, it is necessary to increase the thickness of the ink layer to meet the printing visual effect, so that once the printing ink layer is thicker, the adhesion is poor, and it is easy to remove ink from the powder. Therefore, the letterpress printing gold and silver powder, the edition should adopt the metal plate table with good flatness and high compressive strength, so that the printing pressure is even and solid, so as to better improve the adhesion of the gold and silver powder printing ink layer.
2. Measure to maintain a good print color of gold powder
As the chemical properties of gold powder are not stable enough, there will be different degrees of chemical changes when acid, alkali, carbonic acid gas and sulfide gas are encountered, which will reduce the gloss of the metal and even disappear. Usually the powder of gold powder in the moist air, under the influence of withered oil, its color will gradually turn dark brown and lose its original golden luster. Therefore, in the case of printing bulk products, it is not possible to adjust too many gold powder inks, and it is best to use three hours of gold powder ink that can be deployed at one time.
3, printing gold and silver powder (ink) on the quality of the roller
As the main component of ink transfer, the rubber roller plays an important role in the quality of the plate print. As the gold and silver ink metal powder particles are coarse, lack of stickiness and fluidity, and easy to condense and dry, the formation of poor ink transmission and ink, resulting in the production of paste plate defects. Therefore, the printing of gold and silver ink to use soft and full of good elasticity and sticky roller, while requiring the roller surface is smooth and no damage. To facilitate uniform ink transfer and layout ink. In addition, the contact between each ink roller, and the contact between the ink roller and the platen, should also be adjusted to a good degree of contact, so as to avoid the formation of ink deposits due to ink transfer and ink unevenness, and to cause stencil printing. When printing gold and silver ink, the number of rubber rollers used should also be reduced as much as possible to avoid the large coefficient of motion of the roller, rapid heat transfer, and long ink transfer cycle, so that the protective layer of gold powder, such as stearic acid, is destroyed. , resulting in oxidative discoloration of gold powder. If the continuous printing time is too long, and the gold-silver ink stays on the rubber roller for a long time, a dry ink film is formed, so that it is difficult to maintain a good transfer of the gold-silver ink, so that a paper pick-up occurs during printing. Increased viscosity and drying of inks cause barriers to normal printing. In this regard, the rollers should be cleaned first, and then the gold and silver inks should be properly increased in fluidity so that normal printing can continue.
Third, domestic gold and silver ink printing process essentials and experience
The use of original gold and silver ink printing, although not as good as the color effect of printing with gold and silver powder, but it has the main features of ease of use. The current gold and silver ink products are imported, domestically produced, and the brands are also diverse. The printability is also different. Some domestic gold and silver inks have poor coloring power and are prone to powder and bleaching quality accidents. This requires us to take a good grasp of the printing process technology. If the pad pressure should be uniform, the printing pressure should be sufficient to prevent the ink layer thickness from being increased due to insufficient plate pressure. In addition, if gold and silver inks are printed on the undercoat ink layer, gold and silver inks should be overprinted when the background color is not completely dry. In this way, the gold and silver ink can be infiltrated with the background ink, and the adhesion of the gold and silver ink is improved. In order to transfer the gold and silver ink to the paper surface more evenly, the printing speed must not be too fast. Especially for the field printing of gold and silver inks, the printing speed should be kept within 3,000 prints per hour, so that uniform and sufficient printing can be obtained. The printing pressure.
Gold and silver ink printing in addition to grasp the above essentials, but also pay attention to anti-sticking, which is important to quality control - the ring. The dry form of the factory-based gold and silver inks is oxidation-based. Gold and silver inks are not easily penetrated and absorbed into the paper fibers. To prevent the products from getting dirty on the bottom, the printed sheets should be placed in appropriate amounts as appropriate and allowed to dry before being stacked. . In short, printing gold and silver ink, as long as the effort to put a good operation and process technology, not only can improve the printing quality, but also - can greatly increase production efficiency.
Source: Printing World Kang Qilai