Several issues to be aware of when printing gold ink
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Gold can give people a gorgeous and noble feeling, and the golden color of the golden light is also unable to express the spectral color. Therefore, gold ink printing is widely used in packaging and printing technology, and plays a better role in improving the image of goods. However, since the main raw material of gold ink is brass powder, it is chemically active metal, which is prone to discoloration. Therefore, we should pay attention to the following situations when printing gold ink:
1 Gold ink is easy to contact with air and water vapor and chemical reaction causes discoloration. Therefore, it is necessary to do a good job in the storage of gold powder, and not let it be exposed to the air casually. The unused gold powder should be tightly covered;
2 Because the chemical nature of the gold powder is not stable enough, if it is in contact with acid, alkali, carbon and sulfide, different degrees of chemical changes will occur. The metallic luster is reduced and the gold ink is blackened. Moreover, gold ink should be avoided for printing large-scale domestic coated paper and offset paper, because the paper produced by the acid papermaking process is acidic, and the gold ink not only discolors after printing, but also loses luster;
3 Auxiliary materials for metal inks should not be used, and acid-containing auxiliary materials should not be used, but neutral substances should be used;
4 The use of gold ink should be mastered with the principle of printing with the tone, that is, the amount of one-time adjustment should be suitable for continuous printing for about 3 hours, so as to avoid excessive adjustment of the gold powder in the grease for too long, contact with air to oxidize and deteriorate and lose golden luster. ;
5 The speed of gold ink printing should not be too fast, because the frictional heat of the ink roller is increased accordingly, so that the gold ink is easily oxidized and blackened. Therefore, the speed of the printing gold should be controlled at about 3000 sheets/h;
6 The offset printing solution of offset printing gold should use a dampening solution containing acid or gum to avoid the reaction of the acid dampening solution and the gold powder, so that the ink color of the printing product becomes dark and tarnished;
7 When printing gold, the rubber roller should be adjusted. The position of each rubber roller should be adjusted accurately to avoid the occurrence of ink accumulation during the printing process due to poor ink transfer, so that the gold powder stays on the rubber roller for a long time, causing the oxidative discoloration of the gold ink. ;
8 The semi-finished products of printing gold ink should not be stacked too much, otherwise the heat released by the gold ink during the drying process of the paper can not be emitted as soon as possible, and the gold ink will also be oxidized and discolored;
9 When the machine ink fountain and the ink roller are cleaned with kerosene and gasoline, the organic solvent retained on the surface has not completely evaporated, that is, the gold ink is printed immediately, so that the gold ink reacts with the solvent to cause discoloration;
10 If you print gold on the ground color, you should pay attention to the appropriate addition of dry oil in the background color, so as to avoid overprinting the gold ink because the bottom ink is not dry, it will affect the luster color of the gold ink.
In summary, there are many reasons for the discoloration of gold ink. As long as we correctly understand and master the characteristics and printing suitability of gold ink, adopting reasonable and scientific process measures can not only effectively prevent discoloration of gold ink, but also better Improve the quality of gold.