Precautions when printing gold ink and silver ink

2022-09-21
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Precautions when printing gold ink and silver ink

gold and silver powder are both coarse particles with poor transfer performance, which is very easy to stack. For stacking rubber and ink holding roller, relatively speaking, the stability of silver ink is better than that of gold ink. The solution based on film of decojet is better, and the printability is better than that of gold ink. However, both of them are not acid resistant, and are very easy to oxidize, resulting in ink discoloration. Because they have these characteristics compared with ordinary printing inks, they are prone to failure in the printing process. Therefore, the following points should be paid attention to when printing gold and silver ink

gold ink is a printing ink made of gold powder, which usually uses ground copper powder; Silver ink is a kind of printing ink made of silver powder, which is aluminum powder or silver paste after grinding. The fineness specification of gold and silver powder is expressed by "mesh". Generally, the gold powder is about 1000-1200 mesh; The silver powder is about 1000 mesh

1. Thoroughly clean the printing unit before putting it on the machine to ensure the purity of the ink

when cleaning, you can first clean it with yellow ink (gold ink) and white ink (silver ink) for 1-2 times, and then clean it with special ink cleaner. After cleaning, be sure to wait for the cleaning agent to evaporate completely before inking and printing. Because gold and silver inks will react when they encounter organic solvents such as car washing water, gasoline, kerosene, etc., causing ink discoloration

2. adjust the intermediate roller to separate it from the ink path and water path system

the intermediate roller is the ink roller connected with water on alcohoi (alcohol) wetting device (such as Heidelberg 102v), which is particularly helpful to establish the brand and international influence path and ink path. The main function of the intermediate roller is to transmit the fountain solution to the ink path system, so that the ink can be emulsified as necessary, so that the water ink balance can be achieved quickly before printing. Because gold and silver inks contain a large amount of copper powder and aluminum powder, and the particles are relatively coarse, they are not easy to dissolve in water and are not easy to be emulsified by water. Therefore, if the intermediate roller does not separate from the ink path and water path, the title of the article updated today is the working principle system of the digital universal experimental machine, which will inevitably produce many unnecessary problems, making the printing unable to proceed normally. For example, in the process of ink homogenization, the characteristics of the alcohol wetting system determine that the ink is transferred to the water roller through the intermediate roller, so that the water roller is covered with ink. However, because the metal ink cannot be emulsified, the water roller cannot absorb water, resulting in the water roller cannot supply water to the printing plate. Therefore, when printing gold and silver, the intermediate roller must be separated from the ink path and waterway system

3. try to arrange the gold and silver inks at the last printing

the viscosity of gold and silver inks is lower than that of four-color overprint inks. According to the principle of high to low ink viscosity of multi-color machine, in order to avoid the problems of color mixing, reverse overprint or poor overprint caused by wet press wet printing, it should be placed in the last group of printing

4. add desiccant

due to the poor fluidity of gold and silver inks, it is often necessary to add thin inking oil or debonding agent when using the machine to increase the leveling property of the ink. Add drying oil while adding additives. Gold ink can be added with about 1% red dry oil; The silver ink is generally added from kerosene and red dry oil, and the addition amount is about 1.5%; Or add mixed dry oil in silver ink, with the addition amount between 1% and 1.5%

5. Appropriately increase the alcohol content in the fountain solution

because alcohol is volatile, it can cool the ink roller; And the surface tension is low and the wettability is good, which is conducive to the control of moisture in the layout

6. the speed should not be too fast

the speed is generally controlled at 5000-6000 pieces/hour. If the vehicle speed is too fast, the friction between the ink rollers will be intensified and a large amount of heat will be generated, which will cause the ink to oxidize and change color

7. the acidity and alkalinity of paper cause discoloration

paper is often either acidic or alkaline. Especially for paper with large acidity, when printing gold and silver ink, on the one hand, it will cause ink discoloration, on the other hand, it will slow down the drying speed

8. The pH value of the hardware solution that will soon enter the flight can be appropriately increased

the pH value of the solution can be appropriately increased (reducing acidity), which is conducive to the printing of gold ink and silver ink, and the printed matter is not easy to fade

9. when making plates, we should consider the color stacking method

when overprinting gold or silver characters on the field color block, we need to make the place where the gold and silver characters are printed into hollow words, and the hollow words should be made smaller, and the gold and silver characters should be made larger; Or lay 40% flat on the hollowed out text, so that when gold and silver words are finally printed, all or most of the gold and silver ink can be printed on the blank paper to avoid printing on other ink layers, causing printing failure due to wet pressing. When overprinting text on a full plate of silver or gold, due to the strong hiding power of gold and silver ink, you can make hollow small characters on the gold and silver plates and make the first printed text thicker

10. correctly adjust the printing pressure

excessive printing pressure will accelerate friction and cause a large amount of ink to accumulate on the ink roller and blanket

11. The finished or semi-finished products after printing should not be stacked too much

on the one hand, because the ink film will adhere under the heavy pressure of the paper. On the other hand, gold and silver inks will release heat during the drying process, and the heat is not easy to dissipate in time under heavy pressure, which will accelerate the oxidation and discoloration of gold and silver inks

reprinted from: printed in China

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