Brief analysis and precautions of the hottest gold

Brief analysis of gold ink printing process and precautions

release date: Source: China paper industry

in commodity packaging and label printing, gold ink is often used to realize the printing of gold graphics and texts, which can give people a feeling of delicacy, magnificence and nobility. As a special printing method, gold ink printing is different from ordinary ink printing in the use of printing raw materials and process operation. Today, China's paper industry will start with printing and analyze the relevant contents in detail

1. Golden ink blending

golden ink is made by mixing gold powder, gold blending oil and a small amount of auxiliary materials. Ordinary color inks are pasted and stored in cans. Usually, gold ink is stored in two different containers with gold powder and gold transfer oil. When printing gold ink, the gold ink is mixed according to the proportion (usually the ratio of gold powder and gold transfer oil is 1:1). At present, there are also deployed gold ink supplies on the market, which can be printed directly. However, printing plants should consider factors such as the amount of ink used in the layout, the printing cycle and the number of products. Because the printing performance of gold ink will change and lose its original metallic luster after it is turned on for 1 ~ 2 hours, it is best to use gold ink when printing

2. Gold ink printing process

gold ink printing generally adopts neutral or neutral hard lining, and the pressure of inking roller on the printing plate cannot be too large, otherwise it will cause the phenomenon of plate pasting

during printing, when the gold ink layer on the printing plate is transferred to the surface of paper or other substrate, the ink volume is often insufficient, or even the bottom is exposed. Therefore, in order to saturate the gold ink and fully show its unique metallic luster, the secondary printing method is generally used. At present, there are basically two methods of secondary printing: first, printing fake gold ink as the background color, and then overprinting gold ink; The second is to directly print gold ink twice. The fake gold ink used in the former method is generally mixed with transparent yellow or medium yellow ink. If the paper is loose and the flatness of the paper is poor, the fake gold ink is mainly medium yellow, and an appropriate amount of gold ink is added. If the paper is tight and smooth, use transparent yellow and a small amount of gold ink to mix fake gold ink. When printing, the ink volume of the background color should be as small as possible, and the tension/strain curve should be checked in more detail at a higher speed or when the load fluctuates, in the principle of no bottom exposure and no edge penetration. When the background ink is not completely dry, overprint the gold ink, and the ink volume can be slightly larger, so as to achieve the saturation state of the gold ink. When using the latter method, it is also a multi-purpose machine. It should be emphasized that it is appropriate to overprint the gold ink for the second time when the gold ink printed for the first time is not completely dry. This is because the gold powder in the gold ink is a metal pigment. If it is printed after it is dry, its particles are not easy to stick

3. Notes for gold ink printing

(1) the nature of paper

the nature of paper will have a great impact on the quality of gold ink printing. Complete the tensile, compression and bending tests on the sample. The higher the smoothness and tightness of the paper, the better the metal effect of printing; On the contrary, printing on paper with porous surface and rough texture will have a poor effect. In addition, the pH value on the surface of the paper should be greater than 5.5. Otherwise, when printing products are stacked and stored, the sulfate radical contained in the paper will cause the gold powder to change color and blacken, and even cause the gold powder to be corroded and disappear

(2) gold ink printing graphics and texts

the graphics and texts of the gold ink printing layout should not be too thin, otherwise it is easy to cause paste, and its reflection effect will become worse

(3) wear resistance

the wear resistance of the gold ink layer after printing is an important indicator to measure the quality of gold ink printing. At present, there are two measures to solve the wear resistance of gold ink: one is to use gold oil with slightly higher viscosity to prepare gold ink, and the other is that after printing, using bright paste to polish with accurate testing is far from enough

(4) gold ink discoloration

after the gold ink printing products are placed for a period of time, the gold powder will be invaded by sulfur, oxygen, moisture, etc. in the air, which will darken the gloss of the imprinted surface, or even blacken, affecting the product quality. This is what we usually call the discoloration of gold ink, which should be paid attention to in the process of printing storage

(5) gold ink and other color inks overprint

gold ink should be printed on dark ground as much as possible, such as printing gold on red, blue and black, with better effect, especially when printing gold ink on purple, black, dark blue and other colors

in addition, try to avoid printing ordinary color ink on gold ink. If you must print ordinary color ink on a large area of gold ink, you should first reduce the viscosity of the ordinary ink, and you must wait until the gold ink is completely dry before printing, otherwise it will cause the gold ink text to bloom

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