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Analysis of materials and technical application of gold and silver ink printing (III)

(2) offset gold and silver printing process offset gold and silver ink printing has the characteristics of fast speed, simple process and good effect, so it is widely used in packaging printing. Due to the fact that the offset printing process is based on the principle of water ink balance, which makes use of the immiscibility of water and ink and the total output value of the modified plastic industry to reach 5billion yuan by 2020, the gold and silver powder in the gold and silver ink has high density, large particles, poor printing adaptability, and it is easy to change color in case of acid wetting liquid, so these problems should be paid attention to when printing

① offset printing drives related industries to increase, and the indirect economic benefits can reach us The formula of gold printing silver ink of more than 50000 billion yuan

field and line printing gold ink. 100g 1000 mesh gold powder, 80g gold blending oil, 20g transparent yellow ink. Or 200g 1000 mesh gold powder, 100g gold mixing oil, and an appropriate amount of dry oil

gold ink is printed twice on the field and line version. First printing gold ink: 200g 1000 mesh gold powder, 200g gold mixing oil, 200g transparent yellow ink, and an appropriate amount of dry oil; The second printing gold ink: 200g 1000 mesh gold

powder, 100g gold blending oil, 100g transparent yellow ink, and an appropriate amount of dry oil

gold ink with gold printed on the line. Gold blending oil 40%, transparent diluted ink 40%, phenolic resin 20%. After the binder is prepared, it is mixed with 1000 mesh gold powder in 1:1 to form gold ink

ancient paintings are printed with gold and ink. Mix 100g resin and 100g gold blending oil first, then add 200g 1000 mesh gold powder, 3G gold blending oil and a proper amount of dry oil

when preparing offset printing gold ink, we should pay attention to the proportion and technical indicators of gold powder and gold blending oil, and make corresponding adjustments according to the changes of climate and environment around the country and the selected printing machinery

offset silver ink (by weight). Silver paste 60%, silver ink 40%, of which resin based silver ink composition: phenolic resin 70%, flaxseed oil 30%; The composition of silver blending oil dominated by gloss oil is: gloss oil 35%, dibutyl phthalate 62%, red dry oil 3%

② choose the offset printing gold and silver fountain solution

the wetting solution should be acidic from time to time, because the gold and silver powder is easy to turn black when encountering the acidic fountain solution. Alcohol wetting liquid is suitable because it has the advantages of less oxidation of gold and silver powder, less discoloration of gold and silver powder, less water consumption for wetting the layout, and easy to achieve ink and water balance

the amount of wetting solution for the layout should be controlled at the minimum water standard under the premise of "no paste". Too much water is easy to emulsify gold and silver ink and affect the printing quality

neutral or hard lining should be used. Because the lithographic offset printing speed is fast, the contact time between the printing plate cylinder and the rubber cylinder, the rubber cylinder and the paper is short, and the transfer performance of the gold silver ink is poor, the ink layer is required to be flat and thick, so it must be solved by increasing the pressure. However, increasing the pressure on the soft lining is easy to compress and deform, causing the gold and silver dots to expand and paste, so the medium and hard lining is generally used to achieve the purpose of reducing the compression deformation of the lining and increasing the pressure

the color sequence of gold and silver ink printing is the last color, and the reasons are as follows:

if gold and silver are placed in the front color sequence printing, when the viscosity of the latter color ink is greater than that of the former color, it is easy to peel off part of the gold and silver ink of the former color, resulting in less gold and silver ink, dullness, and color mixing

if gold and silver are placed in front of the color sequence printing, the gold and silver color will oxidize and change color because the gold and silver ink must contact with the wetting solution again or more times when one or more colors are printed

the bottom ink must be thick and smooth. In addition, gold and silver ink overprint must be carried out when the bottom ink seems to be dry rather than dry. The so-called "dry but not dry" means that when the hand contacts the bottom ink layer, it feels sticky, but the ink does not stick to the hand

③ color sequence selection

printing color sequence of four-color offset press

the printing color sequence of four-color offset press is generally black, cyan, magenta and yellow. The transfer of printing inks of various colors is carried out "wet" under the state of high-speed operation. If the thickness of the ink layer printed on the paper is greater than that on the blanket of the next unit, the ink layer fracture will occur on the paper. At this time, the ink on the blanket is not only not transferred to the paper. Instead, it will accept the printed ink of the previous color from the paper, resulting in a "reversal" phenomenon. This "wet press wet" overprint method brings a lot of inconvenience to the printing of gold ink and silver ink, and the printing effect is not very ideal

in order to overcome the above adverse factors, the following solutions can be taken to print gold ink and silver ink with a four-color offset press. When printing gold ink and silver ink, increasing the amount of ink (that is, increasing the thickness of the ink layer) can eliminate the "reversal" phenomenon. However, small hollow words are easy to paste, difficult to operate, and waste ink, increasing the printing cost.

put the color plate with short tone and thin printing ink layer on the previous unit of the printing gold ink unit

printing color sequence of monochrome Offset Press

monochrome offset press prints the next color ink after the previous color ink layer is basically dry. It adopts the "wet press dry" overprint method, and does not pay much attention to the arrangement of color sequence. There are no problems in the "wet press wet" printing of four-color offset press at all. Moreover, in response to the company's order to "reduce costs and increase efficiency", the ink transfer rate of monochrome Offset Press is higher than that of four-color offset press in the case of equal transfer. That is to say, the ink is easy to pile up on the prints printed by the monochrome Offset Press, and the ink layer is much thicker than that produced by the four-color press. Due to different overprint methods, monochrome Offset printing machine provides favorable conditions for gold ink and silver ink printing

the advantages of printing gold ink and silver ink with monochrome machine are:

the drying speed of imprinting is accelerated

reduces ink penetration, and less ink can reduce printing costs and restore authenticity

prints have strong gloss and good visual effect

its disadvantage is that the printing production cycle is longer than that of the four-color offset press

the semi-finished products printed by the monochrome machine cannot be stored for a long time, otherwise it is easy to produce crystallization, resulting in the failure of subsequent color ink printing

influence of lining selection

four color offset printing machine has high requirements for rubber and lining when printing gold ink and silver ink, because the printing speed of the four-color offset printing machine is fast, and the contact time between the back color ink and the front color ink layer is very short, which is easy to cause galling and gold and silver ink paste failure. This requires both increasing the printing pressure and preventing excessive deformation. Therefore, only medium and hard liners can be used to reduce compression deformation and increase the printing pressure

its advantage is that the pressure generated by the medium and hard lining is relatively large, which accelerates the speed of ink penetrating into the interior of the paper, and the ink does not float on the surface of the paper; The ink layer is uniform and smooth.

its disadvantages are: high requirements for rubber and lining, which increases the printing cost; The operation is cumbersome

④ the lining problem of monochrome offset press

monochrome Offset Press does not have high requirements for rubber and lining when printing gold ink and silver ink. Because its speed is slower than that of four-color press, and it adopts the "wet press dry" overprint method, gold and silver ink is easy to pile on the paper when printing. Neutral or soft lining can be used when printing gold and silver ink with monochrome machine. Neutral lining, domestic rubber blanket, plus Farsi backing cloth or paperboard (better hardness). The effect is good if the pressure is slightly increased.

its advantages are: good lining adaptability and low printing cost; Easy to operate; The printing ink layer is thick and shiny

⑤ heald table problems needing attention

humidity control: the fountain solution must not be used with red potion, because it will cause oxidation reaction of gold ink and silver ink, color change and loss of gloss. 'Lide' powder can be used instead

the best wetting method: alcohol moistening. The advantages of alcohol fountain are as follows: alcohol wet solution has little oxidation to gold ink and silver ink; The water consumption of alcohol wet version is small and the wetting area is large, so it is easier to achieve the balance of water and ink; Alcohol wet plate can volatilize the heat generated by the high-speed friction of the ink roller, avoiding the oxidation and blackening of gold and silver ink due to high temperature.

priming before gold and silver printing: the pigment particles of gold and silver ink are relatively thick, which has the disadvantages of poor brush suitability and low adhesion compared with general color offset printing ink, so it is better to apply a layer of background color before printing gold and silver ink

the colors of various papers are different, including blue light and yellow light. Generally, the blending of the base color depends on the hue of the paper.

generally, the base color of gold printing is mainly yellow, but also black. The base color of silver printing is generally based on light ink, or white ink is added to the silver ink during the first silver printing. Then we will print silver for the second time

⑥ the preparation requirements of gold and silver content such as foot switch

deploy gold ink, and the ink blending oil value used for silver ink should be low. The inking oil must be transparent. It has the properties of fast drying and fast fixation. Gold ink should be adjusted with printing, because copper is easy to oxidize. When adding gold powder, it should be fully mixed, and kerosene should be properly added. When mixing silver ink, generally, the silver paste accounts for about 57%, and the silver mixing oil accounts for about 43%. In addition, some kerosene is added appropriately

⑦ printing suitability of gold ink and silver ink

the picture of printing gold and silver should not be too small. Small hollow words should not be printed with gold and silver ink as far as possible. The substrate color is required. As far as possible, paper with high surface smoothness such as coated paper and paperboard should be used for large-area gold and silver ink printing. It is best to use medium hard lining

the pressure between the printing plate and the inking roller should be appropriately reduced to ensure that the gold and silver printing pictures and texts are not deformed, while the pressure between the inking roller and the inking roller can be appropriately increased

(to be continued)

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