One, dirty
Generally refers to the non-graphic area to produce dirt. It also includes the phenomenon of imprinting auxiliary, paste, and even dot network. However, the dirt can be divided into two kinds of situations: floating dirt and oil dirt. The breakdown is as follows:
1, floating dirty phenomenon: in the non-graphic area produces pale stains, because it is not dyed from the plate, so it is easy to erase.
the reason:
(1) The main reason is that the ink is relatively soft. After the action of the fountain solution, some inks enter the fountain solution due to emulsification to form an oil-type emulsion in water.
(2) Chemicals and wetting agents in the paper promote ink emulsification.
(3) The fountain solution contains soaps or detergents to cause ink emulsification.
Approach:
(1) Replace with high-viscosity, thicker, hard-to-emulsion inks, or add high-viscosity varnish to the original ink.
(2) Change paper.
(3) Adjust dampening fluid composition and pH.
2. Dirty phenomenon: The non-graphic area of ​​the printing plate becomes fat-sensitive. The ink adheres to it and contaminates the printed matter.
the reason:
(1) The ink is soft and lean.
(2) Too much ink.
(3) Free fatty acids, resin acids, and surfactants are present in the ink.
(4) The effect of the treatment agent in the pigment.
(5) The pressure of the ink roller dampening roller and the blanket is too large, and the surface structure of the printing plate is damaged.
(6) Dissolve lipids from the paper coating.
Approach:
(1) Replace the ink or add high viscosity resin oil (or oil No. 0) and gum oil to the original ink to make the ink sticky and elastic.
(2) Adjust the ink supply.
(3) Adjust the appropriate amount of fountain solution.
(4) Use a fountain solution with a higher surface tension.
(5) Adjust the pressure.
(6) Replace the paper.
Second, the bad phenomenon of overprinting: The ink printed on the back during wet overprinting cannot be smoothly attached to the ink printed first.
the reason:
(1) The viscosity of the ink after printing is too high compared to the ink printed beforehand.
(2) The first printing ink is slow and has a large amount of ink.
(3) The color intensity balance of the four-color ink is not appropriate.
Approach:
(1) Printing with high viscosity inks first, printing with low viscosity inks, and the ideal stickiness requirement should be gradually reduced in the order of overprinting colors.
(2) Fast and fast ink printing is used, and the high density is printed thinly. The pattern area is small and printed beforehand to facilitate the overprinting.
(3) The color intensity of any set of wet multi-color overprint inks is balanced. When overprinting, the same amount of ink can be used. If not using the same set of inks together, it should be handled properly. (Shanghai Peony Ink Co., Ltd.)
Generally refers to the non-graphic area to produce dirt. It also includes the phenomenon of imprinting auxiliary, paste, and even dot network. However, the dirt can be divided into two kinds of situations: floating dirt and oil dirt. The breakdown is as follows:
1, floating dirty phenomenon: in the non-graphic area produces pale stains, because it is not dyed from the plate, so it is easy to erase.
the reason:
(1) The main reason is that the ink is relatively soft. After the action of the fountain solution, some inks enter the fountain solution due to emulsification to form an oil-type emulsion in water.
(2) Chemicals and wetting agents in the paper promote ink emulsification.
(3) The fountain solution contains soaps or detergents to cause ink emulsification.
Approach:
(1) Replace with high-viscosity, thicker, hard-to-emulsion inks, or add high-viscosity varnish to the original ink.
(2) Change paper.
(3) Adjust dampening fluid composition and pH.
2. Dirty phenomenon: The non-graphic area of ​​the printing plate becomes fat-sensitive. The ink adheres to it and contaminates the printed matter.
the reason:
(1) The ink is soft and lean.
(2) Too much ink.
(3) Free fatty acids, resin acids, and surfactants are present in the ink.
(4) The effect of the treatment agent in the pigment.
(5) The pressure of the ink roller dampening roller and the blanket is too large, and the surface structure of the printing plate is damaged.
(6) Dissolve lipids from the paper coating.
Approach:
(1) Replace the ink or add high viscosity resin oil (or oil No. 0) and gum oil to the original ink to make the ink sticky and elastic.
(2) Adjust the ink supply.
(3) Adjust the appropriate amount of fountain solution.
(4) Use a fountain solution with a higher surface tension.
(5) Adjust the pressure.
(6) Replace the paper.
Second, the bad phenomenon of overprinting: The ink printed on the back during wet overprinting cannot be smoothly attached to the ink printed first.
the reason:
(1) The viscosity of the ink after printing is too high compared to the ink printed beforehand.
(2) The first printing ink is slow and has a large amount of ink.
(3) The color intensity balance of the four-color ink is not appropriate.
Approach:
(1) Printing with high viscosity inks first, printing with low viscosity inks, and the ideal stickiness requirement should be gradually reduced in the order of overprinting colors.
(2) Fast and fast ink printing is used, and the high density is printed thinly. The pattern area is small and printed beforehand to facilitate the overprinting.
(3) The color intensity of any set of wet multi-color overprint inks is balanced. When overprinting, the same amount of ink can be used. If not using the same set of inks together, it should be handled properly. (Shanghai Peony Ink Co., Ltd.)
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