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.
Reasons: (1) The main reason is that the ink is relatively soft, some of the inks are emulsified into the fountain solution after the action of the fountain solution, forming 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.
Treatment methods: (1) Replace the hard-emulsified ink with high viscosity and thick, 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 â€‹â€‹the printing plate becomes fat-sensitive, and the ink adheres to it, contaminating the printed matter.
Reasons: (1) 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.
Treatment methods: (1) Replace the ink or add high-viscosity resin oil (or No. 0 oil) 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. When (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.
Reasons: (1) The viscosity of the ink after printing is too high compared to the ink printed before. (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.
Processing methods: (1) Printing with high viscosity inks first and printing with low viscosity inks. The ideal stickiness requirements 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.
Phenomenon, when overprinting on the dry ink, it is possible that the overprinted ink will not be overprinted, and even if it is barely printed, the pool can be easily wiped off.
Reason: This is due to the fact that the first printing ink contains too much desiccant, the ink dries too quickly, the interval between printings is too long, and the surface of the ink film is formed by a smooth dura mater, which makes it difficult to ink the next color ink.
Treatment methods: (1) A reasonable understanding of the interval between overprints, inks printed before the first printed ink is completely dried. (2) reduce the amount of desiccant in the ink, slow down the ink drying speed. (3) If crystallization has occurred, remediate it by printing a resin binder or a 05-90 bright paste.
Phenomenon: When the printed matter is printed on the front side, the front side of the printed matter is stacked and the back side of the printed matter is overlapped and called dirty.
Reasons: (1) The fixing and drying of the ink is slow. (2) Ink is too large. (3) The paper surface is relatively tight and smooth and has poor absorption. Ink cannot penetrate and stick quickly on the surface of the paper.
Treatment method: (2) Change the fast fixing type ink. (2) Use thin layer printing with high-density ink. (3) Take the surface dusting method. (4) Add 59 anti-adhesion agent or six grain flour to the ink.
5. Stacking ink
Phenomenon: refers to the accumulation of ink on the blanket, plate and ink roller, poor transfer of ink transfer, so that the printed ink is blurred.
Reasons: (1) The ink is too short and lacks fluidity. (2) High pigment content, coarse particles, large specific gravity, insufficient grinding, insufficient wetting. (3) The viscosity of the ink and the binder is low, and milkiness occurs with the fountain solution. (4) The paper powder is peeled off and mixed in the ink to make the ink shorter.
Treatment methods: (1) Add a water-resisting resin binder that can make the ink longer. (2) Change the pigment with high concentration and reduce the amount of pigment and solids to re-roll the ink. (3) Minimize the amount of fountain solution. (4) Add some 05-92 detackifying agent to reduce viscosity. Replace paper if invalid.
Six, flying ink
Phenomenon: When the printing press is running, the ink is split between the ink rollers of the printing machine. The long ink forms long filaments. These filaments are broken into fine droplets and scattered in mist and distributed in the air of the printing shop.
Reasons: (1) Printing speed is too fast. (2) Too much ink, the ink layer on the ink roller is too thick. (3) The ink is too long and sticky. (4) The ink roller is not properly installed or damaged.
Processing methods: (1) Reduce the printing speed. (2) Change the ink with high color density to reduce the amount of ink. (3) Add wax additives to make the ink short and reduce the viscosity. (4) Check the ink roller and open the ink fountain smaller. Adjust the ratchet wheel to make the rotation faster.
Seven, ink does not fall
Phenomenon: The ink lacks fluidity during printing and cannot be transferred from the ink fountain to the ink roller.
Reasons: (1) The yield value of the ink is too large, and the ink ink has a short flowability. (2) Large thixotropy of ink.
Treatment methods: (1) Add a #3 varnish that can lengthen the ink, or a high-viscosity resin oil that improves ink flow. (2) Stir the ink often or install a stirrer in the ink fountain. (3) Change the ink with good fluidity.
Eight, paper lint or powder off
Phenomenon: When printing, fiber or filler particles are dropped from the surface of the paper and piled up on the graphic of the blanket, so that the quality of the print is reduced.
Reasons: (1) Poor paper quality. (2) The viscosity of the ink is high, or the viscosity is increased due to solvent evaporation in the ink. (3) Printing speed is too fast. Printing pressure is too high, causing paper
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