(16) poor gloss
1. Phenomenon : the ink seeps into the paper and makes the printed matter uneven and dull.
2. Reason : The link material in the ink is too thin. The ink dries too slowly. Paper is too absorbent.
3. Solution : Check the drying time of the ink, if it is too slow, you can add some cobalt drying oil. Add a small amount of bright linking material, varnish or resin linking material. Use poorly absorbent paper.
(17) DRY TOO FAST
1. Phenomenon : The ink dries too quickly in the ink fountain and on the machine, so there is a phenomenon of thickening on the machine, and the phenomenon of napping and ink accumulation may also occur.
2. Reason : Too much desiccant in the ink or too much intense desiccant. The ink contains solvents that evaporate too quickly. The printing room is too hot, too dry or the windows are opened too much.
3. Solution : Add a small amount of vaseline, castor oil or paraffin oil to the ink to reduce its dryness. Add a small amount of anti-skinning agent or anti-oxidant, such as methyl ethyl ketone oxime and so on. Not too ventilated and protected from the sun on hot days.
(18) Fading
1. Phenomenon : the color of the ink fades during printing, or the color of the ink fades during the stacking of printed matter (during the drying process). This is common for parts printing, because the colors of this type of printing are various, and there are many so-called small colors (light colors), and the content of a certain pigment in the small colors is very high. Less.
2. Reason : In the paper pile, due to the oxidation of the ink, heat is generated, which will fade some colors, especially in the middle part of the paper pile. Too much cobalt driers in the ink. The pigment is not heat-resistant or the pigment content in the ink is too small. The pigment in the white oil explosion is reactive when used with light-colored ink (for example, zinc oxide is more reactive than titanium dioxide).
3. Solution : Use quick-drying (or fast-curing) ink to use less desiccant. Use slurry desiccant. Heat-resistant and light-resistant stable pigments are used in the ink. Replace with white paint or filler.
(19) weak color
1. Phenomenon : The coloring strength of the ink is qualified and meets the standard during the inspection, but the color of the printed matter is still insufficient.
2. Reason : The linking material in the ink is too thin, and the ink seeps into the paper. Prints lack luster. In the later stage of drying, the surface of the printed matter is dirty.
3. Solution : The linking material in the ink should be thicker. A fast-drying resin-based linking material is used, which dries to a glossy finish, giving the appearance of increased color intensity. The inks are manufactured using different pigments, which allow for clean and not dirty post-drying. Cover with a layer of varnish, so that it looks like the underlying layer of color is full and bright.
(20) Overprint performance
1. Phenomenon : The so-called overprint performance refers to the transfer of one layer of ink film to another layer of ink film in multi-color printing. A flat and uniform transfer is said to have good overprinting performance.
2. Reason : Due to the inconsistent wetting of the first color ink film, the second color ink lacks adhesion to the first color oil. Vibrations are induced in the two ink films, and collisions occur at the interface. A membrane that absorbs a large amount of energy will not break and still exist. It will move when touched, while a membrane with a low viscosity energy density will separate in the membrane. This separation should be adjusted so that the new oil baby just overprints within a given time.
3. Solution : maximize the adhesion of the second color ink film, and then cover (press) it. It is conceivable that the proper conditions for overprinting should be during the tackification period of the ink film. Overprinting on transparent or already crystallized ink films is not satisfactory. Adjust the dryness of the primary color to make it suitable for overprinting. The viscosity of the overprint ink should decrease in turn. Since the ink will be sheared at the moment of printing, the ink viscosity meter can be used to determine the sequence in wet multi-color overprinting at a given speed. The viscosity at low shear ratios is very different from the viscosity at high shear ratios. For non-absorbent surfaces (such as aluminum foil, etc.), the body and viscosity of the ink are very important, and it should be adjusted carefully, and the requirements for overprinting conditions are also stricter.
(21) Streaks
1. Phenomenon : Due to the irregular movement between the roller and the printing plate (mainly the fault of the roller), the result is that the ink is concentrated on the edge of the plate to form slight streaks.
2. Cause: A ridge line is formed by pushing excess ink to one side due to the uneven adjustment of the roller.
3. Solution: adjust the roller to be flat.
(22) Cover light penetration
1. Phenomenon : One is that after using alcohol-soluble varnish, the dot film of the printed matter is not clear, and there is bleeding around the imprint. Sometimes the color of the bleed is different from the top color of the original print.
2. Reason : The ink is not dry enough. The ink is not resistant to alcohol solvents. Pigments in inks such as Faneuil-type lake pigments are not resistant to alcohol-based solvents. ·
3. Solution : Use oil-type varnish instead. Overprint a layer of lightening agent on the printed matter first, and then cover it.
