Lithography from the greasy cause of the solution

The greasy print of lithographic printing is mainly in the form of graphic lines that spread out without being clear and complete. In blank areas, there are dirty ink marks ranging from light to heavy, and in particular blankets are also covered with a piece of ink. The reason is:

(1) The water-absorbing portion on the printing plate forms an ink-absorbing center, resulting in migration of the surfactant in the paper or plastic ink layer to the water-absorbing zone.

(2) The pH difference between the ink and water is too large (that is, the ink and ink is often unbalanced), which results in the printing plate being discolored by the acid in the solution.

(3) When using dry syrup containing lead, especially when the amount is too much, the dry oil is destroyed by the highly acidic syrup, which is covered by a thin layer of ink (usually also leads to yellowing of the entire plate). ). This oil layer is dirty because the ink layer hinders the control of wetting.

(4) The ink is too oily and too thick, resulting in insufficient amount of water on the plate.

(5) The non-printing area is deficient in induction processing and the pressure of the ink roller is large, the desiccant is unduly added, and the water roller is poor in quality or poor in installation. 

General processing method

(1) The pH of the ink should be lowered to approach the pH of the syrup;

(2) adding wax or sodium silicate to the ink;

(3) Check the quality of printing plates and water rollers;

(4) Control the printing speed;

(5) The ink is as thin as possible;

(6) Choose a small, thick oily ink.