The binder used in ink is mainly alkali-soluble acid resin, so the control of pH value is very important. Generally, the pH value should be controlled at 8.5 to 9.5. At this time, the printing performance of ink and water is the best, and the printing quality is the most stable.

Because the amine is constantly volatile during the printing process, the operator still needs to add new inks and various additives from time to time, so the pH value of the ink is changing at any time. When the pH of the ink is higher than 9.5, the alkalinity is too strong, the viscosity of the ink will decrease, resulting in slower drying speed and poor water resistance; when the pH value is lower than 8.5, the alkalinity is too weak, and the viscosity of the ink will increase High, resulting in faster drying speed, easy to block the printing plate and anilox roller, causing the plate to be dirty, and air bubbles will be generated.

Since the influence of pH value is directly related to viscosity, it is recommended to control the two in actual printing, especially in process printing, this problem should be paid more attention to. Generally, in addition to the viscosity cup, a simple pH indicator should be prepared for testing at any time. When the pH value of the ink is low, a pH stabilizer or a small amount of an alkaline substance may be added; when the pH value is high, a solvent or a diluent may be added for dilution.