When many printing factories use fountain solution, they only need to pay attention to the pH of the fountain solution within the required range (pH value is 5.0 to 5.4), and ignore the concentration of fountain solution. In fact, when the concentration of the fountain solution changes greatly, its pH change is not obvious. Therefore, it is unscientific to control the pH value only. Because the change of the concentration will change its composition, which will affect the balance of water and ink; the change of the concentration of the fountain solution will also cause the change of the concentration of the surfactant, which will cause the change of the surface tension, and finally affect the dampening effect, resulting in print quality decline. Therefore, the concentration of fountain solution is a key factor affecting the quality of printing. We must control the concentration of fountain solution while maintaining a stable pH.
Determine conductivity
The dampening effect can be measured by measuring the conductivity of the fountain solution. Within a certain pH range, the conductivity is greatly changed. Through experimental determination, the concentration of the fountain solution changes with its conductivity. This kind of linear relationship, that is, the greater the concentration, the greater the conductivity, so a certain value should be found within the range of change as its best wetting effect value. There are many other factors that affect the conductivity. Experiments show that for the same fountain solution, it is prepared with water from different places. Even if the same concentration of fountain solution is prepared, their conductivity is not the same, because it is different from the water. The degree of softness (how much Ca2 + and Mg2 + are in the water) is related. If the same kind of water is mixed with different brands of fountain solution to make fountain solutions of the same concentration, the conductivity is also different. The conductivity is large, indicating that there are many ions in the solution, and some ions have an effect on printing. If the concentration of Ca2 + and Mg2 + in the fountain solution is too high, it will cause the emulsification of the ink and hinder the drying of the blot. Moreover, during the high-speed printing process, due to temperature factors, Mg (HCO3) 2, Ca (HCO3) in the fountain solution 2 Decompose to produce CaCO3 and MgCO3 which are insoluble in water, and adhere to the water roller, which is easy to prevent water supply and cause dirty plate faults. Therefore, it is necessary to soften the water before formulating.
Due to the above factors, before formulating the fountain solution, we should ensure that its pH value is between 5.0 and 5.4 according to the quality of the water used, and then through the experimental method, measure the conductivity at different concentrations and draw the conductivity The range of the rate, and then in this range, find a certain conductivity value by the quality of the printed matter, as the standard value of the fountain solution prepared later using this fountain solution. Different water quality, different fountain solution, the conductivity value to achieve the best wetting effect is different, can not be generalized, before the trial, you can test according to the above method, maybe the best wetting effect may be achieved, you may wish to try .
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