Fountain solution concentration control

When many printers use the fountain solution, they only pay attention to the pH of the fountain solution to be controlled within the required range (pH 5.0 to 5.4), ignoring the concentration of the fountain solution. In fact, when the concentration of the fountain solution changes greatly, its pH value does not change significantly. Therefore, it is unscientific to control only the pH value. Because the change of concentration will change the composition of the ink, which will affect the ink balance; the change of the fountain solution concentration will also cause the change of the surfactant concentration, which will cause the change of the surface tension, and finally affect the dampening effect, resulting in the quality of the printed product. decline. Therefore, the concentration of the fountain solution is a key factor affecting the quality of the printed product. We must control the concentration of the fountain solution while maintaining a stable pH.

Determine the conductivity

The dampening effect can be measured by measuring the conductivity of the fountain solution. Within a certain range of pH, the electrical conductivity is greatly changed. Through experimental measurement, the concentration of the fountain solution changes with its conductivity. The 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 optimal wetting effect value. However, there are many other factors that affect the conductivity. Experiments have shown that for the same fountain solution, water is prepared in different places. Even if the same concentration of fountain solution is dispensed, their conductivity is not the same because it is different from that of water. How soft and hard (water contains Ca2+, Mg2+) is related. If the same kind of water and different brands of fountain solution mixed to make the same concentration of the fountain solution, the conductivity is not the same, the conductivity is large, indicating that the solution of more ions, some ions have an impact on the printing, If the concentration of Ca2+ and Mg2+ in the fountain solution is too high, the ink will be emulsified and the drying of the imprint will be hindered. Moreover, in the high-speed printing process, Mg(HCO3)2 and Ca(HCO3) in the fountain solution will be caused by temperature factors. 2 decomposition, the formation of insoluble CaCO3, MgCO3, attached to the water roller, easy to prevent the water, there dirty version of the failure, so it is necessary to make the water softened before preparation.

Due to the above factors, before formulating the dampening solution, we must ensure that the pH of the water is between 5.0 and 5.4, based on the quality of the water used. Then, by means of the experimental method, the conductivity at different concentrations is measured and the conductance is plotted. The range of the rate, and then within this range, a certain conductivity value is found by the quality of the printed matter as a standard value for the future use of the fountain solution to formulate the fountain solution. Different water quality, different dampening potions, and different conductivity values ​​to achieve the best wetting effect are not the same, so we can't generalize them. Before the trial, we can test according to the above methods, and we may achieve the best wetting effect, so we might try. .