Dampening solution concentration control
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In many printing plants, when using dampening solution, only the pH of the dampening solution should be controlled within the required range (pH 5.0-5.4), and the concentration of dampening solution is neglected. In fact, when the concentration of the fountain solution changes greatly, its pH change is not obvious. Therefore, it is unscientific to control only the pH value. Because the change of concentration will change its composition, thus affecting the balance of ink and water; the change of the concentration of dampening solution will also cause the change of surfactant concentration, which will cause the change of surface tension, and finally affect the dampening effect, resulting in the quality of printed products. decline. Therefore, the concentration of dampening solution is a key factor in the quality of the printed product. We must control the concentration of dampening solution while maintaining a stable pH.
Determination of conductivity
The dampening effect can be measured by measuring the conductivity of the dampening solution. The conductivity of the dampening solution varies greatly within a certain pH range. The change of the concentration of the dampening solution and its conductivity change are determined by experiments. A linear relationship, that is, the greater the concentration, the greater the conductivity, so a certain value should be found within the range of variation as its optimal wetting effect value. There are many other factors that affect the conductivity. Experiments have shown that for the same dampening solution, it is prepared from water in different places. Even if the same concentration of dampening solution is dispensed, their conductivity is different, because this is related to water. The degree of hardness is related to the amount of Ca2+ and Mg2+ in the water. If the same water is mixed with different brands of dampening syrup to prepare the same concentration of dampening solution, the electrical conductivity is different, and the electrical 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+ or Mg2+ in the dampening solution is too high, the ink will be emulsified, which will hinder the drying of the blot. Moreover, in the high-speed printing process, Mg(HCO3)2 and Ca(HCO3) in the dampening solution will be caused by temperature factors. 2 Decomposition, the formation of water-insoluble CaCO3, MgCO3, attached to the water roller, easy to prevent the water, a dirty version of the failure, it is necessary to first soften the water, and then prepare.
Due to the above factors, we should ensure that the pH value is between 5.0 and 5.4 according to the water quality of the water used before preparing the dampening solution. Then, the conductivity of the different concentrations is measured by the experimental method, and the conductance is drawn. The range of the rate, and then within this range, find a certain conductivity value by the quality of the printed matter, as a standard value for the future use of this dampening solution to prepare dampening solution. Different water quality, different dampening syrup, the conductivity value of the best wetting effect is not the same, can not be generalized, before the trial, can be tested according to the above method, may achieve the best wetting effect, may wish to try .