Application of pH meter and conductivity meter in printing industry
Measurement and monitoring of paper pH
1. PH value affects printing properties such as ink and ink balance
In offset printing, the pH value of paper and fountain solution will directly affect the ink balance of the printing process, the drying performance of the ink and the quality of the ink layer. Therefore, when controlling and adjusting the ink balance, it is necessary to understand the acidity and alkalinity of the paper and fountain solution. Industrial pH meters can help measure and monitor changes in the pH value. To understand its impact on the printing process.
2. PH value is the primary factor to improve printing quality.
As the market's requirements for printing quality are getting higher and higher, coupled with the advancement of printing technology, the impact of paper characteristics and its printability on printing quality has begun to receive attention, and the pH value of paper is a factor that should be controlled.
3. Effects of too low PH value
When the pH value of the paper is too low, the acidity of the fountain solution will be significantly enhanced, thereby inhibiting the oxidative polymerization reaction and drying speed of the ink, causing the printed matter to dry out.
4. The best PH value range for printing
If the pH value of printing paper is neutral, the printing quality can be greatly improved. However, due to factors such as raw materials and processing technology in paper production, there is no neutral paper with a pH value of 7. The surface of printing paper or coating layer often has a certain acidity or alkalinity. When the pH value is 7, the paper surface Alkaline. At present, my country's papermaking mainly uses alkali pulping, using NaOH as the cooking agent, so most paper is slightly alkaline. If the alkalinity is too high, the acidity of the fountain solution will change significantly, which will weaken the acidity of the hydrophilic glue layer in the non-graphic and text parts of the printing plate. If it cannot be adjusted in time, it will inevitably cause a decrease in the hydrophilicity of the non-graphic and text parts and an imbalance of ink and water. , the tinting power of the ink decreases, resulting in dim color of printed images and texts, and even deinking of patterns, pasted plates and ink rollers. At the same time, those weakly alkaline fibers that fall off the paper coating will be transferred to the blanket, and then transferred to the printing plate through the blanket, causing the printing plate belt to become dirty and the printing durability to decrease. Precise control using industrial pH meters is very necessary to improve printing quality.
The necessity of using industrial conductivity meters
1. Control conductivity to ensure stable PH value
In order to ensure that the pH value of the fountain solution is relatively stable, the advanced method is to monitor the conductivity of the fountain solution while controlling the amount of buffer added and the hardness of the water.
2 Because as the concentration of the fountain solution increases, the hardness of the water and the temperature of the water increase, the conductivity of the fountain solution will increase and the pH value will decrease; on the contrary, if alcohol is added to the fountain solution, the Conductivity decreases and pH increases. Tested by an industrial conductivity meter, the conductivity of fountain solution should generally be controlled at (1400±200)μs/cm. However, due to the influence of dust, ink and other mixed substances, the conductivity is also within the range of 800μs/cm~2000μs/cm. This is allowed, but when the fountain solution appears to be visibly contaminated, it must be reconstituted.
