The water quality of the fountain solution is very important for the wetting system. Too hard water quality will affect the normal operation of the wetting system, and will affect the printing process and printing quality. In July 2003, the company installed a canopy reverse osmosis RO membrane pure water machine, which reduced the water hardness of the wetting system from 18 degrees to 2 degrees. The change of water hardness has the following impact on the actual printing process .
1. The ratio of various ingredients in the water tank and the nature of the water change
Improved the ratio of various ingredients in the water tank and the properties of the water. After switching to soft water, the hardness and chemical impurities decrease, and the electrical conductivity drops sharply. Moreover, due to the use of dampening stock solution suitable for soft water (cheaper than hard water) and reduced alcohol concentration, it reduces the consumption of raw materials while improving the quality of the wetting system.
2. It is helpful to solve the crystallization problem on the roller surface
The hardness of water mainly depends on the content of calcium ions and magnesium ions in the water. When the hardness of the water is too high, that is, when there is a large amount of free calcium ions and magnesium ions in the water, they will react with the pigment (especially magenta ink) to cause the pigment to separate and attach to the ink roller and rubber roller. A vitreous crystallized surface is formed, which affects the transferability of the roller to the ink. This problem rarely occurs because the content of calcium and magnesium ions in soft water is relatively small. Since the installation of the pure water machine by our company, there have been no printing failures such as insufficient ink transfer or no ink transfer due to the crystallization of the rollers, which often occurs before installation.
3. Conducive to the control of water and ink balance
Soft water mainly affects the water-ink balance from three aspects: (1) The decrease in hardness improves the spreadability of the fountain solution on the PS version, thereby reducing the amount of fountain solution. (2) After using soft water, roller crystallization rarely occurs, and the ink is very smooth during the transfer process. (3) The content of calcium ions and magnesium ions in soft water is small, which basically does not affect the printability of the ink, so it is easier to achieve the ideal water-ink balance with soft water.
4. Improve the printing quality
Before using soft water, our company basically used Tianjin Tianshi brand ink. When changing to other brand inks, magenta ink is very easy to paste in the fine layers formed by some dots, affecting the printing quality and efficiency. After using soft water, the phenomenon of paste plate disappears, and the wetting system of soft water can meet the printing conditions of ink to a large extent.
In China, especially in the north, water hardness is generally high, generally above 14 degrees, and printing requires water hardness below 8 degrees. Therefore, from the perspective of process improvement, water softening is very necessary for many printing companies .
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Zhejiang Changxing Hanghua Glass Co., Ltd. , https://www.hanghua-glass.com