In the process of packaging bag printing, the color of the ink film of the color printing packaging bag mainly depends on the concentration and transfer rate of the ink in the printing work. For some specific substrates or specific working inks, the concentration of working inks is relatively fixed, and the transfer rate depends on factors such as the viscosity of the ink, and is also affected by factors such as printing speed. It should be noted here that these elements will affect the highlights, shadows, and midtones of the print differently when they are changed. 1, temperature and humidity changesIf the room temperature and the liquid temperature of the ink are greatly changed, the migration state will change, and the color tone will change accordingly. This is because temperature changes affect ink viscosity. At the same time, the dry weather of high temperature and low humidity will have a significant impact on the ink transfer rate of the high-gloss parts.Therefore, when printing high-end products, the temperature and humidity of the printing workshop should be controlled anyway. In addition, when using ink in winter, it should be preheated in advance to reduce the temperature change of the ink itself. 2, separation of synthetic colorsThis phenomenon is prone to occur in pale colors and mixtures of various colors such as organic colors and inorganic pigments with widely different specific gravity. Especially when the ink flow in the ink tray is too slow, the precipitation will promote the separation of synthetic colors, so pay attention to making the ink circulation smooth.In addition, if the stirring is not sufficient during toning, the concentration of a certain color tends to increase as the printing progresses, so before the formal printing, a machine such as a dissolving machine or other methods should be used for sufficient stirring. 3, The ink is deteriorated and the color is deterioratedDue to long-term printing, the composition of the ink solvent changes, or the moisture in the air is mixed into the ink to cause the ink to deteriorate, making the color worse.In order to prevent the temperature drop due to the heat of vaporization, a slow-drying solvent can be used together. At high temperature and high humidity, a certain amount of water may be mixed into the ink, so when the abnormality occurs, new ink should be added, or all replaced. The remaining ink that has been used many times should be filtered or discarded regularly because a lot of dust is mixed in. . 4The working viscosity and drying speed of the ink are changedChanges in the working viscosity of the ink can directly affect the color of the printed product. When the viscosity is high, the color density is relatively high, and vice versa, when the viscosity is low, the color density is relatively low. This effect is sometimes very obvious and must be highly regarded. Because of the requirements of the printing process, the working viscosity of the ink should be moderate. When the working viscosity of the ink is too large, it is not conducive to the transfer of the ink, and it is easy to produce a paste phenomenon. If the working time of the ink is too small, the color of the printed product is prone to electrostatic phenomenon, which is not conducive to the control of the ink color.Changes in viscosity have a subtle effect on the transfer area caused by the flow of ink or the flow of dots, especially in multi-color printing. Therefore, when the printing speed is certain, the viscosity of the ink is required to be consistent from beginning to end, and it is best to use an automatic viscosity controller.When the solvent ratio in the ink is changed, the drying speed of the working ink will change.
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