Small offset printing experience: the printing process must grasp the water and ink
Offset printing is done by applying the principle of incompatibility between water and ink. If the moisture is too small, it will inevitably lead to an increase in solid density, an increase or deformation of the dot area of ​​graphics and text. In severe cases, it will produce a paste version, and some parts are easy to get dirty, making the imprinting level ambiguous. To form waste products.
Excessive moisture will easily cause emulsification of the ink under the action of mechanical pressure, reduce cohesion and water resistance. The greater the moisture, the longer the time, the more serious the emulsification, and the more severe the damage level of the ink printing suitability. As a result, the ink accumulates on the ink roller and the printing plate, and cannot be transferred normally, forcing the printing job to be infixed, so the water roller has to be washed again, and new ink is changed. Due to the emulsification of the ink, the ink color becomes lighter, the saturation and viscosity drop sharply and the adhesion is weakened, which causes the graphic dots to be deformed, barbed, and not bright, resulting in paste and other phenomena. Especially after the dots are stacked, the ink layer is thin and dull, the layer is unclear, and there is a big color deviation.
If the moisture is too large, the printed paper will be stretched due to the absorption of excessive moisture. During storage, the four sides of the paper will naturally release moisture, and the irregular expansion and deformation will be large, resulting in inaccurate or almost impossible overprinting.
Excessive moisture will also affect the dryness of the blot at different levels. The ink is dried by the penetration of the binder and the volatile conjunctiva. When it contains a large amount of water, it is difficult to soak, and it also prolongs the time of the volatile conjunctiva. Sometimes it is difficult to dry, which affects the continued overprinting, and it is also easy to form the reverse side of the printed product.
The water and ink balance of offset printing is maintained under the influence of various variables in the mechanical movement and printing process. Therefore, there are many factors that affect the balance of ink and wash, and they are more complicated, but there are also rules to follow. The general criterion is: "Water follows ink".
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