Fountain solution as an important raw material for offset printing process has a great influence on the quality of offset printing products. In order to make offset printing graphic printing ink bright, clear, blank parts are not sticky, must be based on the printing conditions reasonable allocation of fountain solution concentration, to avoid the printing process of poor printability defects, to ensure offset printing product quality.
The concentration of the offset fountain solution is measured by the addition and discharge of the stock solution. How to accurately grasp the amount of fountain solution added and discharged, so that offset printing syrup to play the best effect, is a more complex problem. Because of the actual printing quality, it is not determined by one or two factors. Due to the difference in printing conditions, the fountain solution concentration must also be different. Therefore, there is no specific numerical value for the concentration of the fountain solution as a standard, but it can only be grasped by practical experience and the methods of “prepress estimation” and “printing adjustment”. In general, the following situations have a certain influence on the concentration of fountain solution, which is worth understanding and mastering.
1. The difference of paper on the fountain solution concentration requirements
When the printed paper is loose in texture or contains sand and dust in the paper, due to the large viscosity of the printing ink, the paper wool and sand (powder) often deposit on the blanket, which will inevitably increase the friction of the printing plate film. It is easy to get dirty due to wear. In this case, the amount of liquid should be appropriately increased. When printing white and tough paper, especially when printing coated paper, the amount of raw liquid should be appropriately reduced. In order to prevent the use of more orange liquid, it will make printing paper yellow and affect the quality of printed products.
2. The difference in the characteristics of the ink on the volume of the liquid plus volume requirements
Due to the difference in printing inks, the nature of pigments, oil content, oiliness, viscosity, flowability, and acid resistance are also different, and the reaction to the concentration of the fountain solution is correspondingly different. Therefore, the concentration of the fountain solution should be adjusted as appropriate. In general, the concentration of fountain solution used for printing red ink is higher than that of printed black ink, while black ink is higher than blue ink, blue ink is higher than yellow ink, and dark color is higher than light color.
3. The amount of driers in the ink
When printing multi-color plate products, the dry oil is added to the ink to speed up the drying of the ink. At the same time, the particles of the ink become thicker and the viscosity increases, so that the sense of grease on the blank area of the printing plate is increased, so that the paste plate is easily generated. Due to this situation, the amount of fountain solution should be appropriately increased.
4. Differences in printing layout requirements for fountain solution
Due to the wide variety of printed products, there are both printed on-site layouts as well as printed lines and dot layouts. If the layout is dominated by lines and solid shades, and the ink-receiving area is small, the concentration of the fountain solution should be adjusted to be larger, so that the blank layout is not easily sticky. If the whole plate is composed of dots, the amount of raw liquid should be reduced. As for printing plates with both the field and the dot, it should be considered comprehensively to ensure the stability of the printing quality.
5. Printing shop temperature requirements for fountain solution
When the temperature of the printing environment increases, the molecular motion of the material will inevitably accelerate, and the fluidity of the ink will become thinner, and at the same time, more free fatty acids will be decomposed, so that the printing plate will be prone to stickiness. Therefore, the dampening is appropriately increased at high temperatures. The amount of raw liquid.
6. Printing ink layer thickness requirements for fountain solution
In the printing process, due to the increase in ink layer thickness, the amount of ink transferred in the ink fountain must also increase accordingly, and the amount of ink received by the layout graphics and text base has a certain limit, so that when the ink roller is used to brush ink, the ink layer must be pressed against the blank layout. Influencing its hydrophilic properties, it is necessary to appropriately increase the amount of dampening stock solution to achieve the relatively stable hydrophilic properties of blank areas.
In addition to the above, if the printing pressure is large, and the blanket and liner are hard, the concentration of the fountain solution should be appropriately increased to achieve a better anti-dirty effect. All the above-mentioned situations are relative, so when considering the amount of raw liquid to be added and discharged, comprehensive consideration must be taken. In general, the principle of using as little liquid as possible should be taken into consideration, observe the changes in the conditions during the printing process, and adjust the proper concentration of the fountain solution in a timely and accurate manner so as to achieve the purpose of improving the printing quality.
Puyang Longfeng Paper Co.,Ltd. , http://www.lonfonpaper.com
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