Alcohol-free printing with alcohol substitutes is more likely to achieve water-ink balance. Printing with a specific thickness of ink film that has not been diluted with alcohol can produce higher quality prints with fine dots and less emulsification ... When conducting a survey in a large printing company in Shenzhen, I saw that the company was promoting alcohol-free printing and achieved good results. Using alcohol-free printing can not only reduce printing costs, but also be more environmentally friendly, and can reduce a series of environmental problems caused by alcohol volatilization. So I compiled this article on alcohol-free printing in order to let everyone better understand and apply Alcohol printing. Alcohol-free printing using alcohol substitutes is easier to achieve water-ink balance. Printing with a specific thickness of ink film that has not been diluted with alcohol can produce higher quality prints with fine dots and less emulsification. 1. Alcohol substitutes Alcohol substitutes differ from IPA (isopropyl alcohol) in several key properties, including their viscosity, surface tension, pH, and fountain solution conductivity. Alcohol-free products cannot be applied to different printing machines at will, which requires close communication with printing operators to seek the best fountain solution formula from suppliers. In fact, there are many alternatives to alcohol that can be used. They are composed of one or more chemicals extracted from the chemical family of glycol and glycol ether, and some other additives similar to IPA are added. And these formulas are trying to completely replace the IPA in the fountain solution, and provide some unique properties. More importantly, the concentration of alcohol substitutes we use is much lower than that of IPA. Under the same printing conditions, a small amount of alcohol substitutes can achieve 10 to 20 times the effect of IPA fountain solution. 2. Viscosity of fountain solution Adding IPA to the fountain solution will greatly increase its viscosity, but many alcohol substitutes have little or no effect on viscosity. Due to the reduced viscosity of alcohol substitutes, less fountain solution is measured by squeezing or using a measuring roller on a continuous contact dampening roller, which must increase the dampening roller speed, leading many printing operators to erroneously conclude that More water must be used when printing with alcohol substitute fountain solution. In fact, the solution to increase the viscosity to a certain extent is to cool the fountain solution. 3. Surface tension The ability to quickly wet the printing plate and form a thin water film are the two key requirements of offset printing on the fountain solution, which is mainly determined by the surface tension of the fountain solution. It is generally believed that fountain solution with low surface tension can be better used in high-speed printing, but there are reports in Europe that are contrary to this. It is understood that current alcohol substitutes can achieve the low surface tension of IPA used by printing operators. The surface tension of pure water is 72 × 10-3N / m. In the fountain solution, the concentration of alcohol is 10% ～ 25%. Reduce the surface tension to reach (35 ～ 45) × 10-3N / m. The fountain solution quickly forms a continuous film covering the entire printing plate. The alcohol-free fountain solution uses surfactants and solvents to reduce surface tension. Surfactants or surface-active additives are organic chemicals, because of their polar molecular structure, they tend to concentrate on the interface. Normally, they are at the interface between fountain solution and air, and between ink and air. In the case of high-speed printing, these interfaces change rapidly, so the surfactant must quickly spread out to replenish the new interface. A large amount of surfactant in the fountain solution is very important in the printing process, but too much addition will also exacerbate ink emulsification. 4. Printing brightness and gloss Alcohol is a thinner that actively attacks the ink. It makes the ink tarnish and affects the color. To achieve an acceptable color, a thicker ink film is required on the impression cylinder. When used in a suitable concentration, alcohol substitutes do not dilute the ink, and only a small amount of ink and water are needed to obtain acceptable colors, so that the dots will be more accurate, and the tendency of dots to increase will also decrease. [next] 5. Conductivity and pH In printing, it is very important to maintain the consistency and stability of conductivity and pH value. Before printing, the conductivity of the fountain solution should be measured. Any impurities may cause abnormal conductivity, at which time the conductivity of the water should be re-examined. In the printing process, both ink and paper may contaminate the fountain solution, and its conductivity increase is normal. The pH value can be measured while measuring conductivity. The pH value of the acid fountain solution should generally be 4.0 to 5.0. For high-quality printing, it is important to maintain the optimal pH value of the fountain solution used. All acidic fountain solutions have a buffering effect to some extent. If the concentration increases, the conductivity will continue to increase at a linear speed, and the pH value will begin to decrease, and then tend to be flat. Therefore, conductivity can determine the concentration of fountain solution more than pH. If the pH value is too high (above 5.5), the printing plate may become dirty. To keep the printing plate clean, increase the amount of water, which may cause serious emulsification of the ink. If the pH is too low (below 3.5), the printing plate may bloom, the ink emulsifies, the roller peels off, and the ink drying time is extended. 6. Practical application of alcohol substitutes There are 2 goals for using alcohol-free fountain solution. The first is to use safe materials to produce high-quality products; the second is to choose and use non-alcohol products to achieve better results. Depending on the dampening equipment, water, ink, substrates and even live parts, these options will be different. 7. Pre-test alcohol substitutes If the printing machine is replaced with a new fountain solution, it must be inspected and tested in advance. The actual testing of a printing unit may sometimes be better than a laboratory equipped with various measuring equipment. The test should be carried out within the range of measurable tolerances. The best way is to carry out according to the instructions of the equipment. If the tolerance has a certain range, the settings and running performance of the printing process can be recorded in the file starting from the lower limit. When using alcohol substitutes, it is important to establish the best water-ink balance through printing experiments. Tests have shown that the use of alcohol-free materials may require adjustments to past production conditions. However, in order to accurately measure this, the production conditions of the enterprise must be quantified. 8. Mechanical adjustment In particular, when using non-alcoholic fountain solution for printing, the requirements for the tolerance of various parameters are stricter, and any problems concealed by the use of IPA may appear. Therefore, if you want to use alcohol-free printing, it is recommended to reduce the amount of alcohol used by about 8%. If this adjustment will cause problems, then once you switch to alcohol-free printing, the problem is likely to be fully exposed. (1) The key to the success of alcohol-free printing is the relationship between the hardness of the test roller and the impression line The main consideration is the measurement roller, which requires a slightly lower hardness than when using alcohol dampening. The measuring roller usually has a hardness of 25 to 30, and sometimes hardens after printing. When using alcohol substitutes, the hardness of the measuring roller is reduced to 18-22. Because softer rollers tend to accept more water more easily, their flexibility increases the width of the impression line between the measuring roller and the chrome alloy roller without increasing the pressure, which makes it easier for printing operators to adjust the width. (2) Through adjustment, reduce the width of the embossed line stripes between the chromium alloy roller and the wetting roller When using alcohol dampening, the width of the embossed line stripes is usually 5/16 to 3/8 inches (8 to 10mm), which depends on the diameter of the cylinder. By increasing the width of the embossing line between the chromium alloy roller and the plate cylinder, a thin film of water can be produced, and slippage can be caused between them. The width of the embossing line may be reduced to 1 / when using alcohol substitute 8 to 3/16 inches (3 to 5 mm). If there is not enough sliding, the plate cylinder will drive the chrome alloy roller. In a typical alcohol wetting system, the metering roller and chromium alloy roller are driven by the wetting system, and the plate cylinder is driven by the printing press. If the plate cylinder starts to drive the chromium alloy roller, the cylinder speed increases and the control of the wetting system is lost. If the ink roller exhibits abnormal wetting, the amount of water at the end of the ink roller increases, which can cause splashing or spraying. Too high speed of the ink roller will also cause excessive pressure on the wetting device, which may lead to circuit disconnection and motor damage. Ideally, when using alcohol-free fountain solution, the wetting system should be able to run at the same speed (or slightly higher speed). (3) Adjustment of measuring roller speed The measurement of alcohol-free fountain solution often needs to be performed on dampening rollers with higher rotation speed (when running at high speed, it can cause slippage and improper tolerance control). (4) Consider the skew or bulge of the water roller Water roller bulge often occurs in some printing equipment, when the diameter of the middle of the measuring roller is larger than the diameter of the edge. Some alcohol-free fountain solutions work well on skewed measuring rollers, while other machines require measuring rollers similar to chrome alloy rollers to reduce the pressure in the center of the roller. When the printing plate is moved to a place with a wet center or a dry edge, the measuring roller must be skewed. If there is not enough water in the middle of the printing plate, it should be equipped with a measuring roller similar to the chromium alloy roller. The optimal skew angle should be determined experimentally, as it may vary depending on the alcohol substitute used. A curved foam line is formed on the edge of the printing plate, which is a good expression of water and ink balance. After the printing machine is stable, the foam line can be verified by shutting down. Ideally, the water-ink balance will produce very shallow, uniform foam lines across the width of the plate. If the printing plate is too dry, the foam line width increases; if it is too wet, the foam line will disappear. [next] 9. Maintain proper concentration Over time, most alcohol substitutes will slowly evaporate from the wetting system, which may increase the concentration of the substitute to a certain extent and cause some problems such as water-ink balance, ink layer and even coating adhesion . Since there is currently no simple method to determine the concentration of substitutes, the system should be updated at least once a week. 10. The key to the successful implementation of alcohol-free printing (1) Give a fountain solution sample to the fountain solution manufacturer for analysis, in order to select the fountain solution and alcohol substitute correctly according to the characteristics of the dampening system and fountain solution used. (2) Discuss and determine the issues of printing production with fountain solution, ink and other suppliers, including printing pressure mode, wetting system, inking system, cylinder cleaning, blanket cleaning and paper type, etc., to ensure that they are completely compatible. (3) Check the pressure setting of the dampening roller and the reading of the hardness tester, including the ink roller and dampening roller, and ensure that the pressure setting between the plate cylinder and the rubber cylinder is appropriate. (4) Follow the manufacturer's comprehensive instructions. If the instructions recommend mixing 3 to 8 ounces / gallon of water, you need to start with the lowest 3 ounces, using pH, conductivity readings, and recorded information as a reference starting point. (5) Run this mixed wetting system, and monitor its printing suitability and operating conditions, including how to roll up the printing plate, how to start printing after the roller of the paper feed device is detached, without excessive fountain solution supply, Whether the printing plate can be cleaned automatically, and feed back relevant information to the fountain solution manufacturer. (6) Periodically check the fountain solution. Paper coating, ink spillage, blankets and roller cleaner may contaminate the fountain solution. Record the temperature, pH and conductivity readings every 3 hours during the printing process. From these printed diaries, find the solution mix that maintains the best working condition. (7) During the printing process, observe the changes in pH and conductivity. When they reach a certain point, printing problems begin to appear, such as paste, dirty, then the fountain solution may be contaminated, at this time to record these problems in the printing log. (8) Drain and clean the wetting system once a week. (9) Regularly allow professional maintenance personnel with qualified technology to check the water circulation system with the wetting system. Cake Tools,Cake Tool Set,Cake Tools and Equipment,Cake Baking Tool,Cake Decorating Tool Yangjiang Ronghong Houseware Co.,Ltd , https://www.rhhouseware.com