About the use of printing fountain solution and parameters
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
First, the technical parameters of the dampening solution and its detection method
1. pH value
The pH of the dampening solution can not be ignored, and the pH value is too high or too low, which will adversely affect printing. When the pH value is too high, the surface tension of the fountain solution is lowered, and the oleophilic layer of the plate is damaged, so that the ink is severely emulsified, and the ink is unbalanced: the pH value is too low, which affects the oxidative drying speed of the ink. And corrosive plate base, reducing the printing durability of the printing plate. It is generally believed that the most reasonable pH value of the Ps version should be maintained at 4.8 to 5.3, at which time the ink balance is most easily controlled and the printing quality is good. Simple test of the pH of the dampening solution in the printing shop can be done with a pen pH meter. The accuracy is soil 0.1, and the measuring head is rinsed with water before measurement. Neutral (pH 7.0) correction was performed. The dampening solution should be taken out of the sink during the measurement and measured after standing. The instrument reads the number after it is stable.
2. Conductivity
Usually, the automatic control system of the offset printing press can automatically add or reduce the dampening solution according to the preset conductivity to control the amount of dampening solution. therefore. Whether the conductivity value setting is appropriate or not. It directly affects whether the amount of dampening solution added in the printing is appropriate. In turn, it affects ink balance and print quality. Different brands of dampening fluids have different compositions and their electrical conductivity is different. In addition, the conductivity is also affected by water quality and temperature, so the setting of the conductivity of the dampening solution should be determined according to the actual conditions of different brands and local water quality. The conductivity of the test dampening solution can be measured using a pen-type conductivity meter, which is also cleaned and calibrated with water before testing. It should be noted that the conductivity value is the value of the reaction dampening solution concentration, and the value measured by the conductivity meter can indirectly determine whether the concentration of the dampening solution is appropriate.
3. Alcohol (isopropanol) concentration
It is customary in the industry to use an isopropyl alcohol-containing fountain solution as an alcohol fountain solution. Alcohol acts as a wetting agent, which increases the viscosity of the fountain solution while reducing the surface tension of the water. The amount of traditional dampening solution alcohol can often reach about 15%. However, isopropyl alcohol is not environmentally friendly and relatively expensive. Many new fountain solutions already contain a wetting agent, which can greatly reduce the amount of isopropyl alcohol. The test for alcohol concentration can be done using a hydrometer. The German FOGRA Association uses a densitometer to measure the dampening solution during the dampening solution test, and then determines the alcohol concentration based on the density corresponding lookup table. This method is widely recommended by printers and distributors.
4. Surface Tension
A good dampening solution is required to spread in the blank part of the printing plate and has good wettability. The surface tension of the fountain solution is smaller. Its spreading performance on the plate is better. 1. The rough way to measure the surface tension of a dampening solution is to apply a dampening solution to the blank portion of the plate. Use a magnifying glass to see the spread of the dampening solution on the plate. If the dampening solution does not spread out to the surroundings, the surface tension of the dampening solution is too high: if the dampening solution quickly spreads out to the surroundings. This indicates that the dampening solution has good wetting properties on the printing plate.
5. Buffering capacity
The dampening solution is a buffer solution, which means adding a small amount of strong acid or alkali to the dampening solution. Or dilute the dampening solution. The pH of the dampening solution remains essentially unchanged. Since the fountain solution needs to maintain a stable pH, a pH buffer is added to the fountain solution. It is also because the fountain solution has this buffering capacity that its pH does not reflect its concentration. The titrating method can be used to add an indicator to the dampening solution, and the buffering capacity of the dampening solution can be measured by the amount of the dripping liquid when the indicator is discolored.
6. temperature
The temperature of the fountain solution is also a major factor affecting the balance of offset ink. Different temperature dampening solutions under the same printing conditions. The ink balance is different. Increasing the temperature of the fountain solution will increase the emulsification of the ink, and vice versa. As the temperature increases, the amount of dampening solution will also increase. The temperature in the printing shop will cause changes in the temperature of the fountain solution. Therefore, the workshop should pay attention to the adjustment of room temperature. In the summer. Some printing shops reduce the temperature of the fountain solution by adding dampening solution ice to the water bucket to prevent excessive emulsification of the ink. The temperature test can be done using a thermometer.
Second, the use of dampening solution
1, the choice of dampening solution
Because the role of dampening solution in lithographic offset printing is quite critical. Therefore, how to choose the right dampening solution is particularly important. There are many kinds of dampening solutions on the market, which can be divided into alcohol dampening solution (alcohol-containing dampening solution), non-alcohol dampening solution (ordinary dampening solution) and surfactant dampening solution. According to the scope of application, it can be divided into fountain paper for high-speed rotary offset printing machine, dampening solution for commercial high-speed rotary offset printing machine and dampening solution for single-sheet lithographic offset printing. For the printing company, from the practical point of view combined with the specific production situation of the company to choose the most suitable fountain solution.
2. Runner solution usage control
The general control principle of the amount of dampening solution is to minimize the amount of dampening solution used on the premise that the printing plate is not dirty. The amount of dampening solution used varies under different printing conditions. Mainly from the following aspects:
(1) paper paper has a high water content and a small amount of dampening solution; conversely, the paper has a low water content. The amount of dampening solution is large. Simultaneously. When the surface strength of the paper is low, an appropriate increase in the amount of dampening solution can reduce the problem of soiling caused by paper falling off and falling hair.
(2) Ink For the ink that is difficult to emulsify, it is necessary to appropriately increase the concentration of the fountain solution.
(3) plates: CTP version and PS version have different surface properties. The CTP version requires a thicker dampening fluid film. In addition. The stronger the adsorption of the blank part of the printing plate on the water film, the more dampening solution is needed.
(4) Printed text: The amount of dampening solution used when printing on the ground is obviously larger than that when printing the text and dot pattern.
(5) Printing speed: The amount of dampening solution increases as the printing speed increases.
(6) Ambient temperature: The higher the ambient temperature, the greater the amount of dampening solution.