In offset printing, the quality of the ink, the quality of the ink adjustment, and the control of the ink are very important to the printing quality, especially the color printing quality. As for fountain solution, its function and role are often not paid enough attention by people.
In some printing houses, sometimes the print quality is not good, everyone generally first suspects whether there is a problem with the printing plate, rather than checking and adjusting the use of fountain solution.
Although the composition of the fountain solution is not complicated, it seems to be water, but to ensure that the blank part maintains good hydrophilicity during printing, and to ensure the balance of water and ink to obtain an ideal printed product, the fountain solution must contain a certain amount of electrolyte, Hydrocolloids and other substances. Must have the following functions and functions: 1. During printing, the fountain solution forms a thin and uniform water film on the blank part of the printing plate. This water film has the function of preventing the ink from spreading to the blank part.
2. The fountain solution continually supplements the hydrophilic layer of the printing surface during printing. Due to the continuous contact and friction between the blanket, roller, water roller, and ink roller and the printing plate, the hydrophilic layer on the surface of the printing plate wears out, which requires The electrolyte in the fountain solution repairs the damaged hydrophilic layer and reforms the new hydrophilic layer to extend the life of the printing plate.
3. The fountain solution can adjust and control the temperature of the printing surface during printing to prevent the machine from overheating and the viscosity of the ink from changing drastically to affect the printing.
4. The fountain solution should have the function of preventing the emulsification of the ink (guaranteeing a certain emulsification value of the ink, which is very important for the good transfer of the ink) to ensure the rapid realization of the water-ink balance.
5. During printing, the fountain solution should also have the function of removing powder, linting, paper scraps, water glue, cotton lint and other debris from ink and printing materials to prevent these debris in the printing plate and blanket Gather on the plate, causing scratching of the printing plate and premature damage to the printing plate. Therefore, the function of fountain solution is very complete, and its role is very important, and it cannot be ignored.
Fountain solution, also known as water bucket liquid, fountain water, water bucket water. The fountain solution can be divided into: alcohol fountain solution (strictly speaking, alcohol-containing fountain solution), alcohol-free fountain solution (common fountain solution) and surfactant fountain solution. According to their different requirements, it can be divided into: fountain solution for high-speed web offset printing presses, fountain solution for commercial printing rotary offset printing presses, and fountain solution for single sheet offset offset presses. In actual use, it is generally not so strict, and it is often chosen by each printing house.
The internal composition of high-quality fountain solution is also more complicated. Usually the fountain solution should be composed of the following types of substances: 1. The water is preferably deionized water or distilled water. If tap water is used, the water quality should not be too hard or too soft.
2. The buffer fountain solution is generally acidic, and the buffer plays a role in stabilizing the pH value in the fountain solution. As the amount of buffer added changes, the pH of the fountain solution will fluctuate to a certain extent. Commonly used sodium dihydrogen phosphate or ammonium dihydrogen phosphate.
3. In the process of offset printing, the fountain solution always keeps in direct contact with the printing plate, and the blank part (inorganic salt layer) of the printing plate will be continuously dissolved, reducing the hydrophilicity of the printing plate, resulting in the printing plate Dirty. The printing plate protector can continuously replenish the dissolved inorganic salt layer to maintain its dynamic balance and ensure the stable hydrophilicity of the printing plate.
The role of fountain solution in printing cannot be ignored. The essence of the plate protector is to use electrolyte.
The electrolyte used for fountain solution is mainly phosphoric acid, chromic acid, nitric acid and other salts. The printing plate protective agent often contains a small amount of protective glue, and the plate will not be dropped if there is a temporary shutdown.
4. In the printing process, the amount of fountain solution should be as small as possible without the dirty version.
The wetting agent is very important. The wetting agent can reduce the surface tension of the fountain solution, so that the moisture is evenly distributed on the printing plate. Adding an appropriate amount of wetting agent can achieve good results with less fountain solution. Glycerin has good hygroscopicity and can play a good wetting effect on the plate.
5. The new type fountain solution of surfactant does not advocate the use of alcohol, but must add a non-ionic surfactant that can reduce the surface tension and not make the ink easy to emulsify, such as polyoxyethylene polyoxypropylene ether (2080 ) And laurate diethanolamide condensate (6501). Carboxymethyl cellulose is an anionic surfactant and can also reduce the surface tension of the solution. There are too many types of surfactants, and users can choose according to their needs.
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