Effect and Influence of Alcohol Fountain Solution on Offset Printing

In 1904, American American Rubel invented the offset printing technology. Afterwards, German American Caspar Hermann brought this technology back to Germany and invented the first three-push offset press in 1906-1907. As we all know, offset printing is based on the principle of ink-water balance, the use of graphic and text parts of the oil and water, and the non-graphical part of the principle of water-repelling and oil-repelling. The graphic on the plate is transferred to the blanket and transferred to the substrate. Indirect printing.

The water mentioned here is not normal water, and it is a fountain solution composed of a buffering agent, a wetting agent, a plate protecting agent and other auxiliary agents. The main function of the fountain solution in the offset printing process is to adjust the hydrophilicity of the hydrophilic surface of the plate surface to form a water film. It has a low surface tension, so that the moisture is assisted in the non-graphic surface, and the dampening The electrolyte in the liquid will react chemically with the metal of the printing plate, and can supplement the damaged hydrophilic layer to produce inorganic salts so that the water film adheres tightly to the blank part of the printing plate, preventing the ink from spreading to these parts. Only a clear dividing line exists between the non-image part of the printing plate and the ink film of the graphic part to realize the water-ink balance of the offset printing.

Due to the influence of paper, paper dust, and other dirt, each time printing is run, the paper puts the blanket's water and ink on it while leaving some weak alkaline dirt on the blanket. If it is not cleaned in time, the diazonium compound of the oleophilic layer will fall off, the dots will be lost, and the hydrophilic organic salt layer that is not part of the image will be worn out, resulting in printing defects such as dirty on the layout surface. The organic acid in the fountain solution and the weakly alkaline dirt can produce a neutralization effect and protect the graphic part to maintain the lipophilicity. At the same time, the paper wool, paper powder and other dirt on the printing plate can be brushed to reduce the abrasion of the dirt on the printing plate. .

Offset printing is a process in which the printing plate constantly rubs against the ink roller and blanket during high-speed operation, which generates a large amount of heat, lowers the viscosity of the ink, changes the rheology of the ink, and causes the phenomenon of ink pile-up. The fountain solution absorbs this heat, distributes the heat through the water and alcohol in the fountain solution, and thus controls the plateau temperature, which is beneficial to the ink and water balance.

There are many factors that affect the pH and amount of dampening solution. For example, the thickness of the plate, the size of the printing area, the moisture content of the paper, the pH, the ambient temperature and humidity of the production workshop, etc. The machine operator adjusts the pH of the fountain solution according to the specific conditions.

Yin Huabin

Reprinted from: Ke Yin Network