Printing balance of offset fountain solution (top)

Lithography is the use of oil-water immiscible properties to keep the fountain solution and ink on the surface of the printing plate relatively balanced during the printing process to achieve good manuscripts

copy. In actual production operations, the quality of personnel, processes, equipment, raw and auxiliary materials, ambient temperature and humidity and other factors will affect the balance of printing.

The printing balance of the fountain solution mainly includes the balance between the fountain solution and the ink in the printing state (the state of movement), the balance between the printing plate in the working state and the balance of the printing paper under the printing effect.

1 fountain solution

The fountain solution is an aqueous solution prepared by adding certain chemical components in water for wetting the printing plate during offset printing.

1) Purpose of using fountain solution

There are three purposes for using lithographic printing solutions:

1 Form a water repellent film on the blank part of the printing plate to resist the infiltration of the ink on the graphic part to the blank part and prevent the dirty plate.

2 The electrolyte in the fountain solution reacts chemically with the plate that is exposed due to abrasion to form a new hydrophilic layer and maintain the hydrophilicity of the blank part of the printing plate.

3 Adjust the ink temperature. The viscosity of a typical ink changes rapidly with small changes in temperature.

Experiments show that the temperature rises from 25°C to 35°C. The viscosity of the oil drops from 50 Pa•s to 25 Pa•s, and the fluidity of the ink doubles. This will inevitably cause serious spreading of the ink.

2) Common fountain solution

The fountain solution is generally divided into ordinary fountain solution, sprinkling fountain solution, and non-ionic surfactant fountain solution.

Common chemical components added by the dampening solution include inorganic compounds such as phosphoric acid, phosphate, and nitrate, which have high surface tension, poor wettability, low cost, and easy operation.

Ethanol, isopropyl alcohol or other alcohols are added to the alcohol fountain solution, which has the characteristics of low surface tension and good wettability. It is suitable for lithographic printing machines equipped with an alcohol wetting system.

The non-ionic surfactant fountain solution is a new fountain solution developed in recent years. It is generally formulated by adding a non-ionic surfactant to a fountain solution containing other electrolytes. Non-ionic surfactants often use polyoxyethylene, polyoxypropylene ether, alkyl alcohol amides and the like. With the characteristics of low surface tension, good wettability, and stable chemical properties, it is an ideal fountain solution for high-speed multi-color lithographic printing presses.

2 balance between fountain solution and ink

Offset is the use of oil and water immiscible with each other for ink transfer. Theoretically, only when there is a strict boundary between the water film on the surface of the blank part of the printing plate and the ink film on the surface of the graphic part of the printing plate, the ink and ink will not wet each other, ie the ink and water balance will be achieved. However, the printing plate, the watering roller, and the ink roller transfer water and ink during high rolling and mutual rolling. The above ideal static balance is difficult to achieve in the dynamic printing process. (To be continued)