Introduction to the Basic Process Principles of Offset Offset Printing

Offset offset printing is an indirect lithography. Since about 1970, offset printing technology has begun to spread widely, and to a large extent surpasses the previously popular letterpress printing technology. Offset printing technology is now the main printing technology.

In the offset printing process, the graphic portion and the blank portion on the printing plate are almost in the same plane. The graphic part is hydrophobic and water-repellent, while the blank part is hydrophilic and oil-repellent. This effect is caused by the physical properties of the contact surface.

On the surface of the blank part of the printing plate, the dampening system coats a thin layer of fountain solution. The fountain solution (water and additives) is distributed on the surface of the blank part. To obtain a good dampening effect, additives must be added to the fountain solution to reduce the surface tension of the fountain solution. However, excessively reducing the surface tension of the fountain solution will cause excessive emulsification of the printing ink and the fountain solution, which will result in the intricate separation of the graphic part and the blank part on the printing plate when the ink is applied.

The ideal offset printing process is based on the physicochemical properties of the various materials and components associated with the process. The most important physicochemical properties include printing plates, ink rollers, blankets, inks, fountain solutions, substrates, and printing presses. Therefore, offset printing technology must be treated as a multi-parameter system, and any change in any one of these parameters will directly affect the printing process.

Source: 21st Century Fine Chemicals Network