The Fundamentals of Printing

The Fundamentals of Printing
2 min read
01 November 2022

Ink balance, hydrophilic blank part, and ink-friendly graphic part (only refers to offset printing)

Incompatibility between water and oil

The chemical concept of similarity and compatibility states that the molecular structure of water with mild polarity differs from that of non-polar oil molecules, resulting in the inability to attract and dissolve water and oil. The presence of this rule results in a flat printing plate. It became able to discern between text and blanks by utilizing water.

Adsorption on the surface

It can adsorb various substances depending on surface tension, allowing for the separation of pictures and texts in lithographic offset printing.

Dot configuration

Because offset printing plates are flat, it is impossible to rely on ink thickness to express the layers of graphics on the printed matter. Rich image layers are produced.

We have such common sense in life: a moist surface is not easily contaminated by oil, and water and oil always oppose one another. Because the offset printing plates are practically on the same plane, a method for successfully distinguishing the blank and graphic parts is required. The "water and oil incompatibility" principle governs the usage of water in offset printing. During the printing process, a thin layer of water is uniformly coated on the surface of the printing plate (in fact, the graphic section will not be wetted by water due to the selective adsorption of the surface of the printing plate), and then coated on the printing plate. The blank section is properly protected when ink is applied.

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zheng yimin 2
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