What causes uneven ink application?

There are several causes for uneven ink film thickness. From the perspective of the ink itself, improper formulation can result in inconsistent application. Additionally, even if the ink has been prepared correctly, dried ink skins or contaminants can negatively affect the film’s uniformity. Using solvents can cause the screen mesh to swell and soften during the printing process. This swelling can block the mesh openings, typically allowing ink to pass through. Consequently, the ink cannot transfer smoothly, leading to irregular thickness of the ink film.

Several precautions must be taken to prevent issues related to uneven ink film thickness. First, it is important to filter the prepared ink—especially older ink—through a mesh before use to ensure that any dried ink skins or impurities are removed. Additionally, when reusing previously employed screens, all residual ink attached to the screen frame must be thoroughly cleaned. After each printing session, cleaning the screens and related tools, such as squeegees, is crucial to maintaining their condition for future use.

When printing on glass, damage to the sharp edge of the return ink blade can cause streaks in the direction of the blade’s movement, resulting in uneven ink application. To avoid this, the blade’s edge must be well protected and kept free from damage. If any damage occurs, the blade should be carefully polished with a grinding machine to restore a smooth edge.

Furthermore, the evenness of the printing table can significantly affect ink distribution. Uneven surfaces can cause the ink film to vary in thickness, with raised areas producing thinner ink layers and the recessed regions producing thicker ones. This phenomenon is another form of uneven inking. Additionally, dust particles on the back of the glass or the surface of the printing table can also contribute to such defects. Therefore, maintaining a clean, level printing surface and a dust-free environment is essential for achieving consistent ink application.