Paint waste

Ink drop is the designation for the color density variation (unevenly thick ink layer) in the printing direction in offset printing .

The term "paint waste" was chosen because the paint layer thickness at the end of the sheet is usually smaller than at the beginning of the sheet. But this does not have to be the case. The phenomenon of ink loss occurs in inking units that consist of several rollers rolling on top of each other and in which some rollers perform a lateral, mostly sinusoidal distributor movement. The color drop has two causes:

1. The uneven decrease due to the print image: If no color is transferred to the print image (in the plate channel and at color-free print image areas), the average ink layer thickness on the inking unit rollers increases and when color is transferred to the print image (at printing areas) it decreases the average ink layer thickness on the inking unit rollers. This has an effect on the print image and the transferred ink layer thickness in the sense that after passing through the plate channel the inking unit has a higher middle ink layer than after the ink has been transferred to the printed image and therefore the ink layer thickness on the printed sheet is higher than at the beginning of the sheet Arch end.

2. The lateral trituration of the ink rubbers: It can be observed that the lateral movement of the ink rubbers has an influence on the color profile in the running direction of the sheet, namely in the sense that a relatively large amount of ink is transferred with slowly moving sideways and with itself quickly laterally moving grinder relatively little color is transferred. The movement pattern of the distributor rollers is thus impressed on the color profile on the printed sheet.

These two effects result in the color profile in the direction of the sheet. In the worst case, they can add up. On the other hand, the ink profile can be influenced by changing the lateral movement pattern of the distributor rollers (distributor application point) in such a way that they work in opposite directions and thus minimize ink loss.