Surface Rupture
The localized tearing or removal of fibers and coating fragments from a paperboard surface occurs when the tensile pull of the printing ink exceeds the surface strength of the substrate. Operators identify this physical failure as surface picking, which creates small white spots on the printed sheet where the bare paperboard is exposed. This defect destroys the visual quality of the graphics and can contaminate the printing press.
Tack Confrontation
High-speed offset presses generate high tensile forces as the paper is pulled away from the ink-covered blanket. When these forces exceed the internal cohesion of the coating or the fiber bond strength, surface picking takes place. The detached particles adhere to the rubber blanket, where they block ink transfer on subsequent sheets and cause compounding print defects.
This problem is aggravated by high ink tack or by a weak fiber network in the paperboard’s top liner.
Press Adjustment
Pressrooms address this issue by adding tack-reducing compounds to the ink or by slowing down the printing press. Mill managers can also improve the surface sizing of the paperboard during manufacture to increase its resistance to picking. This dual approach ensures a clean, continuous print run on high-tack jobs.
