Pass Order Decides Which Effects Remain Achievable
Pass order determines surface energy, registration accuracy, recyclability, and unit scrap rates across multi-step print converting runs.
Set-off
Print Surface Contamination
Physical transfer of uncured or undried ink, varnish, or coating material from the printed front face of a substrate onto the reverse side of the adjacent sheet or web wrap occurs under pressure. In sheet-fed offset, gravure, and flexographic printing, set-off generates unwanted ghost images, ink smearing, and reverse-side marking in the delivery pile or rewound roll. The problem arises when delivery pile stacking weights, web rewinding tension, slow ink setting rates, or inadequate anti-set-off spray powder allow wet ink films to contact adjacent raw surfaces.
Porous paperboards absorb ink oils to accelerate setting, whereas dense coated grades and non-absorbent synthetic films rely on rapid oxidation, radiation curing, or high heat to prevent surface transfer. Quality protocols check delivery stacks at regular intervals to detect ink offsetting before ink oxidation binds stacked sheets together.
Transfer Mechanism Factors
Sheet-fed offset presses deposit wet ink films that require an initial physical setting phase, during which low-viscosity hydrocarbon or vegetable oils penetrate the paperboard coating layer. Delivery stacker units pile hundreds of printed sheets, generating high compressive loads at the bottom of the pallet that press adjacent sheets together. When ink setting proceeds too slowly, or when operators apply insufficient anti-set-off starch powder, the ink vehicle sticks to the unprinted reverse side of the overlying sheet.
In roll-to-roll converting lines, excessive rewind tension squeezes moving web layers together before drying systems fully evaporate residual solvent carriers or water. Blocked sheets tear fibers upon separation, ruining surface integrity and making carton feeding impossible on downstream folding-gluing machinery.
Defect Distinction Boundary
Static electric cling between dry sheets that impairs feeder operations without any wet ink transfer does not constitute ink offsetting. Ink strike-through, where ink vehicles penetrate entirely through the paperboard cross-section to become visible on the reverse side, represents substrate porosity failure rather than surface-to-surface mechanical transfer. Chemical migration of volatile low-molecular-weight substances through cured packaging layers over time belongs to extraction migration categories.
Scuffing and abrasion occurring during pallet transport represent physical friction damage rather than wet delivery-pile transfer. The defect condition ceases once ink films achieve complete chemical crosslinking, polymerization, or oxidative drying.