Capillary Pressure Dynamics and Coating Micro Porosity Structure in Paper
Micro-porous paper coating capillary dimensions govern dynamic ink vehicle filtration rates, ink setting speeds, press energy consumption, and total converted sheet yield.
Heatset Web Offset Blistering
Print Defect
Physical deformation of the paperboard surface during high-temperature ink drying impairs both the visual quality and structural integrity of printed materials. Heatset web offset blistering is the formation of small bubbles or ruptures in the coating layer when moisture trapped in the paperboard vaporizes rapidly in the drying oven. This occurs when the moisture cannot escape through the printed ink or coating layer fast enough.
It is a common challenge in high-speed offset printing where ink coverage is heavy and drying is rapid.
Defect Prevention
Prevention of this failure requires careful control of the paperboard moisture content and printing press temperature. When printing on susceptible grades, heatset web offset blistering can be avoided by maintaining the board’s moisture content below five percent. Low-barrier coating formulations and porous inks also help by allowing the steam to escape without rupturing the surface.
Operators can reduce the oven temperature while extending the drying time to further decrease the risk of defect formation.
Structural Boundary
Heavy ink coverage on both sides of the sheet increases the likelihood of this issue. Multiple layers of ink create an impermeable seal that blocks steam exit routes. Under these conditions, the internal bond strength of the paperboard becomes the primary line of defense.