Paper Grades and Board Types a Buyer Chooses Between
Matching substrate furnish and bulk to press stress secures structural integrity, optimizes print quality, and minimizes total landed packaging cost.
IGT Pick Resistance
Surface Boundary
Controlled surface cohesion defines the mechanical strength required by a paper grade to withstand the rapid separation forces exerted by printing inks without suffering fiber lift or coating delamination. During offset lithography, tacky vehicle formulations pull against the substrate continuously, demanding that IGT pick resistance exceeds the hydrodynamic viscosity forces of the applied fluid. The physical threshold separating acceptable run speeds from catastrophic stock failure depends on binder distribution within the top sheet.
Papermakers measure this property using pendulum driven instruments that accelerate a printing disc across a test strip under increasing velocity until detachment occurs. Converting plants rely on these threshold values to schedule high speed multicolor jobs without risking blanket contamination or surface picking defects. Lower grades tolerate gentle dampening solutions, whereas premium folding boxboards demand high internal bonding networks to endure heavy pigment loads.
Stress Tolerance
Press operating speeds dictate how much mechanical load the upper layer absorbs during image transfer. Higher cylinder velocities increase hydrodynamic drag inside the ink nip, transforming fluid viscosity into a destructive peeling vector. Starch distribution across the wire side determines whether the structure retains integrity under such duress.
Calendering pressure alters porosity, which changes how deeply synthetic latices penetrate the sheet during coating application. Mills adjust refining intensity to optimize inter fiber bonding, preventing premature delamination when lithographic inks hit the paper at high production rates.
Failure Mode
Complete surface rupture occurs when local tension surpasses internal fiber cohesion. Uncoated stocks lose integrity when individual fibers pull free from the formation, leaving unsightly voids in solid print areas. Coated sheets experience picking when the adhesive binding the pigment particles to the base paper fails under shear stress.
Printers adjust ink tack with varnish additives to mitigate these risks when running borderline substrates on legacy presses. Substrate manufacturers guarantee specific velocity limits based on standardized print tests, ensuring converters avoid costly downtime during commercial production runs.