Matt Lamination Cracking at the Crease against Gloss That Survives
Matt lamination cracks at the crease because silica matting inclusions reduce film elongation capacity, requiring expanded matrix channels to lower folding strain.
Paperboard Grain Direction
Fiber Alignment
Physical orientation of the cellulose fibers in a sheet of paper or board is determined during the formation stage on the paper machine. Paperboard grain direction indicates the axis along which the majority of the fibers lie parallel to the direction of the moving wire. This property greatly influences the stiffness, tearing resistance, tensile strength and dimensional stability of the material.
It is a fundamental consideration for both the printer and the structural designer.
Structural Influence
Board is substantially stiffer when bent across the grain than when bent along it. In carton manufacturing, the grain usually runs around the girth of the box to provide maximum resistance to bulging. Creasing is easier and cleaner when the fold is made parallel to the fibers, while folding across the grain requires more force and is more likely to cause cracking.
Moisture also affects the board unevenly, with the sheet expanding more in the cross direction than in the grain direction. Printers must align the grain to the press cylinders to avoid registration issues caused by paper stretch.
Identification Method
Tearing the board provides a quick way to identify the grain because it will tear in a straighter line parallel to the fibers. Professionals also use a bending test where the sheet is flexed in both directions to see which side offers less resistance.