Physical Ratio
Material thickness measurements relative to the unit weight of a paperboard sheet determine the bulk and stiffness of the finished product. Specific volume is the ratio that expresses how much space a given mass of paper occupies, acting as the inverse of density.
Stiffness Control
High bulk means that a sheet is thick for its weight, which directly improves its resistance to bending. Paper mills adjust the refining and pressing steps of the manufacturing process to maintain a high specific volume when producing folding boxboard. A higher volume allows the board to achieve the necessary stiffness while using less raw wood fibre, which reduces both production costs and transport weight.
Converting Benefit
Packaging lines benefit from high-bulk paperboards because they provide the necessary structural strength to protect heavy goods without adding dead weight to the pallet. If the specific volume of the board is too low, the cartons may bulge or collapse when stacked in a warehouse. Using a high-volume board also ensures clean creasing and folding during the box-making process, as the thick, low-density core can deform without fracturing.
This property is particularly valued in high-speed filling lines where boxes are erected, filled and sealed in a fraction of a second.
