Reconciliation Methods for Yield Loss and Moisture Distortion in Reclaimed Paper Ledgers
Reconciling reclaimed paper ledgers requires converting scale intake weights to bone-dry fiber mass using core probe testing per ISO 287.
TAPPI T 233
Fibre Fractionation
Fibre fractionation tests classify pulp suspensions by fiber length using a series of mesh screens to assess the structural strength of paperboard sheets. Under the standard test method tappi t 233, a wet pulp sample is washed through a cascade of increasingly fine wire screens to separate the fibers into distinct length groups. This classification governs the physical properties of the paperboard, predicting how well the pulp will bind together on the forming wire.
It applies to all papermaking pulps, providing a mechanical profile of the fiber length distribution before the stock is refined and pumped to the headbox.
Fractionation Mechanism
A dilute slurry of pulp is introduced into the first compartment of the tester, where a constant flow of water washes the fibers against a rotating mesh screen. Long fibers are retained on the first screen, while shorter fibers pass through to the next compartment, which has a finer screen. This process is repeated across four or five separate stages, leaving a distinct fraction of the pulp on each screen.
The retained fibers are then collected, dried, and weighed to calculate the percentage of long, medium, and short fibers in the pulp. This profile is essential for mills because long softwood fibers provide the tear strength needed for carton scores, while short hardwood fibers provide the surface smoothness needed for fine printing.
Stiffness Optimization
Sourcing the correct balance of long and short fibers allows mills to produce strong but printable boards. This testing helps papermakers optimize their refining processes to avoid over-beating the pulp, which can shorten the fibers and reduce the stiffness of the folding carton stock. In doing so, it ensures that finished boxes can withstand stacking and transport loads.