Calendering
Also: calender, calendering, supercalender
A finishing step where the sheet passes through pressurized roll nips to smooth the surface and control caliper.
Calendering presses the paper between hard, polished rolls to compress surface fibers and smooth the sheet. A modern on-machine calender has 1 to 4 nips of hard-to-soft roll combinations. A supercalender is an off-machine unit with up to 12 nips that delivers the very high smoothness SC paper and high-gloss coated grades need.
Every calendering nip reduces caliper, so grammage and stiffness trade against smoothness. Specs balance bulk and surface finish based on end use.
Related
- Smoothness. The surface regularity of a paper, measured by air leak under a pressurized head (Parker Print Surf, Bendtsen).
- Bulk. The volume per unit mass of a paper, calculated as caliper divided by grammage, reported in cm³/g.