The web runs through one or more nips between steel rolls, or between steel and polymer-covered rolls in a soft calender, which flattens surface fibers and levels caliper. Calendering raises smoothness and gloss but compresses the sheet, cutting bulk, opacity and often brightness. Too much load or moisture in the nip leads to calender blackening.
Calender load went up to rescue smoothness and opacity dropped a point and a half, same as last time.
Spelling it calendar in a mill report is the quickest way to mark yourself as an outsider.
Also heard as
- calender stack
Related terms
Supercalender
Off-machine stack of alternating steel and resilient filled rolls that gives paper high gloss and smoothness.
Calender blackening
Dark, translucent spots or streaks produced when calendering crushes a sheet that is too wet or under too much nip load.
Bulk
Volume per unit mass of paper, the inverse of density, usually given in cubic centimeters per gram.
Smoothness
How flat a paper surface is at a fine scale, usually measured by air leaking between the sheet and a reference land.