Measured with a dead-weight micrometer that clamps the sheet between flat anvils at a defined pressure, caliper is reported in micrometers or in thousandths of an inch, which board makers call points. It sets bulk, stiffness and how a stack feeds and folds. Calendering trades caliper for smoothness and gloss, and caliper loss usually costs opacity at the same time.
Caliper is down 4 microns since the calender load change, and the folding customer will notice.
Also heard as
- thickness
- sheet thickness
Related terms
Bulk
Volume per unit mass of paper, the inverse of density, usually given in cubic centimeters per gram.
Grammage
Mass of paper per unit area in grams per square meter, the base for most optical calculations.
Calender
Stack of hard rolls that presses a paper web to make it smoother, glossier and more even in thickness.