|
CALENDERING (note the
spelling) is a step in the papermaking process that imparts a smooth surface
to the paper. It's done by running the paper through a stack of calendering
rolls--metal cylinders that compress the fibers and reduce the bulk of
the paper. "Supercalendering" produces an ultra-smooth, ultra- thin surfaced
paper that can be used to print skinny books that have a lot of pages.
The trade-offs are loss of opacity and decreased durability.
BASIS
WEIGHT is the weight in pounds of a ream (500 sheets) in the basic size
for that grade. Example: Basis 70 means that a 500-sheet stack of 25x38"
book paper weighs 70 pounds. The basic size is not the same for all grades--each
category has a size used to compute its basis weights.
The
basic size for text, coated, and uncoated papers--in other words, for
the papers most widely used in publishing--is 25x38". Understanding basis
weight is important because mills and paper merchants sell paper by the
pound, not by the number of sheets or the length of the web.
CALIPER
is the measurement of a paper's thickness, expressed as a point size in
thousands of an inch. One point equals 1/1000 of an inch. A 7pt. stock
is .007" thick. (A caliper "point" is not the same as a typeface "point,"
which is 1/72 of an inch--about 14 times as large.) The smaller the caliper,
the more pages per inch (ppi), and vice versa.
Caliper
is not related to basis weight. Two papers of the same basis weight may
be of different thicknesses. That is why we use the term:
BULK
to refer to a paper's thickness relative to its basis weight. For example,
an uncoated paper might be said to "bulk" higher than coated paper.
RETURN TO FAST ACCESS MENU
RETURN TO SESSION OUTLINE
|