From Paper-mill to PressroomWheelwright, William Bond
Philosophy
From Paper-mill to Pressroom
Wheelwright, William Bond
Papermaking
MAKE-READY.--Finally, the make-ready should be intelligently varied
according to the subject and the paper. The best printers agree
that different papers to some extent require individual treatment.
A make-ready suitable for a coated paper is not necessarily equally
satisfactory for an uncoated half-tone paper or even a dull-finished
coated stock. But it is not within my province to go further than to
emphasize these warnings.
GRAIN.--The question of the grain in paper is certainly, in many cases,
within the control of the printer when ordering his paper, but its
importance is very frequently overlooked. In machine-made papers there
is a distinct grain that is caused because a majority of the fibers
point in the direction that the stuff flows on the machine, just like
logs floating in a river.
This grain direction is noticeable in folding, the crease being
smoothest with the grain, because folding across the grain encounters
the most resistance and breaks many of the fibers. This is especially
noticeable in fairly heavy book-papers, in bristol boards and
cover-stock, all of which should be scored for folding.
Cut cards, to have the maximum stiffness, should be so trimmed out of
the sheet as to have the grain run in the long direction of the card.
Even in book-papers, where flexibility is desirable, it is necessary
to have the grain run up and down the page. There are occasional
cases when the grain is deliberately arranged to run across the page
to acquire more rigidity. A wide page of light-weight paper might
otherwise be too limp. Moreover, this arrangement makes for stronger
bindings, as the stitches or wires pass around the bundles of fibers
instead of cutting between them. The English books are mostly made up
in this way, but they do not open so easily as when the grain runs
parallel to the binding. Paper is materially weaker across the grain
and can withstand only about half the tensile strain that it could bear
with the grain, although crosswise it is more elastic.
There is one very serious objection to making books or catalogues
“cross-grained.” This is on account of the way fibers are affected
by moisture. The cellulose fiber expands in diameter on absorbing
moisture, for which it has a great affinity. Indeed, a cellulose fiber
is only stable under uniform atmospheric conditions. The expansion of
each fiber in diameter makes paper expand much more across than with
the grain. Obviously, the total expansion of a sheet equals the amount
each fiber expands times the number of fibers that side by side go to
make up the sheet.
When the glue is applied to a book in process of binding, it causes an
expansion of all the moistened fibers.
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