is, by far, the most important factor in the folding process. Paper choice
is not only for aesthetics, but also for practicality. The wrong paper
choice on a folded piece can produce a disappointing result. For example,
a large-sized brochure printed on thin paper is floppy, and a big, folded
poster printed on thick paper is wrinkled and won't lay flat. Much consideration
and often the advice of your printer or paper representative is required
to make the right choice. It is essential to understand the characteristics
of paper before we can understand how it performs in the folding process.
fibers have certain characteristics that depend upon the nature of the
composition of the fiber and the way in which it is milled. As climate
changes, the fibers can expand and contract considerably in their thickness,
but, in terms of length, they remain virtually unaltered.
The way that
paper fibers are laid down in sheets during manufacturing determines the
certain characteristics of expansion and contraction or grain direction.
These characteristics vary with each of the processes normally used in
the production of paper.
Paper produced by machineryvat machines or long web machineshas a pronounced
grain direction because the fibers align themselves parallel to the direction
of movement on the machine.
The highly diluted pulp of a hand-made paper is evenly spread over a web
through manual shaking which causes the fibers to follow a random orientation.
For this reason, there is no discernible grain direction in hand-made
paper, and the effects of expansion and contraction are virtually identical
in both directions.
Paper, like wood, has a grain direction. Paper is made out of cellulose
fiber material, and the direction in which these fibers line up during
the manufacturing process determines the grain of the paper. With the
grain, there is greater strength, and against the grain there is greater
expansion and contraction which makes it less stable. This strength with
the grain occurs because during the manufacturing process, the fibers
are stretched so that they lose virtually all further capacity for expansion,
which creates relatively good dimensional stability.
A fold is
cleaner and more resilient when the grain is parallel to the fold. A fold
against the grain may not lay as flat, and can cause cracking (a rough
appearance) most noticeable in areas of heavy ink coverage. A fold against
the grain is less resilient, and the pressure exerted by the rollers on
the folding machine must be reduced to avoid an excessive weakening of
the paper along the fold line. If folding against the grain is a must,
a die-score can alleviate some of these problems, as well as careful paper
exercise: Testing the paper grain
Do these exercises with your students to illustrate paper grain. All you
need is a stack of 4 x 6 sheets (or other size) of paper. Distribute three
Fingernail Test" With the fingernails of the thumb and middle
finger, pinch and slide down the vertical and horizontal edges of the
sheet of paper. With the grain, there is virtually no change but, against
the grain, a wave will be clearly visible.
Bending Test" When a square test-sheet is bent in both directions,
there will be less resistance parallel to the grain than against it.
Tearing Test" Tear a sheet on the vertical dimension, then tear
it horizontally. With the grain, the tear will be relatively straight.
Across the grain, there will be greater resistance to tearing, resulting
in a jagged edge