The process of folding flat printed sheets into
sections. The number of leaves in a single folded
sheet is always a multiple of two: 4, 8, 16, 32,
and 64 leaves, giving 8, 16, 32, 64, and 128 pages
respectively. Sections with 6, 12, 18 etc., leaves
may be obtained by the use of other than standard
types of folding, or by the use of more than one
sheet, e.g., an envelope fold followed by a right
angle fold will give 6 leaves (12 pages), or a
full sheet folded three times, plus a half sheet
folded twice and insetted within the full sheet
will give a section of 12 leaves (24 pages).
Although a single sheet of paper can be folded
nine times, in bookwork it is unusual to find a
sheet folded more than four times, and most sheets
are slit or perforated if they are to be folded at
right angles more than twice, so as to reduce
wrinkling and buckling.
The principal folds are the parallel (or buckle)
and right angle, with the latter being the most
commonly used fold in bookwork. The parallel fold
is generally used for very narrow books, or for
those that are printed TWO UP .
The third most commonly used fold, though used far
less than either of the preceding, is the
concertina fold, which is used for maps and
folders, as well as for some book sections.
Almost all folding today is done by machine;
however, in the early days of the folding machine,
the work was so inaccurate that good folding could
be done only by hand.
Folding is done "to the paper" or "to the print,"
i.e., register. See also: FOLD TO PAPER ;FOLD TO PRINT ;FOLDING MACHINES ;IMPOSITION ;REGISTER (4) .
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