warping
The distortion of the covers of a book subsequent
to binding, to the extent that the covers do not
lie flat against the text block. This distortion
is caused by the difference in expansion and
contraction of the various components of the
cover-cloth, boards board paper, and, to a lesser
extent, the films of adhesive which secure these
components together. Warping is found to occur in
the direction of: 1) the side of the material
which has the greater stretch; 2) the side of the
material with the least moisture content; and 3)
the side which is lined or has the greater number
of layers. On newly bound books these factors are
at work because of the setting and drying of the
adhesives; subsequent to binding, stresses may
occur because of atmospheric changes. The
practical means of minimizing warping include the
use of well-matured boards, cutting the boards and
board papers so that the grain (machine direction)
runs parallel to the spine of the book, the use of
adhesives containing a minimum amount of water
(and no more than the minimum amount required of
plasticizer), and adequate pressing of the books
after casing-in or covering. In addition,
maintenance of a stable atmospheric environment is
important.
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