page flex test
A binding endurance test designed to determine the
number of times a leaf of a bound book can be
flexed under light tension before it becomes
detached from the book. The book is placed open on
a flat plate, with both covers flat on the
surface. A single leaf is selected and held in a
vertical position, while the remaining leaves on
either side are clamped down. The vertical leaf is
passed between two bars approximately 3/16 inch in
diameter, 1/4 inch apart, and longer than the
leaf, and positioned at a fixed distance of 2
inches above the gutter of the book. A clamp is
attached to the leaf to hold it in a vertical
position, as well as to exert an upward force of 3
to 5 pounds. The bars on either side of the leaf
are moved back and forth a distance of 3 1/2
inches, causing the leaf to flex at an angle of
45° to either side of the vertical, or a
total of 90°. The flexing is at the rate
of 88 per minute, and the test continues until
failure of the leaf, or a maximum of 1,000 flexes.
To accelerate the test, the upward force exerted
on the leaf can be increased.
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