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5. Tests

When evaluating a bound volume, initial examinations are primarily non-destructive and visual. The volume, especially a single-copy volume bound for library use, is visually examined to ensure all general requirements as outlined in this document have been met.

Where an obvious problem exists, measurements are taken to determine the degree of error. In some cases, destructive testing may be performed to further document the problem.

5.1 Adhesion

The following are several indicators of the effectiveness of an adhesive.

5.1.1 Rupture

For bookbinding, the major requirement is that, when separated, the surfaces of the materials joined must show evidence of rupture along the entire glued area.

5.1.2 Appearance

The glued area is examined to ensure there is no warping, creasing or unevenness in the materials glued together.

5.1.3 Flex Test

The flex test is performed to evaluate the strength of adhesion of pages to the spine in an adhesive bound volume. This test does not apply to deteriorated material or material over 30 years old.

5.2 Flex Test Method

The flex test is performed at 21°C on samples, which have been conditioned to equilibrium at that temperature.

  • A leaf is flexed with 2.27 kg (5 lbs.) of pull until the leaf separates from the spine or until it withstands 3OO flexes.
  • Each book is tested at a minimum of three places: one quarter, one half and three quarters through the book.
  • The exact page numbers tested and the number of flexes of each leaf are recorded.
  • If a failure occurs in less than 3OO flexes (case hard cover books), or in less than 200 flexes (adhesive soft flexible cover books), the tester is moved 10 pages forward or backward and a re-test are performed.
  • The average of the two lowest flex results determines the defect class: minor, major or critical.
  • A book is assessed "defective" if two critical page failures occur.

Punch perforated slot bound volumes are tested by performing the flex test on the two middle leaves of a signature. If a failure occurs, a re-test is performed on the two middle leaves of the next signature.