n. ~ A test of the strength and durability of a planar material, usually paper.
†(Roberts and Etherington 1982) The number of folds which a specimen (usually paper) will withstand before failure, under controlled conditions in a specified instrument. In the usual test, a specimen is subjected repeatedly to double folds through a wide angle while under tension. Folding endurance is a very important indication of the durability of archival papers. A decline in folding endurance is the most sensitive indicator of aging and deterioration of paper.