n.a measure of a material’s strength based on its ability to sustain folding until it breaksPoole 1976, 158Further, we have aged a variety of papers, both those which have been deacidified and buffered and those without treatment, for similar periods of time. In the case of newsprint, folding endurance of the encapsulation was inexcess of 6500 folds.Roberts and Etherington 1982The 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.
With the onset of defined international preservation standards, folding endurance has been measured by the number of double folds [ISO 5626: Paper – Determination of folding endurance; TAPPI Test Method T 511: Folding endurance of paper (MIT tester); and TAPPI Test Method T 423: Folding endurance of paper (Schopper type tester)]. Before these standards some nonstandardized techniques measured single folds.