Specifies the methods for the determination of folding endurance of paper using Köhler-Molin, Lhomargy, MIT and Schopper testers. The principle of the methods is folding backwards and forwards in a standardized manner of a narrow strip of paper subjected to a longitudinal stress, until it breaks. The Köhler-Molin, Lhomargy and Schopper methods are applicable to paper of thicknesses up to 0,25 mm thick and having a tensile strength greater than 1,33 kN/m. The MIT tester has interchangeable folding heads allowing a range of thicknesses up to 1,25 mm.