1.1 ,This test method describes the use of the M.I.T.-type folding apparatus for determining folding endurance of paper and plastics film. The M.I.T. tester can be adjusted for samples of any thickness, however, if the outer layers thicker than about 0.25 mm (0.01 in.) rupture during the first few folds, the test loses its significance. The procedure for the Schopper-type apparatus is given in Test Method D643.