Books were prepared by stacking sheets and holding the assembly at one end with a rigid aluminium clamp. The interleaved books were mounted by their clamps verti cally in a traction instrument(Adamel Lhomargy DY32) The displacement was measured(with an accuracy of 10 pm), along with the total traction force T. Since the experiments explored different ranges of force, three sensors were used with maximum forces of 10 N, 100 N and 1000 N. All the measurements were carried out at ambient humidity, which varied from 30 to 60%. Though humidity affects the friction of paper 126], this effect was negligible as indicated by the reproducibility of the ex- periments(see inset of Fig. 2).