  We investigate the process of the slow unrolling of a roll of typical
pressure-sensitive adhesive, Scotch tape, under its own weight. Probing the
peeling velocities down to nm/s resolution, which is three orders of magnitudes
lower than earlier measurements, we find that the speed is still non-zero.
Moreover, the velocity is correlated to the relative humidity. A humidity
increase leads to water uptake, making the adhesive weaker and easier to peel.
At very low humidity, the adhesive becomes so stiff that it mainly responds
elastically, leading to a peeling process akin to interfacial fracture. We
provide a quantitative understanding of the peeling velocity in the two
regimes.
