Scrunch time: The peculiar physics of crumpled paper - physics-math - 05 January 2012 - New Scientist: No matter how tightly you crumple paper into a ball, you'll be hard-pressed to come up with a structure composed of less than about 90 per cent air. "It's technically possible to compress them further," says Cambou, "but that will take a lot more force because the crumpled sheet increasingly opposes the external force as it's crushed." Menon and Cambou wanted to know why.
Despite their insubstantial constitution, wadded paper balls are capable of feats of considerable strength. They are the ultimate packing material, for instance, able to support and cushion objects far heavier than themselves.