Frost heave in helium & other substances

A thermomolecular pressure associated with a thermal gradient produces the phenomenon known as frost heave in moisturecontaining frozen ground. Thermomolecular pressures can occur in any material. The basic requirement is a perturbed region of phase equilibrium extending to temperatures below the bulk phase boundary, such as the liquid film at an interface undergoing surface melting. Two materials that have exhibited thermomolecular pressure effects to date are ice in various porous media andHe ⁴ in Vycor glass. Thermomolecular pressures and their dynamical effects offer a unique way of studying quantum and classical liquids at interfaces.