Flow and torsional oscillator measurements on liquid helium in restricted geometries under pressure

When a solid surface is in contact with liquid helium, the strong van der Waals forces between helium and the solid substrate result in a layer of high-density helium localized on the substrate. It was expected that, upon raising the pressure, further solid layers would grow out from the wall. Many experiments have now shown that this usually does not occur, and even at solidification pressures ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ liquid, rather than solid, wets a disordered surface. This implies that, in the neighborhood of some solid surfaces, liquid helium can exist at pressures above bulk solidification pressure.