Water in contact with extended hydrophobic surfaces: Direct evidence of weak dewetting

X-ray reflectivity measurements reveal a significant dewetting of a large hydrophobic paraffin surface floating on water. The dewetting phenomenon extends less than 15 Angstrom into the bulk water phase and results in an integrated density deficit of about one water molecule per 25-30 Angstrom(2) of water in contact with the paraffin surface. The results are supported by molecular dynamics simulations and related to the hydrophobic effect.