Dissolving interfaces in the presence of gravity

Dynamic surface light scattering from dissolving interfaces in binary mixtures of tunable density contrast shows that the surface tension of the interface between the upper and lower phases of the mixture dissolves more slowly for a mixture of higher density contrast. Even for a lower density contrast mixture, the dissolution is still slower than would be expected from naive application of equilibrium diffusion arguments. The factor most likely to be responsible for this anomalous dissolution is gravity, through a mechanism based on the competition between diffusion and sedimentation across the interface.