Origin of stratification in creaming emulsions

Colloidal suspensions aging under gravity have long been known to spontaneously separate into layers. We demonstrate through flow visualization experiments that a lateral temperature gradient as small as 10 mK/cm can be responsible for such stratification and that strata correspond to a stack of convection rolls. A linear stability analysis suggests that the onset of stratification results from a convective instability peculiar to fluids with inhomogeneous mass densities subjected to lateral thermal gradients.