Thermal convection in the presence of a first-order phase change

We report experimental results for convection in a thin horizontal layer of a fluid which is heated from below and which undergoes a first-order phase change. For some parameter ranges the denser layer may be stably stratified above the lighter one, as predicted by Busse and Schubert. Over various parameter ranges we observed hexagonal, inverted-hexagonal, and roll flow. Interesting interactions between two-phase convection and Rayleigh-B\'enard convection are observed near two codimension-two points.