  The effect of buoyant forces on viscous coarsening is studied numerically. It
is shown that at any time buoyant forces induce a vertical flow that scales
like the Stokes velocity. This does no induce any noticeable change in the
morphology of the coarsening microstructure under a value of the characteristic
length of the pattern. Above this threshold the pattern evolves toward a quasi
two D pattern and coarsening stops. The characteristic length is shown to scale
like $\sqrt{\gamma/(g \Delta\rho)}$ where $\gamma$ is he surface tension and
$\Delta\rho$ the mass dnsiy difference between the phases.
