  We study thermal convection in a colloidal glass of Laponite in formation.
Low concentration preparation are submitted to destabilizing vertical
temperature gradient, and present a gradual transition from a turbulent
convective state to a steady conductive state as their viscosity increases. The
time spent under convection is found to depend strongly on sample
concentration, decreasing exponentially with mass fraction of colloidal
particles. Moreover, at fixed concentration, it also depends slightly on the
pattern selected by the Rayleigh B\'{e}nard instability: more rolls maintain
the convection state longer. This behavior can be interpreted with recent
theoretical approaches of soft glassy material rheology.
