A spatial variation of temperature in the sodium film on the surface of the grazing incidence liquid metal mirror (GILMM) will give rise to convection due to the temperature dependent variation in surface tension. This is called thermal capillary convection or the Marangoni effect and causes the surface to have ripples or waves. This note estimates, the magnitude of this effect and finds, with care, design parameters can be chosen to, make the resulting ripples sufficiently small so that a laser beam can be focused on a target of 1/4 mm spot size at 30 m distance, for example. Smaller spot sizes are discussed.