  We report on an experimental study of small cluster dynamics during the
coarsening process in driven granular submonolayers of 120mkm bronze particles.
The techniques of electrostatic and vertical mechanical vibration were employed
to excite the granular gas. We measure the scaling exponent for the evaporation
of small clusters during coarsening. It was found that the surface area of
small clusters S vs time t behaves as S ~ (t_0-t)^(2/3) for lower frequencies
and S ~ (t_0-t) for higher frequencies. We argue that the change in the scaling
exponent is related to the transition from three dimensional to two dimensional
character of motion in the granular gas.
