  We study the coefficients of the expansion $F(R) = 1/3 c_3 R^3 + 1/2 c_2 R^2
+ c_1 R$ of the free energy of spherical bubbles at $T=T_c$ in pure glue QCD
using lattice Monte Carlo techniques. The coefficient $c_3$ vanishes at $T=T_c$
and our results suggest that the sign and the order of magnitude of $c_1$ is in
agreement with the value $c_1=\pm 32\pi T_c^2/9$ (- for hadronic bubbles in
quark phase, + for quark bubbles in hadronic phase) computed by Mardor and
Svetitsky from the MIT bag model. The parameter $c_2$ is small in agreement
with earlier determinations.
