  We study spherically symmetric bubble growth and droplet decay in first order
cosmological phase transitions, using a numerical code including both the
complete hydrodynamics of the problem and a phenomenological model for the
microscopic entropy producing mechanism at the phase transition surface. The
small-scale effects of finite wall width and surface tension are thus
consistently incorporated. We verify the existence of the different
hydrodynamical growth modes proposed recently and investigate the problem of a
decaying quark droplet in the QCD phase transition. We find that the decaying
droplet leaves behind no rarefaction wave, so that any baryon number
inhomogeneity generated previously should survive the decay.
