  The formation rate of quark matter droplets in neutron stars is calculated
from a combination of bubble formation rates in cold degenerate and high
temperature matter. Nuclear matter calculations of the viscosity and thermal
conductivity are applied. Results show that droplets form only in the core of
neutron stars shortly after supernova collapse, where pressures and
temperatures are high, and for sufficiently small interface tension between
nuclear and quark matter. Coulomb energies hinder formation of large droplets
whereas the presence of strange hadrons in nuclear matter increase the droplet
formation rate.
