  For the first order transition of the Ising model below $T_c$, Isakov has
proven that the free energy possesses an essential singularity in the applied
field. Such a singularity in the control parameter, anticipated by condensation
theory, is believed to be a generic feature of first order transitions, but too
weak to be observable. We study these issues for the temperature driven
transition of the $q$ states 2D Potts model at $q>q_c=4$. Adapting the droplet
model to this case, we relate its parameters to the critical properties at
$q_c$ and confront the free energy to the many informations brought by previous
works. The essential singularity predicted at the transition temperature leads
to observable effects in numerical data. On a finite lattice, a metastability
domain of temperatures is identified, which shrinks to zero in the
thermodynamical limit. ~
