  We report on the dynamical formation of self-bound quantum droplets in
attractive mixtures of $^{39}$K atoms. Considering the experimental
observations of Semeghini et al., Phys. Rev. Lett. 120, 235301 (2018), we
perform numerical simulations to understand the relevant processes involved in
the formation of a metastable droplet from an out-of-equilibrium mixture. We
first analyze the so-called self-evaporation mechanism, where the droplet
dissipates energy by releasing atoms, and then we consider the effects of
losses due to three-body recombinations and to the balancing of populations in
the mixture. We discuss the importance of these three mechanisms in the
observed droplet dynamics and their implications for future experiments.
