Autoclave foaming using supercritical CO₂ as a blowing agent is a widely used technology for the fabrication of cellular structures. Saturation parameters near the liquid phase of the medium lead to high pressure drop rates and severe cooling of the blowing agent due to various thermodynamic phenomena. The temperature drop during depressurization affects the viscosity of the amorphous polylactide (PLA) used in this work. Analysis of density as a function of saturation temperature and pressure during saturation allows identification of a "valley" bounded by three limits to high expansion rates resulting from pressure-induced cooling and other effects known in the literature. The increased process knowledge enables the production of tailored foams for specific applications.