Fast cooling to deep supersaturation for solvent crystallization seems to have two major components. One involves mainly the thermodynamics or phase equilibrium chemical thermodynamics of deep supersaturation. The other component focuses on the fast-cooling or heat-transfer aspect. All previous related crystallization work known to us involves a cooling process coupled with crystallization. This method does the cooling quickly to supersaturated conditions, so the cooling does not couple or interfere with the subsequent isothermal crystallization at supersaturation. Although adiabatic cooling and isothermal crystallization are well-known individually, their combination here with proper choice of liquid and cooling ballast temperatures can achieve supercritical conditions uniquely.