The wettability of calcium fluoride by liquid Ga and Ge was studied. The initial contact angles indicate that pure liquid Ge and Ga do not wet CaF2. Different spreading kinetics during the experiments was observed. The contact angle in CaF2/Ge system increases with time, while the contact angle in CaF2/Ga system decreases. The same differences were also observed for temperature dependences of the contact angle. It was suggested that these wetting/dewetting tendencies are related to the ratio of the vapor pressure values for the melt and for the substrate. The experimental observations were confirmed by a thermodynamic analysis.