This setup enables the observation of the water nuclear spin isomer conversion using Fourier transform infrared spectroscopy (Nexus 670 FT-IR). In a UHV chamber, a salt window transparent to the infrared (KBr or CaF2) covered with water endofullerenes (H2O@C60) is installed within a sample holder cooled using a closed-cycle helium cryostat. The temperature of the sample holder can be varied between 6K and ambient temperature (Lakeshore 325 controller) in order to follow the conversion kinetics of the confined water nuclear spin isomers.