This study presents new methods for enhancing Fourier transform infrared spectroscopy (FTIR) measurements to analyse the OH absorbance of anisotropic minerals. With new hardware and software solutions, large numbers of angle-resolved polarised spectra between 0 to 180° can be acquired, processed, and visualised. This allows us to identify spectral endmembers in the Si–O overtone region that can be used to find groups of mutually perpendicular spectra reducing uncertainty of H₂O quantification.