Films of various surface-active species are found on the surface of water bodies from the sea down to microscopic spray droplets. These films affect the properties of the water droplet and therefore have significant impact on atmospheric chemistry, meteorology, and, ultimately, climate science. Our work looks at films composed of mixtures of surfactants and compares their behaviour to that of pure films. We have very recently found distinct behaviour of single-component films at atmospherically relevant temperature and salinity conditions. For this beamtime we propose to study mixed films at atmospherically relevant temperatures and salinity conditions for the first time.