Many powders rapidly spread radially outwards when introduced at an air-water interface. Our prior findings suggest that a surfactant-driven mechanism contributes to this type of particle dispersion [1], where impurities and surfactants, such as oil in seeds, are common in many powders. 

In our experiments, we remove the impurities and surfactants and find the cleaning becomes significant. Notably, the addition or elimination of water rinsing in the cleaning process can either activate or deactivate this rapid spreading behavior. Complemented by Fourier-transform infrared spectroscopy (FTIR) measurements, our results suggest that the presence of water on the silica surface plays an important role in changing particle dispersion behavior at the air-water interface.