Stober silica particles having diameters of ca. 100 and ca. 200 nm were prepared and silylated using trimethylsilyl N,N-dimethylcarbamate, achieving a range of surface coverage by trimethylsilyl groups by varying the amounts of silylating agent used. The efficacy of silylation was characterized in terms of hydrophobicity of the particles which was assessed by film balance investigations at water-air interfaces and additionally by imaging the long- and short-range structures of silica particulate layers at water-air interfaces and on mica supports by using Brewster-angle and atomic force microscopies.