Sol-gel alkoxides an very often sensitive to the surrounding air humidity, especially when the chemical evolution of the sol is operating at time scales comparable to the water-molecule diffusion from the surrounding air inside the medium and their interaction with the alkoxide molecules. The present study reports the in situ observation and interpretation of hydrolysis/condensation reactions occurring within the surface layers of pure titanium(IV) butoxide exposed to air, which illustrates the interest of the methodology for studies of near-surface chemistry in sol gel evolutions and thin films.