Glass fibers with different surface properties (differently sized and unsized) have been investigated by means of inverse gas chromatography (IGC) at infinite dilution as well as by UV/Vis spectroscopy of solvatochromic probe dye molecules. Surface acid-base parameters obtained from the specific energies of adsorption of polar probes using IGC were compared with empirical polarity parameters obtained from shifts in the UV/Vis absorption maxima of adsorbed solvatochromic probe dyes. Both methods give useful information on surface characteristics. Solvatochromism seems to be suitable for a quick sizing characterization and, therefore, this method may become a significant surface analytical tool in the field of adhesion compared with the established IGC methodology.