The majority of work available in the literature examines the effect of epoxy silane, gamma-aminopropyltrimethoxy silane, and methacrylate silane on E-glass surfaces. As alternatives to the most commonly used silanes, we investigated two novel silanes: gamma-ureidopropyltriethoxy silane and Nbeta(aminoethyl) gamma-aminotrimethoxy silane and additionally an amino-functional polysiloxane. The ureido silane-treated E-glass fibers demonstrated a zeta potential similar to that of the untreated E-glass fibers, which was independent of deposition solution pH over the pH range investigated. A moderately hydrophobic E-glass surface, which was silane concentration dependent, was noted as being due to condensed Si-O-Si bonds at the surface. The diamino silane demonstrated an extremely basic surface at the higher silane concentrations investigated. These outer surface layers were modified by changing the pH and the concentration of the deposition solution. The polysiloxane produced an increase in the hydrophobicity of the E-glass fiber, especially when deposited from extremely basic solutions. At the higher solution concentrations investigated, the silanes and the siloxane was initially deposited in patches and an outer surface or "skin" was formed over these patches, giving the appearance of fully coated fibers. Copyright 2001 Academic Press.