Aluminum (Al) coatings on microspheres offer advantages in developing retroreflective surfaces for high visibility materials and applications. The hemispherical (half-shell) aluminum coating creates the mechanism for
retroreflectivity as the light passes through the clear half of the
glass bead and “bounces” off the reflective aluminum-coated back surface, directing
the light back to the source or the viewer. Additional surface coatings (silane or fluorochemical) ensure that the spheres remain on the surface of the formulation, thereby enhancing the effect of retroreflectivity.