The manufacture of machined aluminum parts creates machining marks or etching on the metal (see the picture above). Abrasive blasting the surface with Glass Bead will produce a uniform surface finish. The Glass Bead is typically blasted at 60-80 psi at a perpendicular (90 degree) angle to the surface. This produces a peened effect for a unique result. Grit type blasting media such as Aluminum Oxide will also remove machine marks but will leave the aluminum or other types of metals with an etched, rough surface finish. The picture shows the same part after blasting with Fine (#13) Glass Bead to produce a very smooth, matte result.