Abstract: Directing a laser beam at a surface to be treated, such as a metallic surface which is likely to reflect much of the energy, results in a high proportion of absorbed energy if the laser beam has an oblique incidence, particularly if the laser beam is polarized in a direction parallel to the plane of incidence (defined as the plane which contains the axis of the laser beam and the perpendicular to the surface at the center of the spot of incidence). In the case of iron and steel surfaces the absorbtion is markedly increased at angles of incidence greater than 45.degree. and just short of glancing incidence, with a maximum near 80.degree..