to cause slight bending at the end of the bristles and in this respect it is noted that contact between the brush 60 and chill 12 is exaggerated in fig1 for illustration purposes only when a casting wheel 12 is employed which has a grooved chill surface 14 of the type illustrated in fig5 the groove spacing measured axially along the surface of the cylindrical chill may be such as to provide from about ten to about forty grooves per centimeter and the grooves may have a depth of from about 0 025 to about 0 60 millimeters when the nylon silicon carbide brush described above is employed with such a grooved chill surface contact between the ends of the brush bristles and the chill is maintained so as to produce a polished oxide surface on the outer or land portion of the grooves but the bristles do not penetrate into the root of the respective grooves with sufficient pressure to remove all the loose oxide particles from this area in use such a chill surface will have the visual appearance of alternate light and dark lines with the light lines being smooth polished oxide areas on the lands and the darker.