  We report on the implementation of evaporative cooling of a magnetically
guided beam by adsorption on a ceramic surface. We use a transverse magnetic
field to shift locally the beam towards the surface, where atoms are
selectively evaporated. With a 5~mm long ceramic piece, we gain a factor
$1.5\pm0.2$ on the phase space density. Our results are consistent with a 100%
efficiency of this evaporation process. The flexible implementation that we
have demonstrated, combined with the very local action of the evaporation zone,
makes this method particularly suited for the evaporative cooling of a beam.
