Suntest PMMA plates of 5 cm 5 cm
have been purchased from SCHO¨ NBERG GmbH (Munich,
Germany). The plates have been cut from a large sheet of UVstabilised
Plexiglas1 and roughened on one side by an industrial
sandblasting procedure (glasspearls, 90–150 mm, 30 cm, 6 bar).