Aspects relate to a drum (10) for rotatably mounting in an apparatus for use in the treatment of substrates with a solid particulate material; a method of treating a substrate comprising agitating the substrate in a drum (10); and a kit for converting an apparatus to comprise the drum (10). The drum has an inner surface (15) and an end wall (2) and access means (70) for introducing said substrates into said drum, wherein said drum (10) comprises: •(a) storage means (4) for storage of said solid particulate material, wherein at least part of said storage means is or comprises at least one cavity located in said end wall (2) of said drum (10); and•(c) a dispensing aperture (12) for dispensing solid particulate material from said storage means (4) into the interior of said drum (10), wherein said dispensing aperture (12) is comprised in said end wall (2) of said drum, characterised in that said drum (10) comprises a valve (6) that is actuatable between a closed position and an open position, wherein when said valve (6) is in said closed position said solid particulate material is prevented from passing through said dispensing aperture (12) and when said valve (6) is in said open position said solid particulate material is permitted to pass through said dispensing aperture (12).