The enamel layer of a toilet bowl becomes more porous as it ages. As a result, the toilet bowl more easily retains deposits such as limescale or urine scale and then mixes with other dirt. These often very persistent deposits occur not only in the visible part of the toilet bowl, such as the neck, but also invisibly under the rim. In particular, deposits under the rim of the toilet bowl ensure that the toilet is never really hygienically clean and that a musty smell lingers in the toilet room. Moreover, a deposit under the rim negatively affects the proper flushing action of the toilet.