Every tile covering with a high water absorption capacity will absorb moisture if the installed tiling is exposed to water. As a result. the tile body acquires a darker appearance. This discoloration is promoted by water-permeable joints. by layers forming moisture barriers in the substrate (water becomes trapped between the moisture barrier and the glaze). by self-sealing thin-bed cements. and by high humidity in bathrooms with inadequate ventilation or air circulation. In principle. the ceramic body will always dry out again. The greater the extent to which a room is used. the more important it is to ensure thorough and regular airing.