The secret to great looking tiles is great looking grout. Grouts are porous and, as a result, they easily absorb grease, dirt and lime scale. Spillages such as wine, lemonades or any greasy substances could cause marks and patches in the joints in the floor. Grout between wall-tiles, particularly in damp areas like bathrooms, could and will become dirty and unattractive as a result of Mould, Mildew and Limescale.
Mould is one of the most unsightly problems, it usually starts off in the wettest area of the room, like the bottom of the shower or bath, and if left unchecked it could spread to cover a large area of the wall.
In bath or shower areas, continued use of acid formulated shampoos and soaps will cause discolouration of grout joints, causing yellow orange and pink stains to appear on the grout over time, so you should protect your grout using a sealer which forms an invisible barrier between the grout and the surface, protecting your investment for years to come.
In general, porous flooring such as Terracotta should be sealed every two to three years to lock in the beauty of the tile and protect it from wear. Mexican terracotta in particular is very porous and difficult to clean. Mexican Terracotta does not get baked in a kiln, instead they are left to bake outside in the sun and if it is a cloudy day the temperature can fluctuate leading to an increase in the porosity of the tile.