Sodium bicarbonate
Tile grout can be hard to clean. In many cases it is not only Earth, but also the appearance of mold that has become stuck in the seams between the porous tiles. The best way to keep it from being stained beyond repair is to seal the grout with a sealant. This way the contaminants are not able to get down on the seams and the mold cannot grow.
However, if the stains are already there, they will have to be eliminated. One way to get rid of the stains is the use of baking soda. Wet the grout and spray the area with baking soda. Let stand for several minutes and rub with a brush. Repeat the application if necessary. Clean the area with a damp cloth.
Bleach
In more difficult circumstances, spray in a mixture of a part of water and a part of chlorine. Keep the area well ventilated, or if you are in a bath leave the air extractor on. Let the mixture set for about ten minutes and then rub. Do not rub together by spraying the mixture once a day for one or two weeks without scratching. The appearance of mold will slowly disappear on its own. After grout is clean, use this solution once a week to keep the area free of stains and dirt.
Vinegar
A last method for cleaning tile grout is the use of white vinegar. Vinegar is a good way to kill mildew and fungi due to the acid content of vinegar. Pour the liquid over the grout with a spray bottle or pour on a washcloth. Once in place, scrub the grout with a brush or rag. After cleaning, wash with plain hot water. Then dry with a dry towel.