For the 60x60cm black tile, we did black grout in the bathroom. At first, the whole grout was nice and black. However, since some time, some of the grout has turned white.
If you get them wet in the shower, for example, the grout immediately turns black again. When they dry, they become white again.
What can we do about it?
Colored grout never stays as good as new.
Same thing with me. It always starts with limescale, although typical remedies like vinegar and citric acid don't help with it.
Could it be because of the harsh bathroom cleaners?