Grout must set for 15 to 30 minutes before it is wiped for the first time and another 3 hours before it is wiped a second time, according to BobVila.com. In both stages, the grout should be wiped with a wet sponge to remove excess grout on the tile.
The grout must be allowed to dry for several hours or overnight after the wet wipe. Once the grout is dry, a haze forms on the tile. The haze should be rubbed loose with a dry towel, and then the remaining dust must be swept off. Using a wet towel for the last step often causes the haze to form again.