Repair a crack in the grout yourself By KEITH A. PAUL Grout is construction material mainly composed of water, cement and sand, and it needs proper cleaning and sealants. A grout sealer typically is silicone- or water-based and used to protect the grout against water, dirt, mildew and other contaminants. Over time, the sealer will lose its effectiveness and should be reapplied every two to three years depending on the use of the floor.
Believe it or not you can paint over grout. If you don't want to go through the hassle of removing and placing grout, or ripping off and installing new tiles, a bit of acrylic craft paint can go a long way towards giving a bathroom a new look. In this case, black paint was applied over the grout to provide a contrast with plain white tiles. After painting, apply a grout sealer to seal the paint.