Grout is a mixture of water, cement, and sand used to fill the spaces between tile in bathrooms, kitchens, and on floors. Most people don’t think about grout, or try not to, but over time this porous substance becomes a magnet for mold and mildew. This is especially true in the bathroom and kitchen where constant heat and moisture makes a fertile breeding ground for nasty, staining fungi. Those who are allergic to mold and mildew can have real health concerns when grout sprouts. But even those without allergies need to treat grout when it becomes stained—because the mold will keep growing. It might get behind your walls and spread throughout the rest of your home, and then you can have a real problem.
Fortunately, even the dirtiest grout can be cleaned. The key is to clean grout regularly. Apply cream cleanser to a stiff bristle toothbrush or a tile brush and scrub away between those tiles. Don’t forget the caulking around the edges of the tub, sink, and toilet bowl. When you’re finished, rinse with fresh warm water and dry the grout with a clean towel.
Left untreated, some grout just won’t come clean. In such cases, bleach may be needed. Bleach is a strong chemical and needs to be handled with care. Put on some rubber gloves and open a window or turn on the ceiling fan. (Do not mix bleach with ammonia cleaning products; the mixture emits toxic fumes which can be life-threatening.) Mix 3 parts water to 1 part bleach and apply to the grout with a damp sponge. Wait 10 minutes and soak the grout again. Wait another 10 minutes and rinse with water.
Out With the Grout
If your grout remains black, you might have to resort to a little construction 101 and re-grout the tile. For small areas use a grout removal tool, or grout rake, with a carbide blade. Slowly pull the tool along the grout, making sure the bit is the right size for the space between the tiles. If you’re seeing colored dust, you’re hitting the tiles. For large areas of more than 30 square feet, use a rotary grout tool. You don’t need to remove all of the grout, just stained or crumbling areas.
Fill in the Spaces
Once the joints are cleaned out, take a stiff bristle brush and scrub them clean of dust, grit, and loose debris. Mix up a bucket of fresh grout or use pre-mixed grout. Apply it with a grout float, smearing it across the surface of the tiles and deep in the joints. Wait 20 minutes and use a large grout sponge to wipe the tile surfaces clean of all residue. Do not use the area for 48 hours while the grout cures. When the grout is fully cured, apply a silicon-based sealer to increase water and stain resistance.