If the white grout in your bathroom or kitchen tile is looking a bit worse for wear, your first instinct may be to have the tile re-grouted. However, this can be difficult and time-consuming. Unless there are missing pieces of grout, it's really not necessary. You can get your white grout looking bright and fresh again with a little elbow grease and these steps:
Step 1: Bleaching the grout.
Bleach alone won't usually restore white grout to its original, pristine appearance, but it does serve another very important function. It kills any bacteria and mold spores in the grout, so that when you apply the grout whitener (in a later step) you're not just sealing in these organisms and waiting for them to proliferate and make more stains.
To bleach your grout, prepare a mixture of about 1 cup bleach in a bucket of water. Dip a rag in the mixture, and then wipe it over the grout, being generous with the water so that it soaks into the grout a little. If you can see any mold, scrub it away with a toothbrush. Let the bleach water sit for about 5 minutes, and then soak it up with a sponge or cloth. Let the grout dry for at least 24 hours before proceeding.
Step 2: Applying grout whitener.
Grout whitener is essentially a white-tinted sealant you can apply to the grout. It can be purchased at home improvement stores, and it comes with a special applicator that looks like a wheel.
To apply the grout whitener, start at the end of one line of grout, and roll the wheel along the length of that line of grout. It may take you a little trial and error to figure out how hard you have to press down on the applicator to release the right amount of grout whitener. Repeat this process until you have applied whitener to all of the grout lines in the area.
Step 3: Removing excess whitener and smoothing out the final results.
Chances are, your freshly applied grout whitener looks a bit jagged. Wait until it has dried partially (about 2-3 hours), and then wipe over it all with a slightly damp cloth. This should blur the line between the grout whitener and the tile, making for a more natural look. Don't use a cloth that's too wet, or you'll simple wipe away all of the whitener.
Let the grout whitener dry for 2-3 days before attempting to clean the floor. By this time, it should be impervious to water and mild floor cleaners.
For further assistance, contact local professionals, such as those from All American Stone & Tile Care Inc.