Removing unsightly mold and mildew stains from your white tile grout can sometimes seem impossible. Don’t give up and re-grout the entire kitchen or bathroom just yet, though. If you follow these steps, you can get your tile grout shining white again and keep it that way.
The first step is to get rid of any mold or dirt. Using a new stiff-bristled nylon scrub brush and a bathroom cleaning spray, thoroughly scrub the grout and the tiles. Use plenty of cleaner and rinse well with water.
Next, soak paper towels with white vinegar and place them over any dull patches that are left on the tiles. Press the towels closely into the lines of the grouting. Leave them there for a few hours while the mildly acid vinegar fizzes away any hard water deposits. Come back every hour or so to moisten the towels with more vinegar. Remove the towels and rinse the tiles and grouting well to get rid of any remaining traces of vinegar or other cleaning products.
It’s a bad idea to apply chlorine bleach to mold, as this can produce unpleasant fumes. Since you’ve removed the actual mold and mildew, it’s now reasonably safe to use chlorine bleach on the grout. This kind of bleach needs careful handling. It can irritate and burn skin and eyes, removes color from dyed fabrics and can provoke allergies. An alternative to chlorine bleach is oxygen bleach (strong hydrogen peroxide). Needless to say, you should not bleach colored grout.
Soak paper towels in your chosen bleach and stick them to the tiles as before. Leave in place for a few hours, moistening periodically with bleach and ensuring that they maintain good contact with the grout. It might take some hours, even a day or two in the case of heavy staining; but don’t give up. Eventually, the stains will be gone.
To keep grout white, apply a good quality silicone sealant to clean, dry grout. Daily rinsing with clean water will also help prevent the mold from coming back.