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Someone I know had tile laid in their kitchen and was supposed to seal the grout after the work was done. This never happened and now they have dirty grout. What's the best way to make the grout look new?

Is re-grouting an option? By that I mean just putting a new thin layer of grout over top the old stuff to hide it.

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up vote 5 down vote accepted

Don't re-grout, clean it! Talking with a Home depot guy last year about this and he was amazed I still had to use a brush. He shows me this stuff called oxygen bleach from Ajax. This was literally the easiest method I have ever used. Make a solution with just enough hot water to dissolve it, apply and let it sit for 15-20 min and mop off. That easy. I will never use a tile brush again. Once you get it sparkling white, you can upkeep it my adding a small amount every time you mop and you will have pearly white floors forever.

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can this be used on marble tiles ? – NimChimpsky Apr 10 '12 at 15:16
I would hazard a guess and say yes. Bleach is basic, and marble is a calcite so it shouldn't be affected. Spot test to be sure though! – Malfist Feb 26 '13 at 20:21

Regrouting is an option if all attempts at cleaning have failed, but I'd scrape some of the old grout away first otherwise the new grout will be too thin and even when sealed will be more likely to wear badly.

You don't have to get all of the old grout out - just make sure you have 2-3mm depth to work with.

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Yes, oxygen bleach is good. Another brand I have used is Stain Solver.

I don't think you can regrout. Grout is not designed to be a skim coat on top of other grout.

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Our house has 2000 sq ft of grout (with tile in between). I have tried oxygen bleach and almost everything else I heard about. Finally found Acid Magic. Dilute it with water, pour it on, wait about one or two minutes, rinse and done. I use a floor mate to rinse and dry the floor. I am thrilled with the results.

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A concrete acid wash , well diluted, about 20 parts water to one of acid, will clean any grout on the floor. But be certain to add the acid to the water, not the other way around, also its an idiot that doesn't use good safety glasses, gloves and caution. Wash down thoroughly after wards with plenty of water.

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