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Removing Grout From Slate Tiles

How do I remove a grout nightmare from my very pourous Indian, multi-coloured, un-sealed, slate tile? The genius who installed it, left the gour over-night and now my floor is wrecked!!!!! Help Please!

Adrienne

Hello Adrienne,

You need to acid wash the floor. There are several grout haze cleaning products sold at your local HomeDepot, Lowes or Ceramic Tile store but they all rely on three active chemicals. Phosphoric Acid, Sulfamic Acid or Amonia-bifloride. I mention this because you should try a “grout haze remover” first. However, it might not be strong enough to do your messy job. In which case, you need to go with a potent solution. For a very potent product, search for a “concrete acid etching product”. The product used when preparing concrete for painting or staining. This is strong phosphoric acid and may even have some ammonia bi-floride in it. Test it in a small area for desired results.

Note, these strong products love to eat calcium carbonate base materials such as marble and limestone. Slate is a different composition so you will not have the same detrimental etching results as marble. Still, discoloration may occur so if you go with the heavy duty solution, test it first. ear gloves and protect your eyes as well.

Best wishes,
Tom Cordova

This entry was posted on Monday, September 11th, 2006 at 7:25 pm and is filed under Questions About Slate, Regarding Other Kinds Of Stone.... You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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9 Questions Recently Posted:


  1. December 20th, 2007 at 2:39 pm

    We just installed new granite countertops (Venetian Gold) and natural stone backsplash with cornsilk-color grout. The granite wasn’t sealed yet, and the installer wiped the counters repeatedly as he was cleaning up the grout. Now the edges of the counters and some areas on top have the tiny cracks filled with grout, which I can’t get out. The grout looks white in the granite, and it looks like little tiny spider veins, all along the edge.

    I’ve tried scrubbing with a brush, wiping, but nothing helps. The white cracks disappear when the granite is wet, but then they are right back. How can I get the grout out of the tiny crevices without destroying the shine of the granite?

    Thank you.


  2. April 12th, 2008 at 10:02 am

    i left sanded grout overnight on autumn tumbled slate 2×2x12 tile and it is 1/8 to 1/4″ thick on tile and the unsanded grout has left a thick film on the rest. i started using a hard wood stick to remove the thinner parts and scrubbing pads for thick film; is there an easier solution to my mess? thank you for your help. geoff


  3. May 14th, 2009 at 1:08 pm

    I installed a natural stone tile shower and we grouted over all of the stone as we would have with any other tile. But, since natural stone is more porous than some others, the stone was discolored a little. I am wondering if there is a way to restore it without damaging or having to replace it. Thank you for your help if you are able to.


  4. March 1st, 2010 at 12:40 pm

    I used slate tile as my back splash in the kitchen. We didnt know to seal it first, and the sanded grout (dark blue-grey) has seemed to completely ruined the slate. I have wiped it over 7 times and still the look is not right. I am upset. Should I keep scrubbing and hopefully more will come off? The slate seemed to have taken on more of the grout then expected and now my grey tiles are closer to the grout colour. I dont want to use chemicals, as they might damage/stain the slate further.


  5. June 15th, 2010 at 6:49 pm

    We just installed new granite countertops and natural stone backsplash with cream grout. The granite wasn’t sealed yet, and the installer wiped the counters repeatedly as he was cleaning up the grout. Now the counters and some areas on top have the tiny cracks filled with grout, which I can’t get out. The grout looks white in the granite, and it looks like little tiny spider veins, all along the edge.
    The white cracks disappear when the granite is wet, but then they are right back. How can I get the grout out of the tiny crevices without destroying the shine of the granite?


  6. May 1st, 2011 at 10:41 pm

    I have the same grout on my slate patio floors. I am using Dupont’s Grout Haze Remover and periodic usage is getting it off bit by bit.

    My question is in two parts – how much time do I have to wait from the last time I use the Grout Haze Remover to sealing the tiles? The slate is multi colored quartz and I am not sure of its origin. This is for my outdoor patio

    My second question – I am looking for a sealer that has a glossy finish (wet look and glossy). I am thinking of using Behr 985 wet look sealer. Is this a good one and will this make my slate floor overly slippery when it is wet – currently my odd shaped tiles are very rough and bumpy to the touch.

    Thank you in advance


  7. June 8th, 2011 at 9:24 pm

    how can i remove wax or sealant of grinite floor suggest well working chemical


  8. October 16th, 2011 at 5:17 am

    I have unsealed Indian multi colored slate tile. I just installed it being careful to wipe off the grout with a sponge. Would it be possible to wipe down the haze the next day, or would I need to go to extreme measures for grout hazing?


  9. March 4th, 2012 at 2:53 pm

    how do u get grout off porcelaine granito tiles? i sure hope you can help me. thx

    —–
    Use sulfamic acid from home depot.

    Regards,
    Tom