A few months ago we installed slate tiles around our bathtub/shower and we sealed them with 511 Seal & Enhance (by Miracle Sealants) .

Since then we started to notice notice some areas of the slate greyer than others (attached pictures). Should we apply more sealer over the whole tile again ? or we should clean the whole tile and re-apply sealer?

We are worried that we may mess up the tiles more than what they currently are.

enter image description here

  • It's just mildew. Clean it.... Oh greyer... Probably soap buildup or water scale. Clean it.
    – nportelli
    Commented Oct 14, 2015 at 16:03
  • tried cleaning it, that is the color that remains after cleaning, also on the picture there is an area with more washout color and other tiles have some more grey marks, that are the ones I am more worried about.
    – macutan
    Commented Oct 14, 2015 at 16:58
  • Still think it's soap or water scale. Did you use a scrubbie? If it is only a month old it could be the grout still leaching too.
    – nportelli
    Commented Oct 14, 2015 at 17:29
  • I'm going to try lime-away on the grey/whiteish tiles to the right. but I do not what to do about the small grey spots (more visible on the third tile to the left on the bottom row)
    – macutan
    Commented Oct 14, 2015 at 20:54
  • Tried Lime-away several times and the white-ish does not seem to go away after the tile dries. I have read online conflicting statements about whether I could use use acidic cleaner or not on slate. Any thoughts? I bought Heavy Duty Acidic Cleaner (link below) (by Miracle Sealants) and I am wondering if this would strip the existing layer of old sealant (and hopefully the whiteness on the slate) and all I have to do after is re-seal it. miraclesealants.com/…
    – macutan
    Commented Oct 15, 2015 at 12:52


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