I have black matte finish shower tiles with black grout. I have scrubbed the tiles and grout with a 1:2:1 peroxide:baking soda:dish soap ratio.

Tile and grout cleaned up and all soap scum removed but white residue is left behind on some of the grout areas. All tiles and grout were scrubbed and rinsed twice before drying.

This shower sat unused for multiple years and had been temporarily caulked in places prior to this cleaning. I have noticed there is water under the tiles that seeps up when stepped on as well.

Any ideas what this could be?

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  • 1
    If water is coming up between the tiles then cleaning the tiles is not the immediate concern. Stopping water from getting under tiles is of paramount importance. Why clean them if you may have to remove them?
    – Alaska Man
    Dec 19 '20 at 21:35
  • At the moment, we are just looking to get the grout between the tiles clean and find the spots with pitting or missing grout so it can all be re-grouted. Not prepared to remove the tiles at the moment but certainly looking to make sure they are dry and then regrout the spaces to prevent any further water from getting under them Dec 19 '20 at 21:39
  • unsure if this is water staining, or calcium buildup maybe? and if so, not sure how to clean it on colored grout Dec 19 '20 at 22:06
  • 1
    "certainly looking to make sure they are dry" How do you propose to do that? How will you know when it is dry? There are grout scraping tools that will "sand" off the top layer.
    – Alaska Man
    Dec 19 '20 at 22:13
  • 1
    Efflorescence. Don't think of it as a stain; it's an ongoing process. That grout has failed. The tiles are squishy. That's a gut job. You are "at that point" you just don't want to be.
    – Mazura
    Dec 20 '20 at 2:30

To clean grout, I would start with a mixture of white vinegar and baking soda, in a 2:1 or weaker ratio. Apply the mixture to the grout lines, let it sit, gently scrub with a soft bristle brush (old tooth brushes, for example), then rinse with clean water. Repeat if necessary.

If that doesn't work, you then might want to try some of the more powerful commercial products.

  • I'm concerned about using vinegar on porous masonry as I had read it would be too harsh. I was recommended to use hydrogen peroxide instead. This is a slate type tile rather than the standard glossy porcelain bathroom tile. This might be hard water staining/calcium buildup...would vinegar be effective on that? Dec 19 '20 at 22:23
  • I've only used the vinegar/baking soda mixture on glazed tiles. So I can't speak as to whether that would stain/harm a slate tile or not. Soaking something like a shower head in a vinegar/water solution is one of the ways recommended to remove hard water deposits.
    – SteveSh
    Dec 19 '20 at 23:02

The white substance is minerals that were deposited when water evaporated. This can easily be removed in several ways. The fastest and easiest is to purchase a de-scaler (Lime-a-way is one brand name). Simply scrub it on with a brush and watch the scale fizz away!

If you'd rather use a less harsh product any citric acid-type liquid will work (lemon juice in a concentrate). Or white vinegar, but it will take much longer.

Which ever product you use wipe down the cleaned area with a wet sponge or rag to remove any residual descaling/citric acid which could weaken the grout joints.

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