Grouting White Marble with Black (Charcoal) Grout

QUESTION:

I just installed a 12x12 marble (polished) checkerboard (white and black) tile in my laundry room. The wife wants black grout (charcoal). Will this penetrate into the white marble? I used white thinset and plan on using unsanded black grout. I obviously do not want to do this if it will bleed into the white. Any help would be greatly appreciated.


ANSWER:

Contrary to what you often read/hear about marble... it is not very porous and does not stain easy... common misconception that it does.

However, the marble tile edges will be more porous than a polished face and the black grout could bleed and cause some discoloration to the white tiles since it will be in contact with the marble and wet for quite a while before curing.

This can occur when using a darker colored thinset too.

But using a lighter colored grout may not be the answer since it could also bleed into the black tiles making the edges look foggy.

And a light colored grout will show dirt way more than the dark grout.

The most effective way to combat this potential problem is to seal the marble tile edges before applying the grout.

If the tiles are polished, then the face most likely will not need (nor will it take or be able to absorb) a sealer.

Polished marble is nearly non-absorbent and rarely needs sealing. All you need to do though is water test the marble.

The unpolished edges though will be more absorbent and should take a sealer. We suggest using these recommended marble & granite sealers.

You must take care not to let any sealer residue remain or dry on the face (if polished) or it will leave a streaky haze that will require stripping.

You could also simply perform a test with some left over tiles. Set them on a level surface (piece of plywood, etc.) and apply the grout. Let sit for a couple days and see if any absorption/discoloration occurs.

Comments for Grouting White Marble with Black (Charcoal) Grout

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Test Marble Thoroughly with Dark Grout
by: Jules

We just had white marble flooring installed with black granite tile in a checkerboard pattern.

The contractors did an amazing job of tile placement and we ended up ordering more marble tiles than planned because some of the ones we got were chipped or had a spot that looked like dirt, etc.

We were offered a choice of grout color, and selected black (which I still do not regret) and the contractors grouted all 1,000 square feet (give or take) within a day.

They had sealed the white polished marble tile before grouting. We were super psyched, except... it looks awful. So bad.

The black grout itself looks amazing, but the marble looks terrible, like someone had done a rubbing on it with black crayon.

Our contractors have tried to get it out with limited success, and are blaming us for choosing the grout color, but if you go with white marble and black grout (which I still think is an amazing combo, if you can keep the marble clean) make sure to get extra tiles and test test test.

Rub the grout all over a spare tile or two. Also, if your marble tiles have rough edges or chips, they will become super noticeable.

==== Countertop Specialty comment:

Well, when using a dark grout with white or light tile you can get a "picture frame" effect when the dark grout absorbs into the white tile.

However, this is usually (and successfully) prevented by sealing the tiles prior to grouting, which you said they did do.

Either they did not seal the tile or tile edges well, or didn't actually seal the tiles, or mixed an especially wet grout that took a long time to set and dry.

Sealing will help prevent staining but won't absolutely stop it. Sealers work by increasing time to absorption but won't prevent it completely.

If a spill or a stone surface is exposed for a long time to a liquid, it could still absorb and stain even when sealed.

The other possible issue is that you have "grout haze". I think you'd probably recognize the difference as the grout haze would look like smears all over the tiles (both the white marble and black granite).

If you think it is just grout haze, then use this Hard Water (and grout haze) Remover.

It works great to remove grout haze, hard water deposits around the sink and in the shower, and soap scum in the shower.

Of course, it is safe for use on marble and all natural stone where most grout haze cleaners are not safe for marble and will etch it.

Have a related question
by: Anonymous

Sorry for hi-jacking this thread but it’s related, so hopeful this is okay.

We just put in a basket weave (very small) marble tile in our powder room. The grout we used was too light, and it does not show off the basketweave pattern.

I’d like to darken the grout. What is the best way to do that without ruining our marble tile floor? This is a new build. Thank you.

===== Countertop Specialty comment:

Well, you could dye the grout lines, but that would be a super-tedious job. And you don't want to get it on the marble.

Possibly applying a Color-Enhancing Sealer to darken stone would help, but it will darken both the marble and the grout.

The idea is that possibly it would darken the grout more, but that is a total gamble. No guarantee that it would.

Just accepting it is probably the best option.

Yes It Stains
by: Anonymous

We installed a basketweave white w/ black dot polished marble floor.

We tested black epoxy grout which isn't supposed to bleed at all but it did. Turned our white marble to grey after just an hour or two.

We settled on a grey epoxy grout which didn't have such a drastic effect on the tile but still did bleed. The bleeding wasn't uniform so it has some dingy spots.

Don't have a solution for you, just a word of caution. Dark grout (both cement and epoxy) will bleed into white marble.

Thank you
by: Anonymous

great information. Would Mapei Grout Refresh Grout Colorant work to change the grout to black?

==== Comment: Yes, I believe that would work, but you should contact Mapei to get complete product use information.

Grouting white marble mosaic bathroom floor
by: Anonymous

I am restoring a 1920's white marble mosaic bathroom floor; I am considering re-grouting in black but want to make certain of any necessary precautions/steps to avoid possible staining.
Thanks

===== Admin Comment:

You'll want to water test the marble to see how absorbent it is first.

Test the edges as well. If absorbent, then yes you'll want to seal the tiles and edges prior to grouting.

If possible (with some unused tiles) run a test by setting a few of the marble mosaic tiles on wood or some other temporary surface and grout this "sample" section. Note if you get any bleeding of the color.

If not and/or if testing shows low absorbency, then you may be fine not sealing the mosaic tiles.

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