Stone Mosaic Backsplash before grouting cropped

Grout Color for Stone Backsplash

Randy Evans emailed me a photo of his stone mosaic backsplash and asked for advice in choosing a grout color.

Even though this project isn’t figurative mosaic, and the grout gaps have the width of masonry joints (much larger than the gaps recommended for small glass mosaic tiles), it still makes a good teaching example about how to choose a grout color for your own mosaic for these reasons.

  1. Randy worked through the decision in a thorough way using basic methods BEFORE testing colors in hidden places in the backsplash.
  2. Randy took some good photos of his experiments, plus one of the installation as a whole that shows the importance of hue in making a backsplash work with the room’s color scheme.

You could use the same approach for picking out the color mortar you wanted to use for a stone or masonry surface.

TIP: You can minimize the color impact of grouting glass mosaic by using smaller grout gaps. It also makes grouting easier. Highly recommended.

CAUTION: A grout gap is needed in architectural mosaics because the grout is needed to seal out water, which can’t be sealed out merely by making the tiles touch each other.

My Default Recommendation

The purpose of grout color in a mosaic made from different colored tiles is to adequately contrast each of those tile colors. Otherwise, the “mosaic effect” can be lost visually in areas of the mosaic where the grout matches the tiles.

My default recommendation for grout color for a mosaic made from small glass tiles is to use a medium gray, meaning a medium between black and white without any particular hue, unless there is a light cyan blue area in the mosaic, such as for a sky or water .

An Important Caveat

If there is an area of light cyan blue in the mosaic, I point out you have to make sure the gray is dark enough to contrast the blue. I also point out that you can also also get enough contrast by using a grout that has a warm hue, something like a dull brown or muted terracotta.

The brightness should still be a medium, especially if you want to avoid the grout standing out too prominently in areas of the mosaic that are darker or lighter than the rest.

Of course the default to a neutral gray of medium brightness is based on the assumption that the grout gap is relatively small and not a significant source of color.

And you wouldn’t want to use a neutral gray on a mosaic of a southwestern landscape at sunset because the “neutral” gray might actually look bluish against all that warm red earth tones and flaming sky.

Hue and Architectural Mosaic

In polychromatic mosaic art, grout color is about adequately contrasting all the tile colors.

For architectural installations, the grout color has to take into account the color scheme of the room, especially if the grout gaps are as large as masonry joints and the tiles are small, which was the case in Randy’s project.

In Randy’s project, the grout is as much a source of color as the tile itself, and its hue will be based on harmony with the room as much as it is based on tile contrast.

The rest of this article are standard methods/tips illustrated with Randy’s photos.

Stone Mosaic Backsplash before grouting
Stone Mosaic Backsplash before grouting

Look from Afar or at Photo

TIP: If you look at a photo of a small-gap mosaic before it is grouted, you can often see what the mosaic would look like with a medium gray grout, meaning a medium between black and white because the shadows in the narrow gaps are about that gray.

If you look at Randy’s ungrouted mosaic above, you can see that the shadows in the gaps between the stones are about a medium gray.

But the grey in this photo are not a neutral gray because the photo was made in a room where the light was tinted by the room’s warm brown color scheme.

That means the usual “medium gray” is in this case more of a medium brown.

Esoterica: In painting, an infinite number of “grays” can be made by mixing a single pair of contrasting hues (say orange and blue) plus white. These grays can look like different types of dark mud when the hues are relatively balanced or like muddy versions of either hue when only a tiny amount of the other hue is mixed in. And then the amount of white can be varied to create an infinite number of tints.

IMO, I think mosaics look best when the grout color is more like a mud than a muddy version of a color.

Stone Mosaic Backsplash Grout Color Swatch
Stone Mosaic Backsplash Grout Color Swatch held against ungrouted mosaic

Paper Color Swatch

Get a paper swatch of grout colors from a building material store and hold it up against your ungrouted mosaic.

Make Some Grout Biscuits

If you aren’t convinced by a paper color swatch held against your mosaic, you can always make some slugs of grout or grout biscuits. Everyone loves the concrete biscuits that grandma used to make using grout.

Stone Mosaic Backsplash grout biscuit/slugs test blanks
Stone Mosaic Backsplash grout biscuit/slugs test blanks.

Note that a color looks different based on the colors around them, and so the grout biscuits above shouldn’t be evaluated side by side or laying on a brown kraft paper surface. Instead, they should be held one at a time up against the ungrouted mosaic.

TIP. More useful that grout biscuits are grouted test swatches, Get a scrap piece of mosaic mounted to a scrap piece of plywood and grout it with a couple of grout colors.

Test In Hidden Spot

For an architectural coverings, you can grout in a spot that would be hidden or covered, such as behind a stove as Randy did below. You can also make a small test plaque on a scrap piece of plywood.

Stone Mosaic Backsplash color study behind oven
Stone Mosaic Backsplash color study behind oven where it will be hidden from view. Notice how bad the white grouts section looks due to the lack of contrast with the light colored stones. Notice how severe the dark gray looks due to the extreme contrast and the lack of harmony of hue.
Stone Mosaic Backsplash color study
Stone Mosaic Backsplash color study. Notice how the light grout doesn’t look as good as the brown because the light grout is about the same color as the stones it fails to contrast.

Grouted Backsplash

Stone Mosaic Backsplash grouted
Stone Mosaic Backsplash grouted.




14 responses to “Grout Color for Stone Backsplash”

  1. Sandra Forrest Avatar

    This was so helpful, thank you. I realized I was not investigating the variety of grout colors available, sticking to dark gray mostly. Great idea to show the possibilities side by side. Love it.

  2. isabel Avatar

    nice example and solutions.

  3. Karen Avatar

    It was really helpful to see the steps used to determine the grout color. I have started making small test boards with all the tessera I’m considering using in a project, and a few grout options. This has allowed me to eliminate colors of tiles completely, before I even begin, and often I’m surprised by which ones need to go. (Sometimes I’m so excited to start, I just want to get going smashing plates and arranging colors on my work surface….) I made a couple nice pieces early on in which one tile color just got lost in the grout and I now appreciate the importance and wisdom of slowing down a bit and considering the grout color in the planning stages.

  4. Teresa Murphy Avatar
    Teresa Murphy

    Thanks, that was a very informative post. Really nice to see the different grout options in situ before the final selection was made. Thanks for the effort. Appreciated!

  5. Kathy DiGrazia Avatar
    Kathy DiGrazia

    What color was ultimately recommended and/or used?

    1. Joe Moorman Avatar
      Joe Moorman

      The color on the swatch named “Linen.”

  6. Ethel Jaske Avatar
    Ethel Jaske

    Awesome info. I would not have thought of testing the grout color in hidden areas. I have just picked a color that looks good with only a quick glance. When I tile our bathroom I am going to follow the advice given.

  7. Kane Carol Avatar
    Kane Carol

    Beautiful installation (made me want to tackle a big box of rocks I actually shipped home from an island in Puget Sound!). And Joe thanks for the inside scoop on deciding on shades of grout color . . . I am working on two small wall ;pieces (needed to use up some stock before I could justify buying more :)) and this helped me immensely.

  8. Sharon Tepe Avatar
    Sharon Tepe

    Thanks for the helpful info. Whenever I have left over grout, I make a flat slab of it, like a biscuit. Then when I am trying to figure out what color to use, I can lay my tesserae right on the biscuit. Of course, as you suggested, a test sample with your tesserae on it works great, too.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Sharon,
      That is a great suggestion. Thanks for contributing something that will help people.

  9. Karen Wall Avatar
    Karen Wall

    I don’t see any grout for sale on your website. Am I missing it?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Karen,
      We are out of stock due to Covid19. Fortunately you can buy grout cheaply from a local building material store.

  10. Susan Klug Avatar

    I’ve gotten lost in the types of grout at the hardware store. Is there a type not to use? Or a specific type to look for? Current projects are made with small to medium glass tesserae. I have also used acrylic paints to tint white grout, and have liked the result.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Susan,
      Any traditional portland-cement grout with sand will work. Those are the grouts that come as a dry powder. We don’t use the urethane and epoxy grouts because of their cost, fumes, and difficulty of clean up.

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