Mosaic Coffee Table Pre-Grouting

Changing Grout Color With Paint

The following method is only recommended for dry indoor mosaics. Artist Megan Adams recently used it to save a mosaic that had been compromised by white grout, which makes tile colors look less intense and the mosaic as a whole “bleached out” in appearance.

We put white grout in bathrooms because it is used as an indicator of cleanliness. It’s use in mosaic art is limited to making your project look like a summer camp project. Avoid it. Consider black or dark gray grout instead to make your colors look intense.

Also keep in mind that traditional sanded grout is lighter in color when it hardens, and so sometimes a light gray or light brown grout can turn out looking like an off-white and cause the same problem as if you had used white grout.

To minimize the impact of grout color on your mosaic, use a small grout gap, (For wet and outdoor mosaics, you must use a gap wide enough for grout to fit into so that water cannot seep into hairline cracks between tiles.)

I originally wrote these instructions as part of an article about using “test swatches” of tile glued to pieces of plywood to see what different grout colors would look like with all the tile colors of a particular mosaic.

Here is Megan’s mosaic after grouting with white grout:

Mosaic Coffee Table by artist Megan Adams with white grout bleaching out the colors.
Mosaic Coffee Table by artist Megan Adams with white grout “bleaching out” the intensity of the tile colors.

Notice how the grouted mosaic above is less intense in color than the ungrouted mosaic .

The following is the mosaic after darkening the grout with a wipe-on/wipe-off “stain” of acrylic paint. Note that the photo was taken in saturated sunlight, and so that it looks more “bleached out” for that reason compared to how it would look in the more normal lighting used for the previous photo:

Mosaic Coffee Table by artist Megan Adams with stained grout.
Mosaic Coffee Table by artist Megan Adams with stained grout.

Method for Changing Grout Color

If you want to change the color of a grout line in a finished indoor art mosaic, you can do that with artist’s acrylic paint applied via wipe-on-wipe-off using a rag. You get it applied and wiped off quickly before the paint can dry on the glass. The paint sticks in the porous grout so that it doesn’t wipe off.

I recommend diluting the paint with acrylic media to make a water-based “grout stain.” You can also apply undiluted paint for a more opaque covering of the existing color, which might be simpler for most people.

I recommend experimenting on any piece of scrap material to figure out colors and dilutions.

I recommend testing on a grouted tile swatch before applying to the mosaic to see how it actually looks on the grout.

I recommend Yellow Ochre and Burnt Umber. Both are UV resistant mineral pigments and considered non-toxic. They also make great stains.

You can also use Ivory Black and Titanium White to make hue-neutral grays of every shade, but a wide range of colors are available, and you can make more interesting grays too.

I would avoid toxic Cadmium Yellows but Nickel Yellows are considered safe.

I would avoid making my grout paint more intense in color than the tile colors.




15 responses to “Changing Grout Color With Paint”

  1. Mary Avatar

    Please explain what you mean by “acrylic media”. Also, for the colors you refer to such as Ivory Black and Titanium White – what brand of acrylic paint are they?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Mary,
      Acrylic medium is the clear acrylic that artists mix with acrylic paint to make glazes. Ivory black and titanium white are pigment names used by all the major brands of acrylic paint. Thanks!

  2. Bonnie Eisner Avatar
    Bonnie Eisner

    Great advice. I recently used glass paint on a stained glass mosaic portrait as one piece was too white and popped when it was supposed to be a highlight. I mixed a light gray and painted the one piece. Made a huge difference.

  3. Michele Petno Avatar

    Many years ago I needed a specific blue grout color for a commission. I had a WATER BASED wood stain (white base) tinted at Home Depot the exact color I needed. Now I keep a can on hand and pour out what ever I need and tint it with Tints-All. I have only used this method on sanded grout.

    As soon as the grout takes it in be sure to wipe the surface with a damp sponge or cloth to avoid dulling your tiles or glass. As always test first!

  4. Paula Avatar

    I have used this method on a number of mosaics to avoid the “summer camp project” look–a perfect name, by the way. It is much easier than trying to tape off segments of the mosaic to grout different areas with different colors of grout, and much more accurate. As you can see above, it makes a tremendous difference in the final appearance of the mosaics. They look much more like the classic ancient Roman mosaics which did not use grout at all.

  5. Jill Gatwood Avatar

    With a mosaic using grainy vitreous tiles, is there a danger of the paint staining the tiles because of the pores?
    I am not a big risk-taker with grout and, like Joe, I practically always use a dark charcoal grout color. I advise my students to avoid white, but I provide it and sometimes I have been surprised. With solid, bright color tiles, white grout can make the colors pop just like the dark grout does. However white grout tends to fracture a design rather than bring it together like dark grout does. If it is abstract – especially with small grout lines – it can work. Alway best to do a test sample, of course.
    I am most often disappointed by medium gray grout, which seems to dull everything.
    All this being said, when visiting Parque Guell in Barcelona, I noticed Gaudi seemed to ALWAYS use white grout… 🙂

  6. Annette Van der Wethuizen Avatar

    I recently finished a big mosaic project .Sea and sunset picture. I used medium grey grout and is very disappointed.
    The sky which turned from pink to beige at the top is now dull!!!
    Can I paint only the top part with a beige paint.

    1. Joe Moorman Avatar
      Joe Moorman

      Yes. Just tape off the section you don’t want to modify.

  7. Connie Loretta Micheli Avatar
    Connie Loretta Micheli

    Is there any way I can remove sealer from a grouted mosaic table. made the mistake of grouting white and now realize it was a bad mistake as I’ve read above. The table top looks too “pretty pretty” with the white grout as the base is black steel. I’ve read where I can use acrylic paint on the joints but unfortunately I’ve already sealed it, beginners eager mistake.
    Is there any possible solution? can I somehow use a product to remove the sealer? desperately need help as the design is really nice but the grout spoils it. Devastated. 🙁

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Connie,
      I hate to hear that. I know how awful the surprise can be. The sealer is just a superficial pore sealer. Bu scratching it with a stylus (old screwdriver), you could have a grout surface that would adhere to acrylic paint.

  8. Kathy Avatar

    Do you ever do partial grouting? I’ve just completed a seahorse mosaic (tile) with a clear colored glass tiles for the background. I’m thinking of grouting just the seahorse, not the background. Am afraid the grout will ruin the effect of the glass. Will this end up looking unfinished? Should it be all or nothing?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Kathy,
      Email me a picture. If the grout gaps are the same width, it might look odd if part of the mosaic is ungrouted.

  9. Neena Avatar

    I just finished 2 mosaic stepping stones. I grouted and sealed them. The grey is too light, and needs to be darkened. Please tell me there is a way to do this without messing them up.

    1. Joe Moorman Avatar
      Joe Moorman

      Once they are sealed, there isn’t any way to change the color.

    2. Tina Marie Syperda Avatar

      I’m confused about the answer that was given to this question, as I see above a similar question was asked, but received a different answer. In the above question, about changing the color of the grout once it has already been sealed, the answer was “YES”, if you scratch the surface of the grout, it will make a surface that the acrylic paint can stick to, as grout sealer is generally just a “superficial pore sealer”! I hope that helps!

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