This article is about coloring grout for mosaic art before the grout is applied.

This article isn’t about staining grout for bathroom backsplashes. From what I’ve read, staining bathroom grout doesn’t tend to last but has to be refreshed within a year or two. If I wanted to change gout color, I would remove the existing grout with a grout removal tool and then re-grout.

Another problem with grout stains and concrete dyes is that they tend to be limited in color, especially what is available at your local building material store.

Coloring Grout With Acrylic Paint

White grout (for dry indoor mosaic art*) can be colored with artists acrylic paint. You should mix the grout up according to manufacturer instructions, and once you have a nice lump of grout with a consistency similar to dough, you can add the paint. Mix in the paint a little bit at a time until you work up to the color you want. (It’s easier to add than remove, as my father would say.)

Make sure you use white grout because white will be easiest to color. If you find that you can’t get a dark enough color with white grout, then consider starting with grey grout. However, if you start with grey grout, you may find it easier to get a darker color, but it might be less intense than what you got with the white grout.

*Outdoor And Wet Mosaics

I’ve not used this on wet mosaics. That doesn’t mean it cannot be done. It only means you should test first and be aware that not all pigments are UV resistant and can fade with prolonged exposure to sunlight.

Testing For Outdoor Use

I would test my colored grout by placing a hardened lump in water for a week and look for signs of color leaching or softening. I would use a minimal amount of water and look to see if the water was tinted after a week of soaking.

I would also make a few other lumps for hammer hardness testing. I would have a few control lumps with NO paint added so I could compare their hardness to the experimental specimens. Place the head of the hammer in your hand and press down on the sample with increasing weight until it crumbles. The specimens with paint should be more resistant to crumbling. Definitely email me if you observe anything different.

Use Studio Grade Pigments For Reds, Oranges And Yellows.

Use studio-grade or student-grade pigments when it comes to reds, oranges and yellows. The artist-grade pigments of reds, oranges and yellows are cadmium oxides, which are toxic. Studio-grade pigments are generally “non-toxic,” which means there isn’t a known toxic effect in the short term.

Acrylic Paint Strengthens Grout

Acrylic paint should improve the tensile strength and impact resistance of the grout the same way thinset is fortified with polymers. Of course, all of this refers to conventional grout and not the new epoxy-based grouts. I have no idea what could be done with epoxy grouts.

Should You Color Grout?

The most important question about coloring grout is should you color it.

Consider the following:

Novice artists tend to see the choice of grout color as an opportunity to improve their mosaic. Experienced artists tend to see grout color as a potential to screw up their mosaic and thus tend to make a conservative choice for grout color,

Grout color should contrast tile colors not match them. Unless you are using gray tile or light blue tile, a medium gray is usually the best choice of color because it tends to contrast the most colors. If you match grout color to tile color, then your tiles won’t be separated visually, and the mosaic effect will be lost.

The grout line is best used to separate the tiles visually and not as a color field. Think about how a thin pencil line provides definition to watercolor paintings but not color. That is how grout is best used.

Wrong Color Grout?

If you realize that you chose the wrong color grout, I wrote an article on fixing grout mistakes, including wrong colors.

Test Color Of Hardened Grout Before Applying To Mosaic

Of course you should test the color of your mix before applying the grout to your mosaic. By test, I mean mix up a small amount of grout and color it and allow it to harden overnight. You need to know what the grout looks like when it is hardened and dry before you even consider applying it. Keep in mind that grout always looks less intense and lighter after it has hardened.

If you are worrying about wasting a little grout and paint by testing it in this way, then consider how much you will waste if you apply it to your mosaic and it isn’t right…