Grout color is important.
Beside protecting the mosaic, grout has a visual function. Just like the frame of a painting brings attention to it, grout is there to get people’s attention to the actual tiles. There are many theories about how you should use various colors to achieve different visual effects
Here is a good article by Big Picture Mosaics exploring different options on this matter.
Personally, I believe grout should contrast, and not match, the color of the tiles. Without sufficient contrast, they will blend together and you’ll lose the specific aspect of mosaics.
You can have any color as long as it’s black
After having experimented with various colors, I set my heart on dark bright grouts (Red, browns), and I definitely use black grout in 95 % of my mosaics.
Can you find really black grout ?
Unfortunately you can’t !
No commercially available grout is black enough. Some black sanded grouts are really black, but these are to be used for actual floor tiles. The gaps between mosaic tiles are too small for these. And for some reason the unsanded grouts you can find on the market are not black and not even dark grey.
You can purchase “Charcoal” grout of excellent mechanical properties, but once it’s dried up its color will be of a medium dark grey.
Making really Black Grout ?
Fortunately, there are ways to make much blacker grout !
DIY and online stores carry concrete stains that come either in liquid or powder forms.
I tried both…
Powders are better !
Liquid may be a little easier to handle, but they do not allow for consistent results, and they are less powerful than the powders. Powders being very thin, sticky and messy, you should avoid getting them on your hands or cloth for they are very hard to clean up. But they will do a much better job than liquid stains or acrylic paints.
Mixing your grout
So basically what you do is mix your grout as usual and add a small quantity of the powder to it. DO NOT OVER DO IT, remember: this is a color; it has no adhesive ability, and adding too much of it will weaken your grout – I generally use a teaspoon of black powder for a pint (1/2 liter) of grout. Mix it thoroughly, make sure the po0wder is well distributed in your grout, and you will soon see your grout become much darker.
Once dry, your grout will be much darker than if you had not added the powder to it. Here is a picture of 2 samples I made last week for the sake of this article, the difference is obvious.
There are other things you can do to get your grout to look darker, and I will address them in future articles, but really, this is where you should get started.
Have a nice September !