Grout is Your Friend
"Grout is your friend." My motto! Grout color is super important and is a common question people ask me with regard to their project. Your grout color should pull everything together and not interfere with your design. Here's what I learned from other experts: white grout fractures, black intensifies, and gray blends. So choosing your color depends on the effect you are going for.
White grout is great for white broken dishes and areas that you want to keep a bright white color. However, any errors you make are accentuated by white. Black works well when you use lots of bright colors in a mosaic but it can also overpower your piece, and gray is always a safe choice. Not easy to choose, huh? If you are unsure of which color, sprinkle some dry grout powder into your mosaic and see if you like it. After you decide, you can then brush it out. Remember, the color you see when it is a dry powder is the color it dries back to.
I recommend using sanded grout with polymers as they help strengthen your mosaic. Mapei, Laticrete, are two brands that are good, but there are more as well. Check with your local home improvement stores like Lowe's and Home Depot, etc...
When you mix your powdered grout, start with a tiny amount of water in the bottom of your container, then slowly add the powder. A little water goes a long way! Keep adding both until you obtain that "peanut butter" consistency. After you mix your grout, let it sit for about 5-10 minutes so the chemicals will have time to work.
If possible, try to buy a grout that is already the color you like. If you can't find one, I recommend Tints-All. It is a colorant that is very concentrated and a few drops added to your white or grey grout will provide a nice, rich color. You won't achieve this with adding acrylic paints.
After you have spread your grout (using a float or your gloved hand, or other spreading device) on your piece and removed the excess, let it sit a few minutes. Then I recommend using the dry-method to clean your mosaic. Using clean, dry rags, gently wipe the tops of your tesserae, while moving your rag to a clean spot so you don't "drag" the grout around. Continue this process until you have a nice, clean mosaic. Let it sit for 24 hours, then wipe with a wet cloth or sponge. If you see any grout "haze" use vinegar and water and lightly rub on top to remove the haze and shine up the tiles.
Grout really is your friend – it pulls your colors together, hides flaws, and creates a long-lasting work of art. If you want to see me doing it, there are some inexpensive videos you should check out here.