1. Mix the Grout
Combine the powdered grout and water as specified on the grout packaging and let the mixture sit for about 10 minutes. This process, called slaking, allows the dry power to absorb all of the water. After the slaking period, the mixture should be similar to the consistency of mayonnaise. If it’s not, add a little more powder or water as needed, and let it slake again.
2. Spread the Grout
Hold the grout float at a 45-degree angle to the tile surface and spread the grout into the crevices between the tiles. Make several passes from different directions. Once the joints have been filled, hold the float at a 90-degree angle to the tiled surface and remove any excess grout from the face of the tiles. Work quickly in areas no larger than 3 sq. ft., as grout can harden quickly depending on temperature and humidity levels.
3. Tool the Joints
Drag the rounded corner of the grout float along every joint to create a concave appearance. If you prefer, you can use just about any small rounded object to tool the grout lines; however, don’t use anything metal, as metal edges may damage the tile.
4. Wipe Off Excess
Use a grout sponge and a big bucket of clean water to remove the excess grout from the tile. Wet the sponge and wring it out; then position the long edge of the sponge against the tile and drag it in one continuous stroke across the grouted area. Flip the sponge over and use the opposite clean edge to make another swipe; then rinse the sponge, wring it out and continue the process. You’ll probably need to make two or three passes to effectively clean one area. If a thin film of grout remains, don’t worry — it’s easily buffed out with a soft cloth.
5. Caulk the Edges
Use a utility knife to remove the grout from the corners; then apply a flexible color-matched caulk that will allow for slight movement in these joints.
6. Seal the Grout
Finally, apply a sealer to the grout to prevent it from staining. A rolling applicator that applies the sealer only to the grout makes fast work of this process — if you use a rag or sponge, you’ll need to buff the sealer off of the tile after it dries.
Sealing Porous Tile and Stone
Grout will stain porous tile and stone surfaces such as slate or limestone, and no amount of scrubbing will remove the stains. To protect these surfaces, apply tile sealer before you begin grouting. After you’ve finished grouting, you can leave the sealer on the tile for a wet, glossy appearance. If you prefer a matte finish, follow the manufacturer’s instructions to remove the sealer after the grout has cured.