According to Mapei Corporation, the Milan-based company that manufactures it, Keracolor grout is a Portland cement tile grout that comes pre-mixed, requiring only the addition of water before use. The company makes both sanded and unsanded grout, and the unsanded variety is for use with tile joints less than 1/8 inch wide. The grout looks best when the tiles are properly installed on a stable and level surface and uniformly spaced.
Lay the Tiles
Fiber-cement backing board provides a solid, waterproof substrate and is best for walls and floors, especially in damp locations, such as kitchens and bathrooms. Waterproof drywall -- or greenrock -- is also suitable for walls out of direct contact with water, and 3/4-inch plywood is the surface of choice for countertops. Be sure the joints between plywood sheets are filled and sanded flat. In the case of fiberboard and drywall, the joints should be tapped and mudded or mortared. When tiling over an area that has been previously tiled, remove all the old adhesive by chipping or sanding.
When laying tiles in a regular grid patterns, locate the center of the wall, floor or countertop, draw a cross, and lay four tiles on the cross, using spacers to keep them uniformly distant. Work outward from there, cutting tiles on the edges of the surface as needed to make them fit. This method works for tiles of all sizes. If a stagger pattern is desired, center one tile on the cross and lay a line from that point to the edges. Set the tiles on either side of the line so that the joints between them line up with the centers of the tiles on the line.
Apply mastic or thinset mortar to the substrate with a notched trowel and set the tiles in the adhesive. To get the most attractive grout lines, use spacers to ensure the joint spacing is uniform.
It goes without saying that before you apply the grout, all the tiles should be securely stuck to the substrate, and the adhesive should be dry. It can take tile adhesive 24 to 48 hours to set completely, so check the specifications for the product you're using. In addition, it's important to complete the following procedures before grouting:
- Verify the gap. If it's more than 1/8 inch wide, use sanded grout.
- Remove the tile spacers and chip out any hardened adhesive with a chisel.
- Seal the tiles if they are porous. Unglazed ceramic, stone and terra-cotta tiles are especially prone to staining if they aren't sealed. Porcelain tiles usually need no sealer.
- Wipe up excess water. The grout won't adhere if any standing water is present.
- Clean off all dust with a rag.
Preparing the Grout
To avoid color variations, it's best to mix all your grout at the same time. If you have to make more than one batch, carefully measure the amount of grout and water so you can use the same quantities for the next batch. The mixing ratio recommended by the manufacturer is 4.8 to 5.4 U.S. ounces of water for every pound of powdered grout and 24 to 27 U.S. ounces for every 5 pounds.
Measure out the water in a container; then slowly pour in the required amount of powder, stirring with a low-speed mixer for 3 to 5 minutes until the grout has a uniform consistency. Let the grout sit -- or slake -- for about 5 minutes; then mix again immediately prior to using it.
Applying the Grout
The ambient temperature should be between 50 and 100 degrees F when you apply Keracolor grout. Wipe the tiles with a damp sponge; then apply the grout with a rubber float. Swipe diagonally across each joint to ensure it's completely filled, with no voids; then run the edge of the float along the seam to remove the excess. After you're finished, the level of the grout should be flush with the surface of the tiles.
Give the grout about 15 or 20 minutes to firm up; then fill two clean 5-gallon buckets with water. One bucket of water is for rinsing off the sponge, and the other is for getting it wet again. Get the sponge damp, but not dripping wet, and wipe it diagonally across each grout line to remove haze from the surrounding tiles. Rinse the sponge often in the rinsing bucket, and get it wet again in the other one after rinsing. Avoid using too much water or excessive pressure, or such defects as efflorescence, powdery joints, and discoloration may result.
Allow the grout to set for an hour or two after the initial cleaning; then go back, if necessary, and clean again with a sponge and water. As a final cleaning -- when only a small amount of haze remains -- rub down the surface of the tiles with cheesecloth.
If you're grouting a floor, don't walk on it for 72 hours after applying the grout. Avoid impacts to wall and countertop tiles for 14 days after grouting.
Protect grout in heavy-use areas, such as floors and bathroom and kitchen counters, by applying a sealer. A clear, penetrating polyurethane or acrylic sealer generally provides optimal protection without affecting grout color.