Pushing in grout is rewarding work. But it is also sloppy. Be certain to wear appropriate protective gear for this job, especially rubber gloves, to protect hands from the corrosive effects of cement. A bit of cement on your hands won't kill you, but extended exposure is considered hazardous.
Grout comes in a variety of colors and the quality does vary by manufacturer. Mixing grout is not an art form but takes a bit practice to do it right the first time without having to make adjustments. Grout is a cement product. Normally, it is only mixed with water. But some grouts require an additive. Be sure you follow label instructions closely when mixing grout. The mixed grout should end up being firm and moldable, but not dry and crumbly. Obviously, you can always add a bit more water if the mixture is too firm. Be sure to hold back a bit of the dry powder, just in case you over-do it with the liquid portion of the mixture.
Starting in a corner and working your way toward an exit, dig out a quantity of grout with a wide putty knife and plop it on the tile. With a rubber float, push the grout over the top of the tiles and press it firmly into the cracks. Besides getting grout in the cracks, the object is to get the grout off from the face of the tiles. Make certain that the grout is not uneven or lumpy in the cracks. To even it out, run the corner of the rubber float down the crack. Do not grout the crack between the wall and the last row of tiles. After everything else is done, use silicone caulk on this crack. Caulk will allow for expansion and contraction between the wall and the field of tile - preventing cracks from forming in the grout.
As you work, you will notice a film forming on the tiles. Once the grout becomes firm, using a damp, not sopping wet, sponge, wipe away the film. You may have to do this several times and there will always seem to be a bit left behind until you polish the tile with a dry shop towel.
Some grouts recommend that you wet them periodically (two or three times as the substance dries). This slows down the curing process and allows the grout to set harder. Check the instructions on the box or bag of grout for details.
Wait about two weeks, allowing the grout to fully dry, before putting on sealer. Do this with a foam brush or a special felt tip applicator. Simply apply the sealer to the grout in the cracks, making sure to wipe unexpected swipes from the tile.
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