It’s no mystery why ceramic tile is so popular: It’s durable, stain-resistant, easy to clean, and impervious to water. Then mix a fresh batch of tile grout (or buy ) and use a to smear it diagonally across the surface and deep into the joints. Wait about 20 minutes, then use a large grout sponge and clean water to wipe off any excess grout. Wait an hour or so and buff the tiles with a clean, dry cloth to remove any residual grout haze. Once the grout is fully cured, apply a silicone-based to increase the water and stain resistance of the new grout joints.