Tile regrouting. Freshening a tile surface.
In time, the grout between tiles may become mildewed or soiled or may crumble, allowing water to penetrate. Using a sharp-bladed tool, such as an awl or an old. thin chisel or screwdriver. scrape out loose and marred grout. It’s not necessary to get out all the old grout: just make sure that what’s left is clean and solid. Wipe off the powdery residue with a cloth.
Mix fresh grout as specified on the container (it comes as a powder you mix with water) and apply it over the scraped areas with a rubber squeegee or with your fingers. Wipe grout from the tiles with a damp sponge. Let the grout thy for at least 12 hours; then polish with a piece of clean, dry burlap.