6. Let the grout set up for about 30 minutes, then gently remove the grout from the face of the glass with a damp sponge. Rinse the sponge frequently. When the grout dries, buff your new backsplash with a soft cloth to remove any remaining haze from the grout. Use a grout sealer (we used AFM Safecoat Grout Sealer) to protect your new mosaic.