Clean porcelain tile with an alkaline-based tile and grout cleaning solution. Do not use household cleaners, as they can be absorbed by the tile and leave a residue that can build up over time.
Mix the alkaline cleaning solution with hot water and apply this mixture directly onto the porcelain tile with a sponge or mop. Let this solution sit on the tiles for about 20 minutes. During this time, scrub the tiles and grouted area with a scrub brush. If the finish is delicate, use a soft scrubbing pad to avoid scratching the surface. After scrubbing and when 20 minutes have passed, rinse the area completely with clean water.