When normal cleaning procedures are not enough, then you have to get tough ��_��__��_��__��_��__ and this does the job! This industrial strength acid cleaner will remove embedded mineral deposits and carbonaceous soils such as rust, calcium, urine stains, soap scum, grout haze and efflorescence from manufactured tile and cement grout. Can be used to etch hard-to-clean grout by removing a super fine layer, leaving your grout sparkling bright and clean. Advanced formulation with premium chemistry and corrosion inhibitors. Not recommended for use on most natural stone.