Ultimate Grout Cleaner is the best grout cleaner for tile and grout cleaning, it is an innovative, labor saving cleaner for grease, dirt, oil and soap scum on white or colored grout. This acid-free formula provides you with the best way to clean grout and ceramic, porcelain or marble. It can also be used for cleaning grout with a grout steam cleaner. Because it is acid-free it will NOT clean calcium or water spots from showers but it will work extremely well on the soap deposits. It will not normally etch marble but we always recommend that you do a test area first. Simply spray on the grout or tile and let stand for 1-3 minutes. Agitate with a brush to loosen embedded soil. Rinse with clean water. This product is very strong so do not use on painted surfaces. Made in the USA.