[header] How to clean grout between floor tiles [title] Make a paste of baking soda and water. [step] Mix 3 parts of baking soda to 1 part water to make a thick paste. This versatile cleaner will work with all colors of grout, but vinegar can be harmful to some natural stones such as marble or limestone. 
[substeps] Apply the paste to the grout lines with your finger. Although the baking soda isn't harmful, wearing rubber gloves can help prevent scratches or irritated skin from the abrasive grout and baking soda.