Use hydrogen peroxide. Need a recipe? Mix together 1/2 cup of baking soda, 1/4 cup of hydrogen peroxide, and 1 tsp dish soap. Apply cleaning mixture onto the grout, wait...
Mix one tablespoon of lemon juice or vinegar with one scant cup of milk and let stand at room temperature for 5-10 minutes. The mixture will thicken into small curdled...