Cleaning and sealing tile grout
yes, if your tile grout is light colored and the dark areas are of an organic makeup (coffee, gravy, etc.), bleach will clean and brighten the grout. I believe it is applied full strength with a paint brush and allowed to soak-in for several minutes. Agitating with a stiff bristle brush will loosen any surface stains. Wipe up remaining bleach with a dry rag and than wipe with a rag that's been lightly wrung of clean water. Dry with a towel.