1-Fresh Lemon Juice
I scrubbed the grout lines with a slice of lemon before giving it a good scrub with a green Scotch-Brite pad. I noticed an immediate improvement in cleanliness. I then rinsed the grout lines with a damp paper towel. The only cumbersome aspect of this method was removing the leftover pulp. Once dry, the grout looked substantially better.
2-Oxiclean
I prepared a small quantity of Oxiclean in a plastic cup, maintaining a 1-to-1 ratio to form a runny paste. Using an old spoon, I applied this mixture to the grout, ensuring constant stirring to prevent the Oxiclean from separating from the water and hardening. After letting it rest for 5-10 minutes, I scrubbed it with a Scotch-Brite pad. This method was quite effective, but the Oxiclean did leave a white residue on the floor, necessitating immediate rinsing with water and thorough mopping afterward.
