Grout is the most neglected surface in most homes - and the one that makes the biggest visual difference when it's clean. Here's the professional approach.
Grout is porous. It absorbs moisture, soap residue, body oils, and airborne grease from cooking. Standard cleaning with a mop or spray barely scratches the surface.
Step 1: Make a paste of baking soda and water (roughly 3:1 ratio). Apply generously to all grout lines.
Step 2: Spray white vinegar over the baking soda paste. Let it fizz and work for 5-10 minutes.
Step 3: Scrub with a stiff-bristled grout brush (not a sponge - you need stiff bristles to get into the pores). Work in small sections.
Step 4: Rinse thoroughly with clean water. Dry with a clean cloth.
For badly stained grout: oxygen bleach (Oxiclean) mixed with water is far more effective than chlorine bleach and safer for colored grout. Apply, let sit 15-30 minutes, scrub, rinse.
Mix 1 part bleach with 2 parts water. Apply with an old toothbrush, let sit 10 minutes, scrub, rinse well. Ensure good ventilation. Never mix bleach with anything except water.
Seal your grout annually with a penetrating grout sealer. This dramatically reduces how much dirt and moisture the grout absorbs, making future cleaning much easier.
If grout is severely discolored, cracked, or has extensive mold penetration, professional cleaning equipment (hot water extraction, commercial-grade cleaners) gets results home methods can't match.