I scrubbed my bathroom grout with three different store-bought cleaners before I gave up and made my own. The store stuff left the grout a slightly lighter shade of brown. My homemade paste turned it back to the original off-white. My wife thought I had re-grouted the floor.

The secret is baking soda and hydrogen peroxide. Together they create a paste that lifts out the grime that spray cleaners just push around.

The Paste Recipe

Mix half a cup of baking soda with just enough hydrogen peroxide (the 3% kind in the brown bottle) to make a thick paste. It should be the consistency of pancake batter — spreadable but not runny. Add a few drops of dish soap to help it stick to vertical surfaces.

How to Apply It

Use an old toothbrush to work the paste into the grout lines. Really get in there — scrub back and forth along each line, not in circles. Let the paste sit for ten to fifteen minutes. The baking soda scrubs while the peroxide bleach-oxidizes the stains.

Wipe up with a damp cloth, then rinse with plain water. For really deep stains, do a second round immediately. The grout will lighten even more on round two.

For Really Bad Grout

If the baking soda paste is not cutting it, try oxygen bleach powder (like OxiClean) mixed with water into a paste. Apply the same way. Let it sit longer — thirty minutes. This stuff is stronger, so do a test patch first and wear gloves.

Seal It After

Clean grout re-stains fast if you skip this step. Buy a grout sealer — the kind in a squeeze bottle with a brush tip — and run a bead along every line. Let it dry for 24 hours before the floor gets wet. Sealed grout repels water and dirt, so your next cleaning is just a quick wipe instead of another hour of scrubbing.