How do I fix kitchen grout lines that turned yellow from years of cooking oils?

Apply a paste of baking soda and 3% hydrogen peroxide along the discolored lines. The peroxide bleaches organic yellow stains while the alkaline soda breaks down oxidized fats without damaging cement binders.

How can I prevent cooking grease from soaking into tile grout in the future?

Once the grout is clean and completely dry (allow 24 to 48 hours), apply a penetrating, solvent-based or water-based penetrating fluoropolymer grout sealer. The sealer forms a hydrophobic and oleophobic barrier that stops hot grease from penetrating the pores.

Guide

How to Remove Cooking Grease from Grout

Apply a paste of baking soda, warm water, and a few drops of dish soap along greasy grout lines, let it break down lipids for 10 minutes, scrub with a stiff nylon brush, and wipe completely clean with a damp microfiber cloth.

Grout Cooking grease

Context

Conditions that change the method

chemical sensitivity — Never use acidic cleaners (such as vinegar or lemon juice) on cementitious grout, as acids chemically dissolve the cement matrix.

Avoid acids and abrasive metal pads

Porous cement-based grout is alkaline and degrades when exposed to acidic cleaners like vinegar. Metal wire brushes can gouge grout channels and scratch surrounding glazed tiles. Use non-acidic alkaline degreasers and nylon bristles only.

What you need

Baking soda
Concentrated clear liquid dish soap
Warm water
Stiff-bristled nylon grout brush
Clean microfiber cloths
Small mixing bowl

Wipe away loose surface oil and food splatters from the surrounding tile using a warm, damp microfiber cloth.
Mix 1/2 cup of baking soda with 2 tablespoons of warm water and 1 teaspoon of liquid dish soap in a bowl until it forms a spreadable alkaline paste.
Spread the paste generously along greasy backsplash or kitchen floor grout lines using your fingers or a spatula.
Allow the paste to dwell for 10 to 15 minutes so the alkaline soda and surfactants saponify and emulsify deep-seated cooking fats.
Scrub the grout lines firmly using a narrow, stiff nylon brush in back-and-forth strokes to lift dissolved oil out of the pores.
Rinse the grout thoroughly by wiping away all paste residue with a microfiber cloth dipped in clean warm water, then dry with a clean towel.

What to avoid

Never use vinegar, citric acid, or acidic bathroom cleaners on cement grout, as acids cause crumbling and pitting.
Do not use steel wool or metal wire brushes, which scratch tile glazes and leave rust-prone metal specks.
Avoid leaving dried baking soda film on textured tiles; rinse completely with clean water.

Products

What to use

Related guides

FAQ

Questions people ask

How do I fix kitchen grout lines that turned yellow from years of cooking oils?: Apply a paste of baking soda and 3% hydrogen peroxide along the discolored lines. The peroxide bleaches organic yellow stains while the alkaline soda breaks down oxidized fats without damaging cement binders.
How can I prevent cooking grease from soaking into tile grout in the future?: Once the grout is clean and completely dry (allow 24 to 48 hours), apply a penetrating, solvent-based or water-based penetrating fluoropolymer grout sealer. The sealer forms a hydrophobic and oleophobic barrier that stops hot grease from penetrating the pores.

Sources

Cleaning Grout — Tile Council of North America
Food Safety Basics — U.S. Department of Agriculture Food Safety and Inspection Service