Every tea drinker has one: the favourite mug that’s brown on the inside no matter how many times you wash it. Those tea stains aren’t dirt — they’re tannins, the same compounds that stain your teeth — and normal washing-up liquid can’t touch them. But a paste of baking soda and water lifts them off in minutes, with zero scrubbing and zero bleach. Your mug comes out looking new.
Why Tea Stains Ceramic So Stubbornly
Tea contains tannins — natural plant compounds that bind strongly to surfaces. Ceramic mugs look smooth, but under a microscope the glaze has tiny pores and micro-scratches from years of spoons and dishwashers. Tannins settle into those imperfections and oxidise over time, turning from a light brown film into the dark, almost permanent-looking rings every tea drinker knows. Washing-up liquid is a degreaser, not a stain lifter — it slides right over tannin stains without breaking their bond to the ceramic.
The Baking Soda Paste Method
- Make the paste. Mix two tablespoons of baking soda with about a teaspoon of water — you want a thick paste, roughly the consistency of toothpaste. If it’s runny, add more soda.
- Spread it inside the mug. Using your fingers or a soft cloth, spread the paste generously over the stained areas inside the mug. Cover every brown ring and patch.
- Leave it for 5–10 minutes. The baking soda needs contact time. It’s mildly alkaline, and that alkalinity slowly breaks the bond between the tannins and the ceramic. For light stains, five minutes is enough; for dark, months-old rings, give it fifteen.
- Rub gently. After the wait, rub the paste around the inside of the mug with a soft cloth or sponge. You’ll feel the stains lifting — the baking soda’s fine crystals provide just enough abrasion to carry the loosened tannins away without scratching the glaze.
- Rinse thoroughly. Rinse the mug well under warm water. The stains should be completely gone. If a faint shadow remains in the very bottom, repeat once — the second round almost always finishes it.
The Salt Shortcut (For Light Stains)
For fresh or light tea staining, there’s an even quicker version: wet the inside of the mug, sprinkle in a teaspoon of table salt, and rub with your fingers or a cloth for thirty seconds. Salt’s crystals are a slightly stronger abrasive than baking soda, so it works fast on light stains — but it’s too harsh for the heavy, set-in rings. Think of salt as the daily driver and baking soda as the deep clean.
What About Coffee Stains?
Same method, same result. Coffee stains are also tannin-based (plus some oils), and the baking soda paste lifts them just as effectively. For coffee stains with an oily film — like the inside of a cafetière or a travel mug — do the baking soda paste first, then wash with hot soapy water to remove the oil residue the soda loosened.
Keeping Mugs Stain-Free
- Rinse straight after finishing. Tannins bond more strongly the longer they sit. A quick rinse when you finish your tea prevents 90% of staining.
- Don’t leave tea sitting for hours. The abandoned mug of cold tea on your desk is staining itself deeper by the hour.
- Run a baking soda round monthly. If you’re a heavy tea drinker, a quick monthly paste treatment keeps your favourite mugs permanently white inside.
- Avoid bleach. It works, but it leaves a chemical taste that takes multiple rinses to remove, and it’s overkill — baking soda does the same job safely.
FAQ
Will baking soda scratch the glaze? No. Baking soda is very soft — much softer than ceramic glaze — which is why it’s safe for this. What scratches mugs is metal scourers and harsh powdered cleansers. A soft cloth with baking soda paste is completely safe.
Does this work on travel mugs and thermoses? Yes, with one tweak: fill the travel mug with hot water and a tablespoon of baking soda, leave it for an hour (or overnight for bad stains), then rinse. The soak does the work where you can’t reach to scrub.
My mug has a crack in the glaze — is this safe? Yes, but stains in cracked glaze (crazing) are harder to remove because the tannins are deeper in the cracks. The paste will lighten them significantly; getting them 100% out of crazed glaze isn’t always possible.
Can I use vinegar instead? Vinegar helps with limescale but it’s less effective on tannin stains than baking soda. For a mug with both tea stains and limescale (hard-water areas), do the baking soda paste first, then a quick vinegar rinse.
If your kettle is looking as tired as your mugs, the same natural-cleaning philosophy applies — see our guide to descaling your kettle with lemon. And for the full tour of what that little orange box can do, browse our 10 baking soda hacks every kitchen needs.