Why do tea and coffee stains build up on mugs over time?Updated 9 days ago
TL;DR: Tannins in tea and coffee slowly build up on well-used mugs. Dishwashing Tabs help with every cycle, and a quick wipe with Universal Cleaner lifts older buildup before the mug goes back in the dishwasher.
Why do tea and coffee stains build up on mugs?
✓ What causes it?
Tea and coffee lovers know the look: a light brown ring that slowly builds up inside a favourite mug. It's common, and it's easy to sort.
Tea and coffee contain tannins, which cling to ceramic and porcelain. Every dishwasher cycle with Dishwashing Tabs helps keep them in check, but with a few cups a day, a thin layer can settle faster than each wash lifts it. Over weeks, that layer builds up into the stain you can see.
How do I clear tea and coffee buildup?
✓ What to do
Spray a little Universal Cleaner inside the mug.
Wipe with a damp Koh cloth or sponge. Older buildup may need a gentle scrub.
Rinse well, then pop it back in the dishwasher as usual.
A quick wipe every other month or so keeps your mugs looking their best. The same wipe works on teapots and travel mugs, and it's worth checking the maker's guidance before a flask goes in the dishwasher.
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Last reviewed: November 2026 · Koh Australia