READ: Why your wine glasses smell weird and how to fix it
The dark brown stain in your mug or cup is brought about by tannins. Tannins are plant compounds found in tea and coffee (and some other foods and drinks) and are what give these hot drinks and beverages their distinctive, slightly bitter flavour.
Tannin stains show up and remain longer on white or light-coloured ceramic mugs. If you’re a lover of hot drinks, this unpleasant sight might leave you frustrated wondering just how to remove tea and coffee stains from mugs.
