IT'S ABOUT TIME FOR THIS TEAPOT TO BE RESCUED
IF YOU ARE GOING TO USE MY WAY OF CLEANING THE TEAPOT PLEASE TAKE CARE. FOLLOW THE INSTRUCTIONS VERY CAREFULLY. USE GLOVES AND WASH THE TEAPOT WITH PLENTY OF WATER BETWEEN STAGES.
Sometimes a teapot can reach this state, you wash it in the dishwasher and still looks like this.
My way is very simple and efficient
Pour a bit of bleach into the teapot
Add to the bleach hot water
Let it soak until you no longer see the brown marks
Rinse the teapot very, very well with plenty of water. To be on the safe side you should wash it in the dishwasher to remove any remains of the bleach
DO NOT throw away the bleach after you finished cleaning your teapot. Save the Planet and money. Use the bleach to wash floors/toilets or better still to soak your tea towels in order to remove any stains ( PLEASE USE GLOVES when moving the tea towels from the sink into the washing machine )
After all that washing sometimes you still can see some watermarks on the bottom of the teapot, if that is the case ( remember to rinse very well before you go to the next stage)
Pour a bit of vinegar and let it soak for a bit
Rinse it with plenty of water.
Now you have a teapot free of stains and watermarks