Gather supplies. I chose a large canning pot since I had a teapot I was polishing.
Tear off a piece of tinfoil.
Crumple up tinfoil.
Put tinfoil into pot of water.
Bring water to a rolling boil.
Add baking soda to boiling water. I used approximately 3/4 cup since I had such a large pot.
Carefully place piece in water. I submerged this teapot.
I let it sit and boil for approx 20 minutes. Use tongs to take out of boiling water.
Before & After.
Done! *Note: This was not an heirloom piece, so I was completely comfortable doing this. (I would recommend hand polishing an heirloom.)