Hi Joe, I've read that the best way to clean a tea kettle is with baking soda and apple cider vinegar. Here is a site that gives directions: https://homeguides.sfgate.com/use-apple-cider-vinegar-baking-soda-clean-tea-kettle-105053.html
I just clean my kettle with a little drop of liquid soap and hot water. If the inside of the kettle is stained, you can scrub it with a little bit of salt.
Are you referring to hard water deposits? I recently used Whink and it was by far the easierst experience removing hard water stains. I used it on my hot pot crusty mineral build up and on the underside of my kitchen faucet where the aerator gets crusted and clogged. It worked effortlessly and quickly. I hope this helps!
Boil white vinegar in it
I do same to my coffee pot once each 3 months.
Joe, The inside should be cleaned with white vinegar. Pour some in and let it simmer. Aloha!
Agreed on the vinegar treatment. Just boil the vinegar added to the water and it will take the scum etc, out easily. Then boil it with fresh water before using.