I use Bar Keepers Friend cleanser, I shake out the cleanser on the bottom of the pan and add just enough water to make a paste. Once it is that consistency I let it sit for 15 minutes. Then I use a no scratch scrubber to remove anything that’s still on the bottom of the pan.
Try covering it with baking soda and then pour some vinegar over it. Let it work and then wash with soap and water.
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