Here is a write up I did on them Austere Provisions Company Klean Kanteen Blog Entry
After a few days of boiling gallons of water each day I took them back and scrubbed them down to get the soot off. Inspection revealed no discernible damage or weakening of the metal.
I have used it on charcoal, camp stoves, and an electric range eye still with no damage or weakening visible to the naked eye.
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