The light color on the underside of the porcelain stoneware in the first photo is the original, untreated porcelain stoneware. On the second photo is already seasoned interior. This is to prevent food from penetrating the stoneware and make the stoneware even easier to clean. This process requires the pottery to be placed in a 450 degree kiln, which is why it has withstood it. A pot full of water will (eventually) boil at a high temperature, but not at a low temperature (hopefully that's the "boiling temperature"). So it could be perfect for bone broth. I'm reluctant to try it on the stovetop, but when I do I start at the lowest temperature and increase slowly to avoid cracking. Yes, and the insert is some kind of rock, not clay (as some reviewers wrote).
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