Choice: Good casseroles are mostly white in color. White clay is most suitable for cooking food because it has few impurities and will not decompose harmful components after heating. A good casserole has a bright and even surface, no prominent sand grains and no small holes, and it feels smooth. A good casserole is symmetrical, stable on a flat surface and won't shake.
Casserole, generally there will be no impurities into the soup and change the taste. Copper and iron are hard to say, because kebabs have high salt content, or acid or alkali, which is corrosive to copper and iron.
Secondly, the casserole has good thermal insulation performance. As long as there is a small fire at the bottom, the temperature in the pot can be maintained, while copper and iron dissipate heat quickly and need to be kept warm by a big fire.
The pot body of the casserole is not so hot, which can prevent diners from accidentally scalding.