What pot can never be made kosher?

Shalom, Thank you for your question. I’m not sure exactly what you are asking. However, perhaps you are asking about how to kosher pots and pans used for non kosher cooking. If so, then in general all types of pots can be koshered (each in a different way, according to the material the pot is made of, and the way it was used to cook the food in) – but earthenware cannot be koshered in any normal process. But, even with earthenware (clay, pottery, china etc), there are certain leniencies depending on the situation. In some cases there are ways to kosher even such pots. But, as I said, in general these materials are not koshered at all. Please feel free to get back to us with any more questions. Blessings.