"Our sages teach us that porcelain, china, or stoneware dishes can not be kashered because once a "treif" substance is absorbed into them it can never be expelled. It just remains there and can not be eliminated by any process. Hence the dishes must be discarded."

Hmm. The whole point of a glaze on dishes is to *stop* stuff being absorbed into them. This judgement makes perfect sense for porous clay pots, but seems a bit of an oddity for modern (as in hundred years or so) ceramics. Not to criticise, but just wondering why.

Graham.