earthenware

Does an earthenware vessel swallow and not spit out? Or does it spit out only part of it? Because if it swallows and not spit out, then if it is apparently prey, it does not need to be made pure even by using hot or spicy food or by cutting with a knife despite the pressure of a knife. And are what are called earthenware cups today really earthenware, or is it covered with a porcelain covering? And what is the ruling here too, when these cups are made with only the outer circle made of earthenware, on which some sharpen knives?