A guest mistakenly used a dairy porcelain bowl for hot meaty cholent. We intended to set-aside the bowl, but our housekeeper cleaned it, and placed it among five other identical bowls. Now, we do not know which of the six dairy bowls was used for the cholent. What do we do?
Answer:
In this case the treif bowl is battel (null) among the other bowls, and there is not need to take further action.
Because of the possibility that porcelain today is considered as glass, and the possibility that glass requires and can be kashered (some Ashkenazi authorities rule this way; according to this the bowl will be a davar sheyeish lo matirin), it is preferable to perform hag'alah on the bowls. If this cannot be done, they can be filled with hot or warm water for three days, the water being changed every day.
Best wishes.