Cheres - Porcelain

QUESTION: What is the status of porcelain? Since it is made from clay, is it considered cheres, or perhaps since it has glass-like qualities, it is more similar to glass?

ANSWER: Rav Yaakov Emden (Shailas Yaavetz 1:67) writes that he heard from his father, the Chacham Tzvi, that porcelain is classified as a type of glass. This is because porcelain is hard and smooth just like glass. Porcelain is translucent like glass as well. Nevertheless, he writes that due to the stringency of Pesach, the minhag is not to kasher used porcelain for Pesach, but rather to purchase new dishes. The Pri Megadim (MZ 451:31) writes that the Kineses Hagedola and Pri Chadash both disagree with the Chacham Tzvi and write that porcelain should be considered full-fledged cheres. The Mishnah Berurah (Beiur Halacha 87:1) as well cites the ruling of the Pri Megadim that porcelain cannot be kashered. Igros Moshe (YD 2:46) writes that although the ruling of the Chacham Tzvi was not accepted, in a difficult situation, when there are other mitigating factors, this opinion can also be considered.

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