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Black Spots Remaining After Self-Clean Kashering of an Oven

Question

After kashering an oven with 2 hours of self-clean, there are black spots that do not wipe off like ashes, look too black to be ashes, and look the same as before the self-clean. Is it still okay?

Answer

It is fine.

Sources

The Arukh HaShulchan writes that before kashering, a utensil must be cleaned of rust, but only rust that has real substance (mamashut). Mere blackness (shacharut b’alma), or a reddish tint, where the mark remains even after the rust is removed, is not a problem. He gives the reason, citing the Taz: otherwise you would hardly find any utensil that could be kashered. Black spots that do not wipe off and look the same as before are this kind of residual discoloration, so the kashering is fine.

  • Arukh HaShulchan, Orach Chaim 451:12 — only rust with substance must be removed before kashering; mere blackness or discoloration that remains after cleaning is of no concern (citing Taz 451:6)

Author

Rabbi Shay Tahan

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