The Pot That Was Not Kashered
A family kashered its kitchen for Pesach. The metal pot used for boiling water was immersed in a larger pot of boiling water (hag'alah) after thorough cleaning, and the family was told by a local supervisor that this was sufficient. On the second day of Yom Tov, a guest notices that the pot had been used that morning to boil pasta (chametz) before being kashered, and that the pot has a small dent near the rim where food residue could lodge. The family had already used the pot to cook kosher-for-Pesach soup for two meals. The guest is a Torah scholar and raises the question of whether the soup and the pot are permissible. The family is distressed and asks whether they must discard the food and re-kasher the pot.
1. Analyze the halachic status of the pot and the food given the dent, the prior chametz use, and the hag'alah performed.
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Framework. Hag'alah removes ta'am absorbed in a kli through contact with boiling water. It is effective only if the vessel is ben yomo (not used with the forbidden substance within 24 hours) or if the absorbed taste is pagum (spoiled). A dent or crevice (sadkin) may retain residue that hag'alah cannot reach; such a vessel may require libun (burning) or milui ve-irui depending on the material.
Application. (1) The pot was used for chametz and then kashered. If the hag'alah was performed after 24 hours from the last chametz use, the absorbed taste is pagum and hag'alah is effective for the smooth surfaces. (2) The dent: if residue lodged there, hag'alah does not reach it. For metal, the remedy is libun chamur (heating to redness) or, if impractical, libun kal. The pot is therefore of doubtful status (safek) as to the dent. (3) The food cooked in it: if the pot was ben yomo or the dent retained chametz, the soup absorbed chametz taste. However, bitul (nullification) applies: the chametz is batel in the soup if it is less than 1/60 and the chametz is not a davar ha-ma'amid. On Pesach, however, chametz is assur be-mashehu - even a trace is forbidden, and bitul does not apply to chametz on Pesach.
Conclusion. The soup is forbidden if there is a reasonable concern that chametz taste was imparted. The pot requires re-kashering with libun at the dent, or replacement. The family should consult the supervisor; the food should be discarded and the pot re-kashered or replaced.
2. Does the principle of 'bitul' rescue the food, and how does the rule of 'chametz be-mashehu' on Pesach change the analysis?
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Bitul generally. In ordinary issur ve-heter, a forbidden substance nullified in 60 parts (bitul be-shishim) is permitted. This applies to mixtures of issur and heter where the issur is not davar ha-ma'amid.
On Pesach. Chametz is treated with unique stringency: the Torah prohibition of bal yera'eh u-val yimatze and the rule that chametz is assur be-mashehu mean that bitul does not operate for chametz on Pesach. Even the smallest amount renders the mixture forbidden. Therefore, if the pot imparted chametz taste to the soup, the soup is forbidden regardless of proportion.
Application. The critical question is whether the pot actually imparted chametz taste. If the hag'alah was effective (pot not ben yomo and dent not retaining residue), no chametz taste was imparted and the food is permitted. If the dent retained residue, the food is forbidden. The beit din/posek should be consulted; the safe ruling is to discard the food and re-kasher the pot with libun at the dent.