“Question: When I kasher utensils to use on Pesach, should I kasher in a Pesach pot or chometz pot? And what about the kettle that I use to kasher the sinks – should I use the Pesach kettle or the year round kettle?
Discussion: The Shulchan Aruch (Orach Chayim Siman 452 se’if 1) writes that one should attempt to kasher before the fifth hour (i.e. before sof zman achilas chometz) in order to avoid ensuring that all utensils being kashered are eino ben yomo and to avoid having to kasher the pot that is used for hagoloh before and after kashering other utensils inside it.
Namely, if one kashers before sof z’man achilas chometz then one can use a chometz pot to kasher with, and the only situation in which one would need to use a Pesach pot to kasher with is if one kashers after sof z’man achilas chometz.
The Mishna Berura (Siman 452 s.k. 10) explains the reason for this distinction:
• Before sof z’man achilas chometz there is no need to kasher the pot used to kasher with, because at this stage the chometz bliyos that the pot emits are classified heter and consequently the water inside the pot is referred to as nat bar nat d’hetero.
This means that since chometz at this stage of time is classified heter, therefore the original chometz bliyos in the pot are termed nat rishon. Subsequently, the water heated up inside the pot is termed nat bar nat of heter (because the water absorbs the nat rishon taste that was absorbed into the pot and becomes nat sheni or nat bar nat d’hetero). In contrast to nat bar nat that originates from issur, nat bar nat d’hetero is permitted (see Yoreh De’ah Siman 95) and it is therefore acceptable to kasher inside this water.
• However, after sof z’man achilas chometz the bliyos of chometz inside the pot are classified issur and consequently the water inside the pot becomes forbidden. This is because regarding issur even many transfers of bliyos will not diminish the issur status and therefore the chometz bliyos absorbed in the pot will prohibit food cooked inside the pot, which is now technically classified nat bar nat d’issuro. Consequently, if one heats up water inside this pot, the water inside the pot becomes prohibited, and therefore the utensils being kashered in this water will also become forbidden, and hagolo in such a pot is completely pointless.
There is another significant point that must be discussed: The Bi’ur Halocho (Siman 452 se’if 1 d.h. “she’ein”) writes that the distinction of the Shulchan Aruch between before and after sof z’man achilas chometz is only relevant according to those authorities who maintain that chometz during the year is termed “heter”. However, several Poskim (Olas Shabbos, Pri Chodosh and Vilna Gaon) and the Shulchan Aruch himself in Siman 451 maintain that chometz even during the year is classified as issur and therefore there is no room for leniency even before sof z’man achilas chometz. Therefore, the Bi’ur Halocho advises one of the following options:
• To ensure that all utensils [i.e. those being kashered and those being kashered in/with] are eino ben yomo
• To kasher the utensil that one wishes to kasher other utensils inside of, and to ensure that there is sixty times the volume of the utensils being kashered in the water.
Practically, the first option is easier to implement. It is therefore generally advisable that when one wishes to kasher for Pesach (or from other issurim), they should ensure that all utensils (those being kashered and those being kashered in/with) are eino ben yomo.
Conclusion: When kashering utensils for Pesach (before sof z’man achilas chometz) one can use a clean eino ben yomo chometz pot to kasher with.
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