Lo Basi Ella L’orer: Waiting 24 Hours To Do Hagalah

Ordinarily, we require waiting 24 hours before doing hagalah on utensils that had absorbed non-kosher. This is because before 24 hours the ta’am that is absorbed inside of a utensil is still nosain ta’am lishvach. The water that one tries to use to kasher the utensil will receive the non-kosher ta’am and it itself will become non-kosher. The utensil will reabsorb this water and the utensil will remain non-kosher. After 24 hours, the ta’am inside the utensil is nosain ta’am lifgam and will not make the water non-kosher. Even still, it is our practice to deal with the water as a lichatchila situation, and we require that the water be discarded. (In cases of need there are methods of kashering ben yomo utensils with a davar hapogem.)

How do we know if a utensil is an aino ben yomo? Can we rely on the rule stam kailim aino ben yomo?

Rav Belsky explains that it is not simple to apply this rule in a factory type setting. Stam kailim aino ben yomo is based on a sfek sfeika. We don’t know whether the utensil was used with issur in the past 24 hours, and even if it was used with issur maybe that issur is pogem the heter that will now be cooked. In our average factory environment, we know what the issur was that was used in the utensil. We know if it is pogem the heter or not. The only thing we don’t know is whether the utensil was used within 24 hours. This is only one safek. If we don’t know for sure if the equipment was used with issur since the last time it was kashered then we would have a valid sfek sfeika and we can kasher the equipment.

We start counting the 24 hours from the last time the utensil was used with hot, or in the case of kavush, from the last contact of the utensil with the kavush liquid. One should keep in mind that jacketed kettles have non-kosher water kavush in their jacket. One must wait 24 hours from after the water is drained unless a davar hapogem is used.

If the company cleaned the utensils with hot water, and no davar hapogem was added, then one may have to wait 24 hours from after this cleaning.1 Ideally, a mashgiach should inspect the utensils 24 hours before kashering to verify that they are not being used and have already been cleaned and will be an aino ben yomo at the time of kashering. If the utensil might have been cleaned more than 24 hours ago, and might have been cleaned with a davar hapogem then the classic sfek sfeika of stam kailim would apply. Maybe it was used more than 24 hours ago, and even if it was used more recently maybe it was used with a davar that is pogem.

Can we rely on non-Jewish workers that are maysiach l’fi tumam?

We do not rely on a non-Jew that is maysiach l’fi tumo by issurim d’orasiah. Therefore, if the utensil had been used with issurim d’oraisah, we certainly cannot be lenient. If the utensil was only used with issurim d’rabbanan then the Gr”a (Y.D. 122:32-33) says that this is dependant on two opinions brought by Rema there. Lichatchila Rema says that one should be machmir not to rely on a non-Jew that is maysiach l’fi tumo. Bishas Hatzorech, the Rema says that one can be lenient. It should be noted, that it is not always easy to get information from a non-Jew in a manner that will be considered maysiach lifi tumo.

If the equipment is attached to Taylor charts or products are stamped with date codes, which are done because of government regulations, then this can be relied upon to show us if the equipment was not used hot in the past 24 hours. Rav Belsky said that log books of companies that are very organized and are always found to be accurate can be relied upon bishas hadchak.

If a mashgiach is uncertain if a utensil is an aino ben yomo, then he should kasher it with a davar hapogem or wait.


  1. Under normal circumstances one must wait until a utensil is an aino ben yomo before doing hagalah.
  2. Ideally a mashgiach should inspect the equipment 24 hours before kashering
  3. One cannot always rely on the rule stam kailim aino ben yomo before kashering
  4. We count the 24 hours from the last time the utensil was used hot (or kavush)
  5. One cannot rely on a non-Jew maysiach lifi tumo in regards to issurim di’oraisah
  6. One can rely on Taylor charts, but should only use log books of organized companies and even then only bishas hadchak.


1 If it was cleaned with plain hot water then there are several variables that will affect whether we need to restart the 24 hour clock. Was it a ben yomo at the time it was cleaned? How dirty was the utensil? How much water was used? Was it cleaned with an irui kli rishon or as a kli rishon itself?

OU Kosher Staff