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Hakhsharat Keilim (Part 2)

Rav David Brofsky



As we have seen, a utensil that absorbed a prohibited substance through cooking may be kashered by hagala. Seemingly, hagala extracts the prohibited taste from the utensil. The rishonim discuss whether one need be concerned that the prohibited taste may be reabsorbed into the utensil immediately after extraction or be absorbed into the larger pot within which one is immersing the utensil.


The Shulchan Arukh rules that one should only do hagala to a utensil when the quantity of water is sixty times the size of the utensil, thereby neutralizing the effect of the prohibited taste. Moreover, one may immerse a utensil that is "eino ben yomo" in any amount of water, as the taste that is expelled is "noten ta'am lifgam." The Rema notes that the accepted custom is to perform hagala only on utensils which are "eino ben yomo," thereby avoiding any potential problems. While this is the accepted custom, if waiting twenty-four hours is impossible, i.e., for a wedding in a non-kosher hotel, some permit adding a foul-tasting solution to the water, causing the expelled taste to become "pagum," thereby negating its halakhic impact on other utensils.


A utensil must be prepared for the process of hagala. The Shulchan Arukh notes that one should remove any rust from a utensil, lest there be prohibited matter under the rust. The rust must be removed or subjected to libbun in order to burn away the prohibited substance. As we shall see, libbun kal (see below) may suffice. Some authorities speculate that the lime buildup on some appliances ("kumkums," electric kettles and urns) may be similar to rust.


Similarly, one must also clean all cracks and crevices lest they contain chametz or issur. Where cleaning is difficult, in addition to hagala, the questionable area requires libbun (even libbun kal suffices). Hinged pot covers and attached handles are difficult to clean, and therefore require libbun. Many do not kasher these utensils because of the difficulty involved.


Sometimes, hagala may be difficult to perform because of the size of the utensil. For example, if a utensil is too large to be immersed, the Shulchan Arukh rules that one may immerse half of the utensil, and then the other half. Since hagala is a process of extraction, unlike tevilat keilim, this method of kashering is acceptable.


Similarly, the gemara discusses how one can kasher the rim of a large pot of water. The rim may have occasionally come in contact with food, but the boiling water in the pot cannot reach the very top of the pot. The gemara suggests constructing a rim of cement or clay around the exterior of the pot, thereby raising the height of the pot's walls and allowing the boiling water to overflow and kasher even the top of the rim. Alternatively, the Shulchan Arukh suggests immersing a hot stone in the boiling water, which causes the water to flow over the top of the pot, without lowering the temperature of the water. Similarly, one can heat up a small metal pot over the flame, and immerse it in the water, thereby displacing the water, causing the same effect as the hot stone. As we shall see, libbun kal may also be sufficient for this pot.


As for the process of hagala, most rishonim, as well as the Shulchan Arukh, rule that the principle of "ke-bol'o kakh polto" applies, and a utensil may be kashered the same way in which it was used. Therefore, if a utensil absorbed chametz or any other prohibited substance through irui, i.e., a hot substance being poured onto the utensil, it may be kashered through irui. In other words, one may merely pour hot water from a keli rishon (a pot heated up over the fire) onto such a utensil. Similarly, those who require kashering a utensil which absorbed a prohibited substance in a keli sheni, permit one to kasher this utensil in a keli sheni of hot water. Generally, though, we kasher utensils in a keli rishon of boiling water in case the utensil was ever used in a keli rishon.


Occasionally, however, we do rely upon irui. For example, one may kasher pot handles (assuming one has overcome the above-mentioned problems) through irui, since pot handles are not generally immersed into a keli rishon. Similarly, the Shulchan Arukh rules that one may perform irui on a sink or countertop, as long as it is made of materials that may be kashered. (Some acharonim recommend placing a "hot stone," i.e., a hot brick or a hot metal pot into the sink or over the counter while the water is being poured. By placing a source of heat in proximity to the counter, one raises the level of hakhshara to a level similar to a keli rishon. This is necessary according to those who view all hot pieces of food (davar gush), regardless of their location, as a keli rishon. We will return to this question in a future shiur.


Contemporary authorities discuss the possibility of kashering dishwashers and microwaves based on this principle of "ke-bol'o kakh polto."


The rishonim cite a custom to rinse the utensil in cold water immediately after hagala. While this is the accepted practice, if it was not done, the hagala is still effective.




The gemara (Avoda Zara 75b) states that any utensil which is used over the fire, must be kashered by the fire. Seemingly, we must address the following questions:


  1. What does the process of libbun accomplish? How is it different from hagala?
  2. What is the definition of libbun?
  3. When do we require libbun as opposed to hagala?


The rishonim debate whether libbun DESTROYS the issur absorbed in the utensil, or EXTRACTS it, based upon the principle of "ke-bol'o kakh polto." For example, the Rashba and Ra'ah debate how to use libbun in kashering a utensil which was only partially immersed into a non-kosher liquid. While the utensil was only partially immersed, we may fear that the taste traveled throughout the interior of the utensil. The Rashba (Torat HaBayit Bayit 4 Sha'ar 4) suggests that libbun may be performed only on the area which was immersed in hot liquid, applying the principle of "ke-bol'o kakh polto." If that is how the utensil absorbed the substance, that is how it will expel it. The Rashba clearly seems to view libbun as a form of extraction of issur. The Ra'ah, on the other hand, insists that libbun can only destroy the issur in the area which the fire makes contact with, and in order to destroy the taste which has spread throughout the utensil, the entire keli must be subjected to libbun. The Ra'ah clearly views libbun as an attempt to destroy the issur.


One may suggest that the different interpretations of the parasha in Bemidbar, as explained above, may relate to this question. The commentators seem to debate whether the Torah presents two distinct methods of hakhshara, i.e., passing through fire and passing through water, or one broad principle of "ke-bol'o kakh polto."


This question may also relate to the definition of libbun. The gemara (Avoda Zara 76b) describes libbun as a level of heat which may even peel off the outer layer of the utensil. Similarly, the Yerushalmi describes libbun as a process so intense that it may cause sparks to fly from the utensil. This type of libbun is commonly known as "libbun gamur."


Some rishonim (see Hagahot Maimoniot Hilkhot Ma'akhalot Asurot 17), on the other hand, maintain that merely heating the utensil until heat penetrates through the entire keli - which may be determined by seeing whether a straw or piece of tissue placed on the outside of the utensil burns - is sufficient. This type of libbun is commonly known as "libbun kal."


One may suggest that if libbun is a process intended to destroy the issur, an extremely high temperature should be required. If, however, libbun is also a process of "ke-bol'o kakh polto," merely heating up the utensil should be sufficient.


Rav Yosef Karo rules in accordance with the first opinion, requiring that the utensil become so hot that sparks fly from it. The Rema cites the more lenient opinion, yet rules that one should follow the more stringent opinion.


The Rema, however, seems to endorse the use of libbun kal in a number of situations. Firstly, any utensil which requires hagala may be kashered through libbun kal. This seems to support the notion that libbun kal is based upon the principle of "ke-bol'o kakh polto." Furthermore, for a utensil which fundamentally requires hagala, yet must undergo libbun because of a fear of issur found under rust or in crevices, libbun kal is also sufficient. The Rema also rules that whenever we require libbun "mi-safek," libbun kal is sufficient. The Mishna Berura (451:48) explains that when we require libbun because the minority use (mi'ut tashmisho) of the utensil was over the fire, libbun kal suffices.


Libbun, as mentioned above, is required when a utensil absorbs issur over the fire. While some (see Ra'ah) claim that this is the case only when the utensil was actually used over the fire, most rishonim believe that whenever a utensil absorbs issur without the presence of a liquid, i.e., baking tins and maybe frying pans, libbun is required.


However, the gemara (Avoda Zara 76a) notes that libbun is only required when a utensil absorbs a prohibited substance. However, if a utensil absorbs a permitted substance, such as kosher meat or milk, and one merely wishes to kasher the utensil to change its designation, hagala is sufficient. We will return to this halakha in a future shiur.


The rishonim debate whether absorbed chametz is considered a permitted substance (hetera bala), in which case libbun would never be required, or, based upon its future identity as an issur, is considered a prohibited substance (issura bala) in which case, libbun is at times required. The Shulchan Arukh rules in accordance with the more stringent opinion.


There is no requirement to wait 24 hours before performing libbun.




The authorities disagree regarding the appropriate method of kashering an oven.


Some (Rav Moshe Feinstein zt"l) require libbun gamur. A self-cleaning oven can reach this very high temperature, and therefore one need only clean the oven thoroughly, run the "self cleaning" cycle, and cover the glass door with aluminum. An ordinary oven, however, cannot reach the temperatures require for libbun gamur. Therefore, one can either apply a blowtorch to the walls of the oven, or clean the oven thoroughly and cover the inside of the oven with aluminum foil, or with an insert.


Others maintain that libbun kal is sufficient. Therefore, one must thoroughly clean the oven and then run the oven on the highest temperature for about an hour.


There are two arguments in support of kashering an oven through libbun kal.


Some claim that the primary contact of an oven with food is through steam (ze'ah). The secondary type, or mi'ut tashmisho, is through spills and fallen food. As mentioned above, while we generally require libbun in such a case, because it is only mi'ut tashmisho, libbun kal is sufficient.


Alternatively, some suggest that since libbun may be viewed as a form of "ke-bol'o kakh polto," since prohibited substances may never be absorbed at a temperature higher than the highest setting, that temperature is sufficient to perform effective libbun.


Hakhsharat Keilim from Dairy or from Meat:


Most of the above halakhot apply to kashering from meat to dairy or from dairy to meat. As mentioned above, libbun is not required if the utensil didn't absorb a prohibited substance.


The Magen Avraham (OC 509:11) cites a custom not to kasher utensils from meat to dairy or vice versa. Clearly this minhag is intended to prevent confusion in the kitchen. The acharonim note that when kashering for Pesach, one may change the designation of a utensil (Mishna Berura 452:17). Similarly, when one buys or inherits a utensil one may change its designation. Needless to say, if one inadvertently made a pareve utensil dairy, one may kasher it.


This shiur is intended as an overview of the halakhot of hakhsharat keilim, and we have by no means exhausted the topic. Rabbi Shimon Eider's "Halachos of Pesach" has an excellent section on kashering utensils. Any questions should be brought to a halakhic authority.


Chag KASHER ve-same'ach. 
