Shiur #22: Crock Pots, Hatmana inside other Food, and Insulation in a Thermos

  • Rav Yosef Zvi Rimon



By Rav Yosef Zvi Rimon



Shiur #22 – Crock Pots, Hatmana inside Other Food, and

Insulation in a Thermos



May one put a bag of rice in cholent?


Is one allowed to put hot water in a thermos on Shabbat?


May one use a crock pot on Shabbat?




Netina and Shehiya


A crock pot (slow cooker) has an outer shell with a heating element and a ceramic insert.  Food is placed in the insert in order to cook or heat it.  On Shabbat itself, obviously, it is forbidden to put a vessel with food inside this device, since this is a vessel normally used for cooking and it is not swept or sprinkled.  However, what about cooking food in it before Shabbat? 


In relation to the prohibition of shehiya (retention), if the dish is cooked to the level of ma’akhal ben Derusai (minimally edible) or totally uncooked, there is no prohibition of shehiya.  Similarly, if we take out the knobs that raise the temperature or at least cover them with adhesive tape, one may allow shehiya even of food that has not reached the level of ma’akhal ben Derusai.


Shevet Ha-Levi


Concerning the prohibition of hatmana (insulation), apparently Ashkenazim should have no problem.  The inner vessel with the food is surrounded on all sides by the heating shell, but it is not covered above (the vessel above has a lid, but there is no covering above the lid), and apparently it should be partial hatmana, allowed according to Ashkenazim.  This is the common ruling outside of Israel, and this is Rav Wosner’s inclination (Shevet Ha-Levi, Vol. IX, ch. 52-53):


As for the question of the slow cooker, concerning hatmana… my humble opinion is that one need not raise a fuss over those who allow this, since the simple meaning of the Rema’s words (253:1) indicates this: even if we are talking about coals, as long as there is an opening above without coals, this is not hatmana in a davar she-mosif hevel (calefactive insulation), but rather shehiya.  It is clear that this is true even if it is mostly covered except for above, as is explained in the Darkhei Moshe there, and this is what written by Shulchan Arukh Ha-Rav, ch. 253…


This is what the Magen Avraham writes, for one who reads it cleverly…


I have not forgotten Rabbeinu Tam’s Sefer Ha-yashar, where he indicates that he only allows this with very few coals, and this is what is written by the Chazon Ish…


But he also understands the leniency of the Rema as I wrote, and it is obvious that one who is lenient following the Rema, the Shulchan Arukh Ha-Rav and his group, and the Magen Avraham acts appropriately.  One who is stringent does not act without justification, but we have no power to annul it.  As for shehiya, there is the solution of covering the knobs and the like.


Rav Auerbach


On the other hand, Rav S.Z. Auerbach (Minchat Shelomo, Vol. II, 12:9) writes:


I have not permitted this, and on the contrary my view is the following: since the pot with the food is covered and insulated, all of it or most of it, by an electric heating vessel, the small airspace between them does not nullify the hatmana, since this is the way to cook also during the week.  In my view, it is considered actual hatmana with a davar she-mosif hevel, and one may not be lenient even about that which is fully cooked. 


According to him, since the pot is covered on all sides and the lack of a top cover does not hurt it — on the contrary, this is what we do on weekdays — this is considered hatmana, and it is forbidden.  This is how Rav Elyashiv rules (Orechot Shabbat, p. 540).[1]


A Solution


However, even according to the stringent view, there is a solution.  One may put some pebbles or pieces of ceramic tile and the like on the heating element and put the insert on top of them.  This will lead to the insert being raised a half-centimeter over the rim.  In light of this, the bottom and the lid are considered uncovered, as well as the small portion of the insert that protrudes.  These parts are already most of the pot, and, naturally, most of the pot is considered uncovered.  This is how Rav Elyashiv (loc. cit.) rules, taking the lenient view.[2]


We may add that according to the view of Rav S.Z. Auerbach as well, if the heating elements do not surround most of the pot, but are only below or only on the sides, the pot is not considered insulated.  It may be that using tape on the knobs is preferable, as one who wants to alter the temperature must remove the tape to do so.[3] 


Rav Ovadya


However, these allowances help only Ashkenazim, who are lenient about partial hatmana, while Sefardim, who are stringent about this apparently, there is no reason to allow putting food in a crock pot, even before Shabbat, since this is hatmana.[4]  However, Rav Ovadya writes (Chazon Ovadya, Shabbat, Vol. I, pp. 64-65) that one may be lenient about this when one makes food in this pot for eating in the morning, because one may enlist the view of the Rema, who is lenient about partial hatmana, with the views of those Rishonim who hold that there is no prohibition of hatmana before Shabbat for the need of the morning meal: the dish will be naturally ready, and there is no concern that one may stoke the coals for this purpose (Piskei Ha-Rid 47b, s.v. Tomenin; Shibbolei Ha-leket, ch. 57 in the name of Rabbeinu Simcha, cited by the Rema 257:1, as “Those who say”).  These explanations are not self-evident; however, since we are talking about a rabbinical doubt, whoever wants to be lenient has the right to do so.




In conclusion, there are those who allow putting food before Shabbat in a crock pot.  This is a widespread custom, and this is what Rav Wosner leans toward.  On the other hand, Rav Auerbach and Rav Elyashiv believe that one should not use this vessel because of the concern of the prohibition of hatmana.  For those who wish to take into account the stringent view as well, one may put pebbles below the insert (the punctilious attach adhesive tape to the knobs).  As for the Sefardim, the simple law is to be stringent and not to use this pot; however, Rav Ovadya is lenient about this, and one who follows this has upon whom to rely.


The dial may be set to a “slow” or “high” setting.  However, one should avoid the “automatic” setting if possible as there is a problem of removing the insert to serve the food, as there is a great chance that the electrical mechanism will immediately activate.  One who wants to use the “automatic” setting (this is generally more useful) may choose one of these two options:


1.     Not to remove the pot, but only its contents with a spoon.[5]

2.     To set up a Shabbat timer to turn off the device before mealtime (this will also save electricity).






Many people “hide” bags of food inside cholent or other dishes.  Apparently, there is a problem of hatmana in this, because the bag is insulated by the surrounding food.


Chazon Ish


However, the Chazon Ish argues that one may be lenient. 


The Gemara (40b) writes:


Rav Yitzchak bar Avdimi said: “I once followed Rabbi into the baths, and I wished to place a cruse of oil for him in the bath.  He then said to me, ‘Take water in a keli sheini (secondary vessel), and put the cruse in it.’”


Three things may be inferred from this: oil is subject to [the prohibition of] cooking; a keli sheini cannot cook; and making it lukewarm is [considered to be] cooking it.


In other words, one may take a cruse of oil and put it in a large vessel with hot water.  How can this be?  Even if there is no bishul (since we are talking about a keli sheini), there is still an issue of hatmana, because the small container is surrounded by the water in the larger vessel!


One may explain that Rav Yitzchak bar Avdimi did not put the cruse all the way into the water, but only partially.  For those who believe that partial hatmana is allowed, there is no prohibition in this; however, the Chazon Ish explains otherwise:


Here one is insulating the cold with hot water, but since there is no cover aside from the water, there is no problem of hatmana


Therefore, one is allowed to put a well-sealed container in hot water, as long as there is no issue of bishul, for example in a keli sheini


And there is no hatmana in this, and even if it reaches yad soledet bo (a scalding temperature), this is permitted, since the definition of hatmana is not met at all. 


We have learnt from all that has been said that when one heats food or soup, which has been fully cooked since Friday, for the children or for the delicate, one is allowed to put a container in hot water in a keli sheini even though it is yad soledet bo, and there is neither a problem of bishul nor a problem of hatmana. 


According to the view of the Chazon Ish, there is no prohibition of hatmana inside food.  The prohibition of hatmana involves coals or clothing and the like, but when one puts a container in food, this is not hatmana, and the Sages do not prohibit this (when they were concerned about stoking coals or boiling).[6]  In light of these words, the Chazon Ish allows heating a baby bottle in a vessel with hot water; similarly, one is also allowed to put a bag of rice inside cholent and the like, because hatmana is not forbidden inside food. 


Most Authorities


However, the words of the Mishna Berura (258:2) indicate that Acharonim do not accept the view of the Chazon Ish:


The Acharonim write that one is forbidden to take a vessel containing a cold drink and to stick it on Shabbat into a vessel with hot water so that it will warm up, even if it will not reach yad soledet bo, because this is truly the way of hatmana, since it is all submerged in it. 


Thus, hatmana would apply inside food, and this is view of most modern authorities: Rav Auerbach (Shemirat Shabbat Ke-hilkhata, Vol. II, ch. 42, note 242), Minchat Yitzchak (Vol. VIII, ch. 17) and Shevet Ha-Levi (Vol. III, ch. 47).[7]


Baby Bottle


In light of this, Rav Neuwirth (Shemirat Shabbat Ke-hilkhata 1:50) writes that one who wants to heat on Shabbat a bottle for a baby in hot water (in a keli sheini) must be careful to leave part of it exposed, in order to avoid hatmana.  This indeed is the proper custom, in order to accommodate the view of most authorities who disagree with the Chazon Ish.[8]  However, one who is lenient and covers the bottle with water has upon whom to rely, as according to the Chazon Ish there is no problem of hatmana in food, and we are speaking of a rabbinical doubt.[9]


Cooking Bag


However, even if there is a prohibition of hatmana in food, it may be that one may still put a bag of rice and the like in the cholent on Friday.  Rav Auerbach (loc. cit., Tikkunim U-milluim) claims that the prohibition of hatmana is based on the fact that the person is interested in heating the food via the substance enveloping it. 


When, for example, one heats a bottle of milk in hot water, he is interested in the water heating the milk in the bottle.  On the other hand, when one puts a bag of rice in cholent, the cholent and rice heat up together on the fire, and in terms of the heating, there is no benefit to the rice of being enveloped by the cholent.  One puts the bag of rice in the cholent for totally different reasons: in order to avoid using another pot or so that the cholent will impart some taste to the rice.  Alternatively, he puts the rice in a bag so that it will not break apart and become mixed with other food in the pot. 


Therefore, there is no problem of hatmana in using this method.  According to the Responsa Minchat Yitzchak (ad loc.) and Shevet Ha-Levi (ad loc.), one should make small holes in the bag, so that the cholent will impart taste to the rice, making them into one dish.  However, in the view of Rav S.Z. Auerbach, there is no need for this.  This is also what we find in Or Le-Tziyon (Vol. II, 17:13). 




Is one allowed to put hot water into a thermos on Shabbat?  It is understood that we are discussing only a non-electric thermos, and the question is whether there is a problem of hatmana.  At first glance, apparently one should forbid this, because the water is actually insulated in the container, and this is hatmana without adding heat (davar she-eino mosif hevel, which cannot be done on Shabbat itself).


Insulation with a Secondary Vessel


However, the Gemara (51a) cites the words of Rabban Shimon ben Gamliel:


Only the self-same kettle is forbidden;  but if one empties from one kettle into another, it is permitted: seeing that he is cooling it, will he indeed heat it up?!




In other words, if one transfers the water in the kettle from a keli rishon (primary vessel) to a keli sheini, there is no problem with insulating them afterwards, since in this transfer, the water cools, and therefore there is no concern that one may boil it.  Transferring the food to a keli sheini is an action of cooling, and since the person is moving in the direction of cooling, there is no concern that one will take then opposite action and come to boil the dish.  This, at least, is how Rashi (s.v. Lo aseru) explains:


There is no reason to decree lest one stoke, because now that he is cooling it intentionally, will he [come to] actively boil it?


The Rambam (4:5) explains the words of the Talmud thusly:


If one transfers hot food or water from its vessel into another vessel, it is permitted to insulate the second vessel with a davar she-eino mosif hevel on Shabbat, as one is permitted to cover cold food.  The prohibition against hatmana on Shabbat applies only to hot food in the vessel in which it was cooked.  If it has been transferred, this is permitted.


The Rambam indicates that the allowance is based on the very fact that the food is located in a keli sheini and is considered, in some ways, cold.  As opposed to Rashi, who believes that the person’s aim is determinative, the Rambam follows the state of the dish, and he determines that the prohibition of hatmana exists only for food located in a keli rishon, not food transferred to a keli sheini.




Hatmana in a thermos seems to be dependent on the dispute of Rashi and the Rambam.  According to Rashi, this will be forbidden, as the aim of the person is to maintain heat, not for the contents to cool down.  According to the Rambam, one should allow this, since the liquid has passed to the keli sheini.[10]


Chazon Ish


The Chazon Ish (37:32) allows putting hot water in a thermos, not only based on the Rambam’s view, but also on an additional innovation:


The Ran follows the view of the Rambam, and this is what the Mishna Berura 257:29 writes as the practical halakha.  It appears, according to this, that it is permitted to pour water from an urn to a thermos on Shabbat, because even if we consider the thermos to be hatmana with cloths, there is still the allowance of a keli sheini.

It is possible that using a vessel woven with a cloth around it is not considered hatmana, for they only decreed against insulating the vessel with a cloth, but putting inside a vessel is not included in hatmana, because every vessel protects what is in it, so that it does not cool quickly, and they did not forbid putting it in the vessel on Shabbat.  According to this, even following the explanation of Rashi, it would be allowed. 


According to him, it may be that there is no issue of hatmana unless one puts a vessel inside clothing, but putting food into a vessel is not hatmana.  The proof is that every vessel maintains the heat of the food in it, and in any case they did not forbid putting hot food into a sealed vessel on Shabbat.


Another Justification


Rav Moshe Feinstein also allows this (Iggerot Moshe, Vol. I, ch. 95), while noting another reason to be lenient about it even according to Rashi’s view:


However, when putting into a thermos, in my humble view, it appears that there is another reason to allow, because putting food into a thermos is no better than putting it into any another vessel until one seals its mouth with a cover designed for this.  Now, in this there is no prohibition, because one is allowed to cover the pot even on Shabbat, since this is the way to protect it from an number of things, that it will not spill and that debris and flies will not get into it, et cetera, so that even if it maintains its heat, one may use it. 


According to this reason, one may also leave a hot-water bottle under one’s blanket, because the essential aim of the person is not to maintain the bottle’s heat but to heat the bed. 





Practically, the Shevet Ha-Levi (Vol. I, ch. 93) is stringent not to put water in a thermos, but the halakhic consensus is to allow this: this is what we find to be the ruling of the Chelkat Yaakov (OC, ch. 84), the Tzitz Eliezer (Vol. XI, ch. 29) and Shemirat Shabbat Ke-hilkhata (1:70-71).  This appears to be the essential halakha.


To summarize, one may put hot water in a thermos on Shabbat, and there is no problem of hatmana, for a number of reasons:


1.     There is no hatmana in a keli sheini (Rambam).

2.     There is no hatmana of food in a vessel (Chazon Ish). 

3.     Closing the cap, which completes the insulation, is designed to protect the contents from dirt, not to maintain their heat (Rav Feinstein).






Translated by Rav Yoseif Bloch 

[1]      See Moriya 5755, 233-235 and Orechot Shabbat, p. 529 ff.

[2]      However, in the view of Rav S.Z. Auerbach, this is insufficient: the bottom of the pot does not count as an uncovered part, since it is not exposed to air (Orechot Shabbat, ch. 2, note 149).  However, Rav Auerbach concedes that one may be lenient when the heating elements are only below or only at the sides, as is true of many of these devices.  Similarly, we may add the element of covering the knobs; see below.

[3]      We can also enlist the view that there is no hatmana in a clay-daubed oven; see our first shiur on hatmana.

[4]      Also, covering or sealing the knobs should be effective only according to the Rema, and not according to the Shulchan Arukh  (254:1); see our original shiur on hatmana.

[5] This is based on the Chazon Ish, who is lenient about removing with a spoon even when the pot is on the fire when there is no other way (as understood, on the condition that the food is fully cooked); see our previous shiur on this topic.

[6]      We have found in the Gemara (145b) that one is allowed to put “Rabbi Abba’s chicken” even in a keli rishon (off the fire), and this indicates that hatmana in food is not a problem.  The Chazon Ish is unwilling to assume that the leniency here is due to the hatmana being incomplete in each of these cases, since the halakhic ruling follows the Shulchan Arukh and partial hatmana is forbidden (37:19).

[7]      The words of the Ran (18a, Rif, s.v. Garsinan) also seem to undermine the view of the Chazon Ish. The Ran writes that in pouring water into a dish, there is no problem of hatmana, since the water mixes with the dish.  This would seem to indicate that essentially there is a problem of hatmana in food, and only when the insulated substance mixes with the food may one allow it. In any case, the words of the Ran indicate that even according to the view that disputes the Chazon Ish, prohibiting the keli sheini of a container of food with other food, there is no prohibition of insulating a food with no container inside other food, for example putting chicken in cholent or meat in soup (when it is not on the fire); in these cases, the foods mix and become one dish.  This is the ruling of Rav Neuwirth (Shemirat Shabbat Ke-hilkhatah 1:72).

[8]      This solution should only work for Ashkenazim, who are lenient about partial hatmana; it should not help for Sefardim, who are stringent about this.  However, Rav Ovadya Yosef writes (Chazon Ovadya, Shabbat, Vol. I, p. 66) that even Sefardim are allowed to submerge a bottle of cold milk in a keli sheini, because one is allowed to do hatmana by putting something cold in a davar she-eino mosif hevel (257:6, following the mishna, 51a), and a keli sheini is considered a davar she-eino mosif hevel. The Mishna Berura and his group are stringent about this, maintaining that a keli sheini is a davar she-mosif hevel, since at least at this time, it is heating the cold bottle.  However a number of Acharonim are lenient about this and believe that since the vessel is cooling off, one should not consider it mosif hevel (Eliya Rabba 258:3; Shulchan Arukh Ha-Rav 318:23).  Following the view of Rav Ovadya it is possible to be lenient about this view, and particularly one may enlist the view of the Chazon Ish. This is the lenient ruling of the Tefilla Le-Moshe as well (Vol. I, ch. 34). 

[9]      Similarly, since we are talking about a keli sheini (because one cannot heat a cold liquid in a keli rishon due to the prohibition of cooking), one may enlist the Acharonim cited in the previous note who believe that one may do hatmana of a cold item in a keli sheini.

[10] However, according to the Rambam, we need to ask the following question: does the transition to a keli sheini make hatmana permissible?  If so, one should allow this even in a thermos.  Alternatively, it may be that hatmana in a keli sheini is allowed because this is not frequently done, and if so, one should forbid doing this with a thermos, because this is a vessel designed for hatmana.