Shiur #21: Hatmana (Insulation)

  • Rav Yosef Zvi Rimon



By Rav Yosef Zvi Rimon


Shiur 21 – Hatmana (Insulation)



May one cover pots on the plata with blankets?  Is it permissible to do this on Shabbat itself?


May one use a “plata cover?”


The Double Prohibition of Hatmana


This prohibition has many details, and we will suffice here with the principles and practical matters.  There are two types of hatmana, based on the substance used, which may be mosif hevel (calefactive, adding heat) or eino mosif hevel (non-calefactive, not adding — but merely maintaining — heat).  The former includes peat, compost and salt (mishna, 47b). 


The Gemara (34a) indicates that in the context of the prohibition of hatmana the Sages forbid two things:


A)    Even a davar she-eino mosif hevel may not be used on Shabbat itself.

B)    Even on Friday, a davar she-mosif hevel may not be employed to insulate food for Shabbat.


In the Gemara, it is explained that the two prohibitions have different reasons.  The Rishonim argue, following different texts, which reason applies to which prohibition.  We will explain the view of Rashi.  This is what the Gemara says according to his version: 


Rava said: “Why was it said that one must not do hatmana after nightfall even with a davar she-eino mosif hevel?  For fear lest he make it boil.”

Rava also said: “Why was it said that one must not do hatmana with a davar she-mosif hevel, even by day?  For fear lest he put it away in hot ashes containing a burning coal.”

Abbayei said to him, “Then let him put it away!  We fear lest he rake the coals.”


If so, using a davar she-eino mosif hevel is forbidden because one may boil.  When one covers the pot with a davar she-eino mosif hevel, he first ascertains that the pot is sufficiently hot, so that it will remain warm until the meal uses the cover.  Therefore, when one is setting up the hatmana for a pot, there is a great concern that one may boil it, so that it will actually be hot at the time of hatmana.  This concern exists specifically at this time, and therefore the problem exists only on Shabbat.  Before Shabbat, there is no problem of using a davar she-eino mosif hevel, because there is no problem if one actually wants to boil it beforehand.[1]


However, when it comes to a davar she-mosif hevel, the concern is that one may use ashes; if we allow one to use these substances, he might even use hot ashes that still have smoldering coals in them.  If one comes to do this, there is a concern that one may rake these coals in order to “turn up” the heat, violating the biblical prohibition of kindling.  This concern exists even when one does this before Shabbat, because in this case there is a concern that over the course of Shabbat one may rake the coals in order to increase the heat of the pot.  Therefore, the Sages forbid using a davar she-mosif hevel, even if one does so before Shabbat begins. 


Covering with Cloths 


Even in modern times, we often use a davar she-eino mosif hevel, such as towels or blankets.  On the other hand, we do not use a davar she-mosif hevel.  Is the law still relevant?


Argument of the Rishonim


This is dependent on an argument among the Rishonim, who discuss mixed hatmana before the commencement of Shabbat: may one leave a pot on the fire and cover it with a davar she-eino mosif hevel, such as blankets?  The Ran (47b) cites an argument about this:


There is a dispute about this, for some say… that since the pot does not touch peat, this is shehiya (retention), not hatmana  Even though one has put a davar she-eino mosif hevel on top, it is still allowed, because hatmana is allowed when using a davar she-eino mosif hevel; thus the shihuy below is independent, and the hatmana above is independent, and each is allowed…


Our current custom follows this view: one may do hatmana with clothing or another davar she-eino mosif hevel, and the stewpot may sit on the sprinkled stove, which is mosif hevel, but this is permitted, because the shehiya is independent, as is the hatmana  This is the view of the Ramban, z”l.


On the other hand, Rabbeinu Yona, z”l, writes… that when we allow shehiya on top of the sprinkled stove, even though it adds heat, this is only if there is no hatmana above…  However, if there is hatmana, one demonstrates that he is preoccupied with its heat, and he needs it for the next day, and because of this, one may not leave it atop a sprinkled stove or anything that is mosif hevel, lest one come to stoke… 


This is the view of the Rashba, z”l, as well. 


Thus, the Ramban sees this as the juxtaposition of permitted shehiya and permitted hatmana, while the Rashba and Rabbeinu Yona argue that there is no such thing: while the Sages do allow shehiya under certain conditions and do allow hatmana under certain conditions, they would not permit doing both simultaneously, as in this case, the latter undermines the former: one demonstrates that the heat of the food is of paramount importance by doing hatmana above, so that the concern about stoking the coals is still problematic.


Shulchan Arukh


The Shulchan Arukh (257:8) adopts the view of Rabbeinu Yona and the Rashba:


Even though one may leave a pot on a coal-fueled stove according to the conditions we mentioned in Chapter 253, if it is covered with clothing — despite the fact that the clothing does not in itself add heat — the fire beneath it adds heat (and the pot may not be left there). 


The Shulchan Arukh explains the reasoning in a slightly different way than Rabbeinu Yona and the Rashba do.  In his view, it is true that initially the clothing does not add heat, but since it is on something hot, it becomes hot and becomes mosif hevel. 


On a Plata


In light of this, one may not put a towel over a pot on the plata, even before Shabbat, because this is considered hatmana in a davar she-mosif hevel.  In fact, it is forbidden to cover the pot even if it is atop another, because ultimately the cover heats up (via the plata or the lower pot), and it is considered to be mosif hevel.





Touching the Coals


Is there any permissible way to cover the pots on the plata?  In order to clarify this, we should examine what is defined as hatmana.  What about partial covering?  This seems to be a matter of dispute.  Rabbeinu Chananel (37a) indicates that not only is partial hatmana considered hatmana, but even if only the bottom of the vessel touches the heat source, it is still considered hatmana:


This shehiya is not hatmana unless it is like a metal seat for the pot while it sits on stones and the like, but hatmana over coals is forbidden according to everyone, for we have established that hatmana that adds heat is forbidden even while it is still day.


In his view, even if the pot sits on coals, this is hatmana, and only if it is suspended in the air can we look at it as shehiya.


Rabbeinu Tam (Sefer Ha-yashar, ch. 235) believes otherwise:


The way that we do hatmana for our hot food — even though there are some cinders that are as tall as a finger — is not prohibited, because hatmana means that most or all of it is covered.


In his view, it is not hatmana unless most or all of the pot is covered.




The Shulchan Arukh (253:1) rules in accordance with Rabbeinu Chananel, quoting him virtually verbatim, but the Rema is lenient:


There are those who say, that even if the pot is actually standing on the fire, as long as it is uncovered above, this is not called insulation, and it is allowed.  This is the custom.


From this we may conclude that Sefardim are not allowed to cover the pot on the plata even partially, and apparently according to them it is forbidden to put a pot on top of a plata before Shabbat even if it is not covered at all, because it is “covered” on its bottom by the hot plata. 


On the other hand, according to the Ashkenazim, one is allowed to put a pot on the plata and even cover it with a blanket, if it does not cover all of it.


We will try to clarify part of this law, for Sefardim and for Ashkenazim.


Hatmana for Ashkenazim 


As we have seen, Ashkenazim allow partial hatmana.  What exactly is the definition of this?


The Chayei Adam (2:5) writes that only when one insulates above and below and from all sides is it considered hatmana.  However, in another place (20:22), he contradicts himself and writes that partial hatmana is only when less than half of the surface of the pot is covered.


Similarly, the Mishna Berura (253:69) writes that if one insulates with pillows and leaves an opening above — this is not hatmana, while in another place (257:43) he writes that only if it is half-uncovered is this true.[2]





For Ashkenazim, Rav Feinstein (4) rules that only if the pot is covered above and on the sides it is considered hatmana, and this is the ruling of Rav Neuwirth (Shemirat Shabbat Ke-hilkhata 1:66).[3]  According to this, hatmana requires that everything be covered.  Indeed, one should leave a significant portion, rather than a symbolic portion, uncovered.


For Sefardim, based on what we see in the Shulchan Arukh, every time one puts a dish on a heat source, this violates partial hatmana, even if the dish is not covered at all.  Rav Mordekhai Eliyahu rules in accordance with this ruling, and he designed a special plata, in which the standard metal encasing the element is covered by another plate of metal (with air in between). 


Rav Ovadya Yosef (Yabbia Omer, Vol. VI, OC, 32:5) is lenient for a number of reasons.  The central reason is that the pot does not stand directly on the heating element; there is air dividing the heating element from the metal of the plata, and even the metal itself divides between the heating element and the pot, so this is not considered partial hatmana.[4]


Another Consideration


There is another reason to be lenient about this, in light of the words of Tosafot (48a, s.v. De-zeitim):


This is puzzling: how can we insulate upon our stoves… even though we may sweep it, it adds heat just like olive peat!  The Ri says that we may give a reason to justify this custom, for concerning peat there is a concern that he will totally bury the dish in it, but in stoves, this is not applicable.


According to Tosafot, partial hatmana is only a concern if it is physically possible to totally surround the pot with the heat source, such as peat or coals, but there is no such concern with a hot stove, since one cannot bury a pot in it.  According to this, even those who are stringent about partial hatmana are allowed to set up a pot on Friday on a plata or blech, since one cannot use them for hatmana.[5]  This is what is written by the Tefilla Le-Moshe (Vol. I, 1:15-17).


Nevertheless, once the pot is set on the plata, Sefardim have no allowance to cover it with blankets, because it is physically possible to entirely insulate the pot with blankets, creating a davar she-mosif hevel, as we saw above.


Not Touching the Walls


Is there any way for Sefardim to cover the pots on the plata?


Tosafot (ad loc.) offer a suggestion:


Some dig a large hole, making a building of bricks around from every side and below; they heat it well and sweep it, and then they insulate the pot in it.


Why is this not hatmana, considering that the pot is totally surrounded by the fire-pit’s walls?


This is not comparable to hatmana with a davar she-mosif hevel, because it is only forbidden when one packs around it something akin to hot ashes, but concerning an oven or hole that has air between walls and the pot, one need not forbid more than shehiya, even though the entire pot is in the oven. 


Thus, according to Tosafot, the air space between the pot and the walls removes it from the category of hatmana.  Based on this, one may conclude that leaving the pot in the oven is not considered hatmana (indeed, there are other problems in this act of shehiya, as we have seen previously).  This is true even if the pot touches one of the walls of the oven, because for the other walls there is an air space (Bei’ur Halakha 257:8, s.v. Sharei). 


A Wide Cover


According to the same principle, one may cover with clothes a pot that sits on the fire or on the plata, if we are concerned that there will be air between the clothing and the walls of the pot.  This is how the Shulchan Arukh (257:8) rules:


However, as long as the clothing does not touch the pot, even though there is a fire below it, since one does not do it in the way of hatmana, it is permissible… 


If one puts on the pot a wide utensil that does not touch the walls of the pot, and one puts clothing on the wide utensil, this is permissible; since the clothing is only put on the wide vessel and does not touch the walls of the pot, there is no [violation of] hatmana.


Creating the airspace is thus effective according to Sefardim as well.  It may be that according to this, one may use a blanket to directly cover a number of pots, so that the cover is not tightly packed around each individual pot (and there is always some space between the pots, at least in relation to most of the pot), but it is worth it in any case to leave one side open, since one possibly may relate to all of the pots as one form of hatmana.

Rav Ovadya


According to Rav Ovadya Yosef (Yabbia Omer, Vol. VI, OC, ch. 33), when we are talking about pots sitting on a plata, one may be lenient and cover them before Shabbat in a full way, even without the airspace.  In his view, since the prohibition of hatmana before Shabbat is based on the concern of stoking when we are talking about a plata: it is impossible to stoke or turn up the heat — the prohibition is not appropriate at all.[6]  This ruling is not based on Sefardic custom, but upon the principles of the Rishonim and the halakhic authorities, and therefore even the Ashkenazim who want to be lenient in this way may do so. 



On Shabbat


However, on Shabbat itself, there is no allowance to cover the pot in a way that is tight and complete even if it is standing on a plata, since the prohibition of hatmana on Shabbat is based on the concern that one may cause a pot to boil before hatmana, and the concern exists when the hatmana is on the plata as well, even if the hatmana is with a davar she-eino mosif hevel — for example, one covers a pot sitting on the countertop with a blanket.  Therefore, one may cover a pot on Shabbat itself only in a partial way (Ashkenazim) or in a way that allows for airspace between the pot and the cover. 




Practically, when it comes to putting it on the plata before Shabbat, among Sefardim, there are those who are stringent not to put foods directly on the plata but only on top of an empty vessel; however, many are lenient about putting it on the plata without any suspicion of hatmana.  According to the Ashkenazim, placing on the plata is not considered hatmana, and therefore it is certainly allowed before Shabbat. 


As for covering the pot with blankets and the like, before Shabbat one may cover the pot, but according to the Sefardim it is worth being stringent to ensure that there will be air between it and the cover, and according to the Ashkenazim, one may cover it tightly, as long as one leaves part of the pot uncovered. 


However, when the pot is put on the plata, one who is lenient and covers it tightly and fully has upon whom to rely.  On Shabbat itself, one may not cover the pot tightly and fully, but one must maintain the airspace between the cover and the pot or (according to Ashkenazim) leave a small and significant part of it that is not covered.

Translated by Rav Yoseif Bloch


[1] The Yerushalmi (4:1) notes additional answers for the prohibition of hatmana on Shabbat even for a davar she-eino mosif hevel: a) instead of coming to the study hall on Friday night, they will be busy with hatmana; b) others may suspect that one has not sufficiently prepared for Shabbat (Penei Moshe) or that one cooks on it (Korban Ha-eda).  These reasons are not mentioned by halakhic authorities.

[2]      It may be that when it comes to davar she-eino mosif hevel, only fully covering it is forbidden, while for a davar she-mosif hevel, even covering most of it is forbidden.

[3]      However, it is not clear how we have reached this decision, because Rabbeinu Tam is stringent about this, and there are also a number of contradictions in Mishna Berura and Chayei Adam, but in any case, since the great authorities have decided leniently, and since this has echoes among the Rishonim and this is the question of a rabbinical law, it appears that one may rule accordingly.

[4]      According to this view, one may be lenient, not only with a plata, but even with a blech. Below we will see that according to the view of Rav Ovadya, one may be even more lenient: hatmana does not apply at all (even if one uses blankets), since its heat cannot be increased.

[5] According to this approach, Sefardim would be allowed to leave pots even on an open flame, because it is not possible to insulate it, while according to the view of Rav Ovadya Yosef, this is forbidden because of hatmana.

[6]      Hatmana in an oven sealed with clay depends on a dispute among Acharonim.  The Mishna Berura (257:47) cites a dispute about whether one can cover a pot with coals when it is found in an oven sealed with clay.  The Eliya Rabba and others allow it, because there is no concern that the person will stoke the coals, while the Maharshal and others forbid this.  According to the Maharshal, the prohibition of hatmana is not based on the concern that one may rake the coals on this Shabbat.  The prohibition relates also to a davar she-eino mosif hevel that cannot be stoked, as it were, such as peat and fertilizer, and it emanates from the concern that the person will come on another Shabbat to insulate with hot ashes, and then one will stoke the coals, and therefore one may forbid hatmana also in an oven daubed with clay, even though right now one cannot stoke the coals.  It makes sense that according to Eliya Rabba and his colleagues, specifically with peat and the like, there is a concern of hatmana lest a person insulate with hot ashes and not pay attention to the distinction, while an oven daubed with clay has a clear roadblock that prevents stoking the coals, and no one will think that hatmana is permissible without this roadblock. 

In fact, the Mishna Berura concludes that it is good to be stringent ab initio, but in Shaar Ha-tziyun (46), he writes that in the words of the Or Zarua (Vol. II, ch. 8), it appears that he is lenient about this. If the Maharshal would have seen this, it makes sense that he would not be as stringent.  Rav Ovadya (loc. cit.) follows the Or Zarua, that even on a plata there is no issue of hatmana, since a person has no access to the heating element, and it is similar to an oven daubed with clay.  (However, the Chazon Ish, 37:20, explains the Or Zarua’s view in another way, and he concludes that one should be stringent about an oven daubed with clay; this is the view of most Acharonim concerning the plata.)