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Hatmana (Insulating) Food Going into Shabbos 2 – Why Did Chazal Prohibit; Defining Insulation – (Klal 2 Siman 5) Erev Shabbos- S0048

D'var Halacha
D'var Halacha
Hatmana (Insulating) Food Going into Shabbos 2 - Why Did Chazal Prohibit; Defining Insulation - (Klal 2 Siman 5) Erev Shabbos- S0048

 We are continuing in siman 5, discussing the halachos of hatmana. The Chayei Adam writes that Chazal prohibited insulating a food item even before Shabbos with an item which is mosif hevel, generates heat. On Shabbos itself, it is assur to perform hatmana even with an item which is maamid hevel, maintains the heat. 

 The Gemara gives two reasons as to why Chazal prohibit hatmana. One is a concern that as the person comes to insulate his food, he will notice that it is not as hot as he wishes, and will want to heat up their pot (and food) before insulating it, so they may stir the coals to improve the heating fire. If so, there is a double concern of bishul and mavir. This first concern only applies to Shabbos itself.  

The second reason is a concern that if one will insulate their food with a davar mosif hevel, they may think they can insulate with hot ash also. If one uses hot ash, they may come to stir the ash and coals on shabbos. Therefore, already before Shabbos one may use the wrong material, and then make a mistake on Shabbos. This concern only applies to a davar mosif hevel. it is muttar to insulate with a davar maamid hevel before Shabbos, as one will not confuse that with hot ash.  

The Chayei Adam continues, and writes that it is muttar to perform hatmana with one’s oven. He explains that the definition of hatmana is when the insulating material touches the pot which is being insulated. Thus, for example, if one places a board on top of their pot and drapes a down comforter over the board such that the blanket is not touching the sides of the pot, it is muttar. An oven functions in a similar manner, so there is no issue of hatmana.

It is important to note that although the pot itself touches the food, there is no issue of hatmana between the pot and the food, because one is not trying to insulate the food through the pot, rather to store and contain it in the pot.

The Chayei Adam gives an example. Although the specific example is not so relevant, there is an important point developed within the example, which we will discuss in the next shiur. 

 We walk away with the important points 

  1. that there is no issur of hatmana that the pot is touching the food since one is not trying to insulate the food in the pot, 
  2. and that hatmana only applies when the pot is insulated directly.

The Chayei Adam does not discuss whether the issur of hatmana applies when one insulates something not for the purpose of maintaining the heat, but for another purpose, such as keeping it clean. For example, if one wishes to insulate their potato kugel by wrapping it up and placing it into their cholent, but wishes that it remain intact so they can eat it separately. In this case, Chazal did not extend their issur and it is muttar. 


  • A davar mosif hevel cannot be used for hatmana even before Shabbos
  • A davar maamid hevel can be used for hatmana before Shabbos, but not on Shabbos itself.
  • Hatmana is defined as when the insulating item directly touches the pot. Otherwise, there is not issur of hatmana.
  • If one wishes to insulate food not for the purposes of keeping it warm, but for other purposes, they may do so.


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