Last week, we discussed some general laws of insulation on Shabbat. In previous generations, people would insulate a pot of food for Shabbat in sand or clothing in order to retain its heat for Shabbat morning, as they did not have urns or electric hotplates. Insulation was therefore crucial for them.
Two Different Types of Insulation
We have explained that there are two categories of insulation: Insulating in a material which adds heat, such as sesame seeds or olive sediment, which get hotter as a result of their unique molecular composition and thus increase the heat of the pot of food being insulated within them. Insulation in such materials is absolutely forbidden, even if the insulation is being done before the onset of Shabbat, as a result of a rabbinic injunction lest one come to desecrate Shabbat, as we have explained before.
On the other hand, there are other insulation materials which do not add heat and merely retain the pots current heat, such as feathers, clothing, etc. If one wishes to use such materials to insulate one’s pot of food for Shabbat this will be permissible as long as this is done before the onset of Shabbat. However, any type of insulation is forbidden on Shabbat itself.
Elisha of the Wings
The Mishnah (Shabbat 49a) states that it is permissible to insulate using “a dove’s wings,” i.e. dove feathers, since feathers do not add heat. The Gemara there states that Rabbi Yannai said that one who dons Tefillin must make sure one’s body is clean like Elisha of the Wings. The Gemara inquires why he was called that to which the Gemara explains that there was a period when the Romans decreed that any Jew who donned Tefillin would have his brain plucked out. Elisha, nevertheless, donned Tefillin and wore them in the marketplace because he thought that the Caesar’s officers would not see him. Suddenly, an officer spotted him; Elisha began to run and the officer gave chase. As the officer caught up with Elisha, Elisha grabbed the Tefillin on his head and covered it in the palms of his hands. The officer asked, “What is in your hands?” Elisha replied, “Dove’s wings.” “Open your hands!” the officer commanded. Elisha opened his hands and a miracle occurred and he was actually holding a dove’s wings. It is for this reason he was called “Elisha of the Wings.” Why did Elisha tell the officer specifically that he was holding dove’s wings? This is because of the verse in Tehillim, “Wings if doves hidden in silver,” which is a reference to the fact that just as a dove’s wings protect it, so too, the Jewish nation is protected by the Mitzvot.
Insulation Using a Towel and Returning It
We have explained that since a towel is considered a heat retainer and not something which adds heat, among other reasons, many people customarily cover the Chulent pot on the electric hotplate with a towel before the onset of Shabbat. Those who customarily do so indeed have on whom to rely. If the pot was covered with a towel before the onset of Shabbat and then sometime during the course of Shabbat the towel falls off, one may place the towel back on the pot to cover it again. Nevertheless, the above is only permissible if the Chulent (or other contents of the pot) is already fully-cooked, for if not, covering the pot with the towel again will actually be making the food cook quicker and this constitutes the prohibition of cooking on Shabbat.
This law applies irrelevant of the issue of insulation. For instance, if one left a pot of food on the electric hotplate before Shabbat and the food is not yet fully-cooked and during the course of Shabbat one removes the lid of the pot to check on the status of the food, if one sees that the food is not yet fully-cooked, one may not place the lid back on the pot, for doing so would constitute expediting the cooking time of the food and this is absolutely forbidden. Thus, many people commonly make sure the Chulent is cooked very well before the onset of Shabbat in order to avoid such issues. If this is not possible for whatever reason, they take care not to touch the Chulent pot at all until Shabbat morning so as not to transgress the prohibition of cooking on Shabbat.
Extra care should be taken that when one covers a pot of food on the electric hotplate with a towel that the towel does not touch the hotplate as this is clearly a fire hazard.