- Question: [Thursday, 8th Shevat 5781]
Is it permitted to heat up a Kugel on Shabbos and if so may I do so with the tinfoil on top of it or is this considered insulation?
You may heat up a Kugel on Shabbos on top of another pot so long as the Kugel and its tin is dry to the touch and the Kugel is not too oily to the point that its oil will visibly melt and ooze out of the Kugel as a result of the heat. It is best not to use any tinfoil when heating it up in order to avoid any question of the insulation or cooking prohibition which applies in certain cases when tinfoil is used. See the explanation below for the details of the cases in which it would be allowed to use tinfoil.
It is permitted to heat up a Kugel on Shabbos only if one follows the above regulations in order not to transgress neither the cooking, or looking like your cooking, or insulation, prohibition. The way this is done is as follows:
Negating a cooking prohibition: First off one must verify that it does not involve the cooking prohibition by making sure that it is fully cooked, which is usually the case, and that it is dry enough from oil or liquid to the point that if you were to touch it, it would be unable to make another finger feel wet. Likewise, it may not contain congealed fat or oil which will visibly ooze out of the Kugel when heated up. [Mere moisture that is visible when you cut the Kugel is irrelevant to this issue.] To note, that accordingly one must also make sure that the bottom and sides of the tin that is holding the Kugel is also dry.
Negating a “looking like you are cooking” prohibition: Second one will need to heat it in a way that it does not transgress the looking like your cooking prohibition, and thus it may only be heated on top of another pot that is already on the fire, such as on top of the Chulent pot, or on top of the water urn. Alternatively, one can place an upside-down pot on top of the electric plate or Blech and then place the Kugel on top of it.
Negating an insulation prohibition: Third to negate the insulation prohibition, it is prohibited for one to place a towel or other covering over the Kugel for the sake of conserving its heat, even if one only places it over the very top, and certainly if one wraps the sides of it with the insulation material.
The issue with tinfoil: Now regarding the specific question of covering it with tinfoil: If the purpose of placing the tinfoil over the Kugel is for the sake of insulating the heat then this would be forbidden due to the insulation prohibition even if it is only placed on the very top of the Kugel, as stated above. If, however, the tinfoil is there simply to act as a cover for the Kugel, similar to the cover of a pot which is also there to prevent things from falling inside, then this would be permitted to be done. Furthermore, if the tinfoil only covers the very top of the tin of the Kugel, and not the majority of its walls, and it does not touch the actual Kugel but rather hovers over it from on top, then this would likewise be permitted even if ones intent is for insulation purposes. If, however, the tinfoil clings to the Kugel and its purpose is for insulation then it would be forbidden to place it over the fire. When using the tinfoil that the Kugel was wrapped in when put inside the fridge, one must always be careful that there is no condensation under the tinfoil in order so one does not transgress the cooking prohibition. It goes without saying that it is forbidden to cut a new piece of tinfoil on Shabbos to cover the Kugel with. Bottom line, the best thing is to always remove the tinfoil when heating it up in order to avoid the above issues.
Sources: Regarding the cooking prohibition by moisture and liquids see: Admur 253:19; 318:11; 318:17; 25; 31; Admur in Siddur; Michaber 318:4; Levush 318:16; Taz 318:20; Chasam Sofer 74; Divrei Nechemia p. 36 in Hosafos; Ketzos Hashulchan 124 footnote 37; Igros Moshe 4:74:7; Or Letziyon 2:30:13; Shabbos Kehalacha Vol. 1 p. 24 and p. 142; See Shabbos Kehalacha p. 148-151 Regarding the looking like your cooking prohibition see: Admur 253:14 [prohibition to place directly on fire]; Admur 253:26; Michaber 253:3; Igros Moshe 1:93; 4:74-32; Shabbos Kehalacha Vol. 1 pages 416-418; Piskeiy Teshuvos 253:28-29 and footnote 264; SSH”K 1; [allowance to place over pot although prohibition to place directly over electric plate or blech; Zera Emes, Mahram Brisk 2:76, Maharam Shick 117, however permits to place directly on Blech]; Regarding the insulation prohibition see: Admur 257:1-2; Admur 257:10; Mahadurah Basra 259; Michaber 257:8; Ketzos Hashulchan 71 footnote 34; Shabbos Kehalacha Vol. 2 page 56-58; Chazon Ish 37:19 Regarding if wrapping in tinfoil is defined as insulation see: Mahdurah Basra 259; Igros Moshe 4:74 Hatmana 3; Rav Shlomo Zalman Aurbach brought in Shabbos Kehalacha ibid; Pnei Shabbos 12; Maor Hashabbos 1:9; Koveitz Mibeis Levi 6:36; Shabbos Kehalacha Vol. 2 page 41; Piskeiy Teshuvos 258:4