Conserving the heat of a pot which contains undercooked food:

A. Placing a pot of uncooked food on top of a hot pot that is on the fire, or near a heat source [Blech, electric plate, open flame]:

Foods that are not fully cooked may not be placed near a fire or near another heat source [i.e. blech, electric plate], if the food can reach Yad Soledes in that area, as explained in Halacha 3A. Likewise, even if the uncooked food is already Yad Soledes, it is forbidden to place it near these heat sources even simply to conserve the heat.[1]

B. Placing a pot of uncooked food on top of a hot pot that is off the fire:^[2]

It is permitted to place a hot Yad Soledes pot of uncooked food on top of a hot pot that is off the fire, even if this lower pot is Yad Soledes, in order to conserve its heat.[3] If, however, the pot of uncooked food is not hot to the point of Yad Soledes, then it is forbidden to place it on top of a hot pot if it can heat it to Yad Soledes, even if it is off the fire, as explained in Halacha 3B.

C. Sealing the cover of a pot of uncooked food on Shabbos:^[4]

It is permitted to seal the lid of a pot in order to retain its heat. This applies even if the food is not fully cooked, so long as it is off the fire.

D. Insulation-Placing towels and blankets on top of or sides of hot pot of un-fully cooked foods:[5]

• Example- May one re-insulate a pot or add insulation to a pot that was insulated before Shabbos even if the food is not fully cooked?

Insulating even fully cooked foods on Shabbos carries with it certain restrictions, and may only be done in specific circumstances, such as if it was already insulated from before Shabbos, as explained in length in Chapter 4. Now, even in those cases that insulating the food on Shabbos is permitted, as explained there, if the pot is standing over a source of heat, then one may only add insulation material to it if the food is fully cooked. If the food is not fully cooked, then it is forbidden to add any material even to the insulated cover of the pot. [However, if the pot is not on any source of heat, then one may reinsulate it, or add more insulation to it on Shabbos, even if the food is not fully cooked, so long as it was insulated before Shabbos.^[6]]

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[1] Implication of Admur 318:14 brought in next Halacha that the allowance is only to place it on top of a pot that is off the fire; Admur 254:4 as learns Tehila Ledavid 254:4, that Admur prohibits placing uncooked food on top of a pot that is on the fire even the uncooked food is Yad Soledes

[2] Admur 318:14 “A vessel which contains a hot food which is Yad Soledes is permitted to be placed on top of a pot which is insulated in clothes in order, so it retain its heat and not get cold. This applies even if [the food in the upper pot] is not yet completely cooked in which case doing something to hasten its [further] cooking contains the cooking prohibition, nevertheless [here it is allowed to place it on top of another insulated pot which is not on a source of heat] being that it is impossible for it to become completely cooked through doing so and it cannot even further cook it, and it rather only retains its heat.”; [See also Admur 257:8 that allows adding insulation so long as the pot is not on top of a constant heat source. However, see 254:4 which rules it is forbidden to place uncooked foods on top of an insulated pot; Tehila Ledavid 254:4 establishes the case there [in 254:4] to be referring to a pot that is on the fire and is insulated in a permitted way, such as with a board over the top of the pot, and the insulation is thus not touching the walls of the pot.]; Michaber 318:6 [however does not mention uncooked food]; Taz 318:9; Elya Raba, brought in M”B 318:50

Other opinions: Many Poskim rule it is forbidden to place hot uncooked food on top of a hot pot due to the cooking prohibition. [Mahraiy Ben Chaviv; Bach; Olas Shabbos; Tosefes Shabbos 318; M”B ibid]

[3] The reason: Being that it is impossible for it to become completely cooked through doing so and it cannot even further cook it, and it rather only retains its heat [Admur ibid; Taz ibid]

[4] Admur 318:14 “It is allowed to seal the lid [of the upper pot] with dough in order to retain its heat if he has dough that was kneaded yesterday [and was designated for this purpose and is thus not Muktzah].”

[5] Admur 257:8 “This only applies if the food was fully cooked, however if it is not fully cooked and is insulated on top of a Kirah (that has had its coals swept), then it is forbidden to even add on to the cover, as this addition causes to speed up the cooking due to the coals.” Admur 254:4 “[Furthermore] even if one insulated it from before Shabbos near a hot pot which was wrapped with clothes or with other items which do not add heat, and on Shabbos the covering [of the fruits] fell off, it is forbidden to replace it onto the fruits, if they are not yet completely cooked and the area there is Yad Soledes. Furthermore, it is also forbidden to add another clothing on Shabbos [to the insulation], being that this hastens it to finish cooking on Shabbos.”; See Admur 257:8; 318:14 which rules it is permitted to place uncooked foods that are Yad Soledes on top of an insulated pot; Tehila Ledavid 254:4 establishes the case here to be referring to a pot that is on the fire and is insulated in a permitted way, such as with a board over the top of the pot, and the insulation is thus not touching the walls of the pot; See M”A 257; Shabbos Kehalacha Vol. 2 page 60; Piskeiy Teshuvos 257:7 footnote 53

[6] Based on Admur 257:8; 318:14; [However see 254:4 which rules it is forbidden to place uncooked foods on top of an insulated pot; Tehila Ledavid 254:4 establishes the case there to be referring to a pot that is on the fire and is insulated in a permitted way, such as with a board over the top of the pot, and the insulation is thus not touching the walls of the pot.]; M”A 257; Peri Megadim; Shabbos Kehalacha Vol. 1 p. 230-234 and Vol. 2 page 60; Piskeiy Teshuvos 257:7 footnote 53 that discusses the dispute this matter;

Other opinions: Some Poskim rule it is forbidden to add or reinsulate whenever the food is not fully cooked even if it is not on a source of heat. The reason for this is because the insulation delays the cooling down of the food and during this time the food is able to cook more. [M”B in Biur Halacha 257:4 “Gorem Lah”; Beis Meir; Nehar Shalom; Mor Uketzia]

^[7] Shabbos Kehalacha Vol. 1 p. 230-234

[8] Admur in 257:8 and 318:14; However, see 254:4 which rules it is forbidden to place uncooked foods on top of an insulated pot; Tehila Ledavid 254:4 establishes the case here to be referring to a pot that is on the fire and is insulated in a permitted way, such as with a board over the top of the pot, and the insulation is thus not touching the walls of the pot.

[9] Biur Halacha 257 “Lo Nisbashel”

^[10] Shabbos Kehalacha