A. Leaving, Replacing, and Placing Food
C. Placing Foods on a Hot Plate Not in Operation
The most common device for keeping food warm on Shabbat today is the electric hot plate, called in Hebrew a "platta", which consists of a covered heating element, without controls to regulate the heat. Several halachot need to be clarified concerning its use. I do not intend to cite all opinions already in print and will surely not attempt to render a decision in those questions whichare a matter of dispute. My purpose is to clarify the halachic problems involved and perhaps shed some light on them. The permissibility of utilizing electricity generated in power stations operated by Jews on Shabbat will not be dealt with here. This very complicated question demands an extensive examination of its own. This article assumes that the electric current itself does not present any problem.
A. Leaving, Replacing, and Placing
1. Leaving Food on the Hot Plate Before Shabbat
The Shulchan Aruch (OH 253,1) rules:
“It is forbidden before Shabbat to leave a pot on a stove... fueled with gefet, which is the dregs of olives, or with wood, unless the food is completely cooked (before Shabbat) and (continued cooking) spoils it. (Under those conditions) there is no fear that he might stir (the fire). However, if it is only partially cooked, or if it is completely cooked but is improved (by continued cooking), we are apprehensive lest he stir; and it is forbidden to leave the pot on the fire, unless he has removed all the embers (grufa) or covered them with ashes (ktuma) in order to reduce their heat. Another opinion is that it is sufficient if the food is cooked to the measure of ben-Drusai or completely cooked, even if it is improved by further cooking and even if the embers are neither removed nor covered. Removing or covering the embers is only necessary where the food has not been cooked to the measure of ben-Drusai, or where he wishes to return the pot to the fire on Shabbat after it was removed.” Rama; “The custom is to follow the second (lenient) opinion.”
Our first assumption, when analyzing the status of the hot plate in respect to these halachot, is that electric heat, i.e. the heat emitted by the elements of the hot plate, is considered to be "unremoved" (not grufa). This is already mentioned by the Chazon Ish (Hilchot Shabbat 38,2). In the hot plate, the heating elements are not visible, but are covered by an aluminum or enamel sheet. The question therefore is whether this sheet converts the device into a covered (ktuma) fire. The Magen Avraham (253,3) states that it is not necessary to cover a fire with ashes to such an extent that the fire is extinguished. Any amount of covering is sufficient, even if the fire reignites afterwards, since once he indicates that he does not require the embers we do not fear that he will stir them. In other words, an action is done to the embers themselves which constitutes a "sign" (hekeira) that he is not interested in a large fire; as a result, the prohibition based on the fear that he will stir the embers is cancelled.
What is the halacha when a covering is not placed on the embers or on the fire itself, but at some distance above it? Is the fire considered to be ktuma in such a case as well? The Mishna Brura (Beur Halacha, 253, s.v. "Litein") proves from a comment of Rashi (Shab. 37a, s.v. “Gaba”) that such a cover is not ktuma. On the other hand, he infers from a passage in the Rambam (Hilchot Shabbat 3,4) that any form of covering is sufficient. The Chazon Ish (37,9) disputes the validity of this inference. We do, however, find an explicit case of ktuma where the covering is not actually on the fire. "One who awakens and sees that his food is spoiling, and he wishes to prevent further spoiling, may place an empty pot on the stove and then place the pot of food on top of the empty one." (Shulchan Aruch, 253,3) The Magen Avraham (31) explains "the stove is then considered to be grufa u'ktuma, since the pot seals the mouth of the stove; therefore it is permissible to place the pot of food on it, since it is permissible to return food to a grufa u'ktuma stove." The Chazon Ish, however, claims that an empty pot is effective only because "it is a change (from the customary manner of cooking - shinui), and it also greatly reduces the heat, but (with) a cover which is normal and does not significantly reduce the heat, it is considered to be (cooking) directly on (the fire)." In other words, the Chazon Ish agrees that it is not necessary to cover the fire directly, provided that the result is an "unusual" manner of cooking or heating, like the empty pot.
From this point of view, there are two possibilities. There are those who claim that the metal sheet of the hot plate is a cover which is not normally used to cook on, and therefore the hot plate is considered ktuma. This is highly questionable. It is reasonable to assume that only a separate unit constitutes a cover of the stove. If the cover is an integral part of the stove, it itself becomes part of the heating element. On an electric stove, the heating elements (electric coils) are covered with an iron coating; nonetheless, the stove is undoubtedly not considered to be ktuma. Rather, the coated coil is considered as one element. Similarly, the hot plate as a whole should be considered to be one heating element, and not a covered fire. I subsequently found this argument in the Responsa Yaskil Avdi (5,34 and 6,15). Although he permits the use of the hot plate in another responsa (7,28,8), this is for a different reason, which we will consider below.
The accepted reason for permitting the use of the hot plate is that the heat cannot be regulated. Since the reason for the prohibition to use a stove is based on the fear that he will stir the embers, it does not apply to the hot plate where this cannot be done.
There are two possible objections to this line of reasoning.
Firstly, it is possible that although the reason for the rabbinic enactment was the fear of stirring, the prohibition holds even in the case of a stove where stirring is impossible, due to the principle of "the sages do not allow distinctions" (Lo plug rabbanan). The opinion of most authorities today, however, is that this enactment does not hold where the reason for it does not apply. The Har Tzvi (OH 1,136) bases this conclusion on a ruling of Rav Akiva Eiger (OH 318, on the Magen Avraham, 10) that it is permitted to leave food on heated objects (where the fire is no longer present). This proof is questionable. A heated object is not an ember and therefore is even more grufa (removed)than a grufa stove. In our case, there is an uncovered fire, although the possibility of stirring the embers or fanning the flames does not exist.
Another possible proof for the lenient view is the case of the empty pot (quoted above), which indicates that if there is a “sign” that demonstrates that there will not be stirring of the embers, it is permissible to use the stove, although it is not considered to be covered (according to the Chazon Ish). But this also is not conclusive. The Magen Avraham states that this stove is considered to be grufa u’ktuma. Apparently, we view the empty pot as accomplishing the same effect in relation to the fire as would covering the embers with ashes; that is, it is considered to be ktuma. If, however, there is no cover at all, though for some other reason it is impossible to stir the embers, the stove is not ktuma and the enactment may apply. However, from the continuation of the Magen Avraham it appears otherwise. He quotes the ruling of the Maharil that one may place a pot on a stove with a separation between the pot and the fire, and the ruling of the Tashbetz that the placing of any object on the stove which will serve as a "sign" is sufficient. The Mishna Brura (Shaar Hatziyun, 253, 75) explains that the purpose of the “sign" is to indicate that he does not desire much heat, and therefore it is not likely that he will stir the embers underneath the cover. From this it is clear that there is no need to smother the embers. Even if the fire is uncovered, if there is a sign which eliminates the likelihood of stirring the embers, the stove is considered to be ktuma. Therefore, the hot plate, where the possibility of “stirring" does not exist at all, may be considered to be equivalent to a grufa u’ktuma stove.
2. Replacing and Placing
We face, however, another problem. The possibility of stirring the embers is the reason for the prohibition to leave partially uncooked food on the fire before Shabbat. The prohibition of replacing cooked food on an uncovered fire after it has been removed on Shabbat may be based on a different reason. The Mishna Brura (ibid. 37) quotes Rashi and the Ran who explain that replacing is forbidden because it resembles cooking (“michze kemevashel”). In the Shaar Hatziyun (ibid. 37), he quotes the Sefer HaYashar who explains that a covered fire is necessary because he may stir the embers when the pot is returned in order to reheat it, since it probably cooled off during the time that it was not on the fire. Accordingly, if the reason is the fear of stirring, the hot plate will be permitted, as explained above. However, if the reason is the resemblance to cooking, we must determine if this reason applies to a hot plate. We will first examine the assumption that the prohibition of replacing is based on the resemblance to cooking.
Aside from the prohibitions of leaving and replacing, one is forbidden on Shabbat to place on the stove a pot not previously on the fire, even if the contents are fully cooked, and even if the fire is grufa u'ktuma. (cf. Rama, 253,5; Biur HaGra, ibid. s.v. "Mutar"; Pri Megadim, Eshel Avraham, 33; Mishna Brura, 87). This reason for this prohibition is unquestionably because this action resembles cooking (see the above cited commentators). It follows from this halacha that the possibility of resembling cooking exists even in a grufa u'ktuma stove. If returning is prohibited because it too resembles cooking, it should also be prohibited in the case of grufa u'ktuma. But this is not the case. It is permitted to return a pot to a covered stove - in fact, according to the second opinion quoted by the Shulchan Aruch and accepted by the Rama, this is the principal halachic consequence of covering the stove. (The Rama accepts the opinion of Hanania that leaving a pot on the fire before Shabbat is permitted even on a uncovered stove. The covering is necessary to allow returning a pot on Shabbat itself, once it has been removed.) The answer is that according to Hanania who allows leaving food on an uncovered fire, we apparently do not normally worry about the possibility that he may stir the embers. Nonetheless, returning a pot on Shabbat is forbidden, since in a situation that resembles cooking, we prohibit the action lest he stir the embers. In other words, according to the Rama, returning is forbidden because it resembles cooking, but only when there exists a possibility of stirring. Placing a pot for the first time on the fire is forbidden because it resembles cooking even when there is no danger that he will stir the embers. Hence, if we agree that the hot plate is not included in enactments based on the apprehension of stirring, it will be permitted to return a pot to it on Shabbat, but not to place a pot on it for the first time.
Another reason for permitting the use of the hot plate on Shabbat is found in a number of sources, including the latter responsa in the Yaskil Avdi, quoted above. It is argued that since the hot plate (in the case of the kind sold in Israel) is intended and constructed for use only on Shabbat, this itself constitutes the clearest “sign”, and therefore it may be used both for “leaving” and “replacing”. Another argument is that since the hot plate is intended only for preserving the heat of warm food and is never used for cooking, placing a pot on it cannot be said to resemble cooking under any circumstances. According to this line of reasoning, even if the prohibition of replacing is because it resembles cooking and not because of the fear of stirring, the hot pot may still be used. In fact, according to this argument, it will even be permitted to place on the hot plate, food not previously heated on Shabbat, provided that prohibition of cooking does not apply. This indeed is the ruling of Rav Ovadia Yosef (Yechave Daat, 2,44).
This conclusion may be disputed. Even if we accept the first argument, that the hot plate is considered to have a “sign”, the second assumption, that using it does not resemble cooking, is not as clear. The Gra, in the passage cited above, states that “even though it is prohibited to replace on an uncovered stove and to place for the first time even on a covered one, even something hot and fully cooked, this is only where it resembles cooking in the normal manner. To put food in a pot that is not on the fire (kli rishon), or to place the pot indirectly in front of the fire, is permitted, as most people do not generally cook in this manner. It does not resemble cooking, but only warming up. It is only prohibited (in this manner) where it might lead to actual cooking."
By this definition, the hot plate does not resemble a “kli rishon” or a pot placed indirectly in front of the fire. It is true that most people do not use the hot plate to cook, but this is because they have stoves which are more efficient. It is definitely possible to cook on the hot plate as well. In the case of cholent, it is common practice to leave the pot on a hot plate when it is only partially cooked, and allow it to cook slowly overnight. Therefore, it seems reasonable to conclude that the reason of resembling cooking applies to the hot plate. Anything that is forbidden because it resembles cooking will be prohibited on the hot plate, while things that are prohibited because of the fear of stirring are permitted.
The Shulchan Aruch (OH 257,1) states; “One may not cover with something that produces vapors, even before Shabbat.” Later (ibid. 8) he adds; “Although it is permitted to leave a pot on a stove with embers within using one of the methods described in Sec. 253, if it is covered by cloths which produce vapors because of the fire, even though the cloths do not produce vapors on
their own, it is forbidden.” It sometime occurs that one wishes to cover a pot on the hot plate with various materials in order to better preserve the heat. We must determine the status of the hot plate in relation to this prohibition.
The reason for the prohibition of hatmana is given in Shabbat (34b). "Why may one not cover with something that produces vapors? It is an enactment lest he cover with remetz (Rashi - 'ashes mixed with embers'). Abaye asked, Let him do so! (Answer -) It is an enactment lest he stir the embers." Although we have seen above that the possibility of stirring is not present in the hot plate, this will not be sufficient reason to permit hatmana with a hot plate. The Shulchan Aruch (ibid. 3) lists many materials included in the enactment of hatmana despite the lack of a possibility of stirring. The reason is that all hatmana is prohibited because of the possibility that he will cover with remetz. Therefore, the hot plate is included in the general prohibition against all hatmana.
C. Placing Foods on the Unit When it is not Operating
It is possible to connect the hot plate to a timer ("Shabbos clock") which will switch it on during Shabbat. Is it permissible to place a pot on the unit when it is switched off, so that at a later hour the food will be heated automatically?
The Trumat HaDeshen (66) writes;
"It is not permissible for a Jew... to place the cholent on the stove, and the (non-Jewish) servant will afterwards light the stove. This is (comparable to the case of) 'one brings the pot and one lights the fire' where the first one is not punished but it is prohibited (rabbinically).... This is comparable to what is written in the Mordechai in the first chapter of Shabbat, that it is forbidden to leave food in the courtyard before a non-Jew if it is known that the non-Jew will definitely take it out (and transfer it to another domain, which is prohibited on Shabbat). "
The passage in the Mordechai is as follows:
"The Riva ruled that (it is only permissible to place objects in the courtyard) in the case of foods which can be eaten in the courtyard. However, it is prohibited to place things which are normally transported from place to place, even according to Bait Hillel. Beit Hillel only permits this when it is done before Shabbat, so that the object is not in the Jew's domain before Shabbat.... On Shabbat it is forbidden, as it appears that the non-Jew is transporting (it) as an agent of the Jew." (Mordechai, Shab. 1,253)
Since the reason for this prohibition is that the non-Jew appears to be an agent for the Jew, it only applies to a human agent. In the case of an automatic action, controlled by a pre-set clock, there would be no reason to forbid it. The first case quoted by the Trumat Hadeshen, that of 'one brings the pot and one lights the fire', is also not relevant to our case. The Beit Efraim (quoted in Shaarei Tshuva, 253,24) points out that in that case the fire is lit by a Jew. In such a case, the first Jew is indirectly responsible for the actions of the second. (cf. Tosafot, Shab. 3a, s.v. "Lava"). Therefore, it is permissible to place a pot on the hot plate when it is not operating.
However, the Har Tzvi (OH 1,136) disagrees.
"If, on Shabbat, one places a pot on an electric stove which will later operate automatically without any human action, it is comparable to a case of placing a pot in a location where the fire will eventually be present... which is a Torah prohibition according to the Tosafot in Sanhedrin (Via, s.v. "Sof Chama"). In this case, where the current is already present when he brings the pot to the stove, and it will enter the stove automatically..., it is comparable to bringing the pot to the fire, which is a Torah prohibition.... In the case of the Trumat HaDeshen, there is no Torah prohibition... because the fire is not yet existent. The fire of the wood that the non-Jew lit afterwards was not existent when the pot was placed (on the stove). In our case, however, the electric current may be considered to be already existent, and it is destined to enter the stove on its own through the operation of the automatic timer."
This conclusion appears to be unwarranted. It is clear that the electric current which is obtained from the general grid is produced at precisely the second that it is being used. Hence, the current that will eventually activate the stove does not exist at all at the time that the pot is placed on it. This is also the conclusion of the Chazon Ish (Shab., 38,3). He raises the problem of the rabbinic prohibition of placing foods on a stove on Shabbat. Since at the time of the placing of the pot, the hot plate is cold, there is no reason to see this as "resembling cooking". Cooking is never done without heat. Hence, if there is no problem of leaving and replacing, as explained above, there is also no problem of placing.
 Defined variously as one-third or one-half of normal cooking. - trans.
 cf. Shmirat Shabbat Kehilchata, 2nd ed., 1,25. - ed.
 When a rabbinic enactment is made for a particular reason, it holds in all roughly similar cases, even if the original reason does not apply, as the sages do not wish the Halacha to be based on subtle distinctions not always apparent to the average person. – trans.
 Hatmana -covering a pot completely on all sides in order to seal in the heat is forbidden on Shabbat. - trans.
 The Shmirat Shabbat Kehilchata (2nd ed., 1,26) follows the ruling of the Har Tzvi. The point raised by the author depends on whether we consider the current itself, which is continually being produced, or the source of the energy, which is existent all the time. The basis of the Har Tzvi's ruling is the case in Sanhedrin of "the sun will arrive". There too ,one can say that the energy that will eventually arrive from the sun is produced at a later moment. The sun, however, is always existent. Similarly, the power station is always existent. It is true that the power could be cancelled by human interference, unlike the sun. However, since it presently is automatic and there is no reason to assume that it will be cancelled, it appears comparable to the case of "the sun will arrive". - ed.