Glow Sticks and Microwave Ovens
During Shabbat I was thinking a bit more about the questions of glow sticks on Shabbat (see here) and I found some similarity to the question of whether one is permitted to use a microwave oven on Shabbat. How is a posek suppose to approach the question of using a microwave oven on Shabbat? Poskim inevitably discuss the sources from Talmudic and post-Talmudic literature that address cooking with fire, the sun, etc. But where does a microwave oven fit into all of this? Rabbi Moshe Feinstein (Igrot Moshe, OH vol. 3, no. 52) seemed to think that since a microwave oven is used to cook in a similar way to the way that fire is used, even though it is different from the way cooking was accomplished in the mishkan, it should be prohibited biblically.
A narrower reading of the sources can be found in Rabbi Yitzhak Yosef’s discussion in Yalkut Yosef, Laws of Shabbat, vol. 3, pp. 150-155 (in my edition). Rabbi Yosef shows that the way the cooking is done in a microwave oven is different than the way that it was done in the mishkan, therefore it should only be prohibited rabbinically. The practical implications of assigning a rabbinic prohibition relate to situations such as a sick person whose life is not in danger, asking a non-Jew to use on Shabbat, etc. A more in depth discussion of the microwave oven in halakhah can be found in a article by Prof. Zeev Lev in Teḥumin, vol. 8, pp. 21-36. Prof. Lev critiques Rabbi Feinstein’s approach and holds that the use of a microwave oven on Shabbat is prohibited rabbinically.
Rabbi Feinstein seemed to be interpreting the spirit of the law, presenting a somewhat teleological approach, if it cooks, then it’s cooking. This led him to a stricter interpretation than someone who might read the sources in a narrower fashion. As an aside, this is an example when the “spirit of the law” is not necessarily more lenient, something that many liberal halakhists seem to forget.
June 13th, 2010 at 11:53 pm
The concept of ‘melekhet mahshevet’ often leads to a teleological approach – there are a number of examples where the concept helps overcome an apparent deficiency in the ‘act’ to render it biblically forbidden. There’s a dispute between Rashba and Ran regarding whether the deficiency of ‘hak tokhot’ applies to the biblical prohibition of writing on Shabbat; this would seem to have implications on whether typing or texting is a biblical-level violation. Here, too, the ‘spirit’ of the law is stricter.
June 14th, 2010 at 12:14 am
Why aren’t there two considerations here? 1) Operating an electrical device on Shabbat. This one, btw, usually has a pretty standard motor rotating the tray. The consensus probably is that is forbidden on Shabbat, even though the poskim don’t clearly agree on what m’lacha is being done. 2) Cooking on Shabbat, which you’ve addressed. It seems you still can’t get around (1); unlike, say, the use of magnaesium heaters to heat LaBriute or other MRE type meals. No?
June 14th, 2010 at 6:11 am
Mordechai,
I also thought about LaBriute meals, but I wasn’t able to find any discussion about using them on Shabbat. Rav Moshe’s actual discussion of Microwave ovens is fairly short and he doesn’t really address the question of electricity, he focuses on bishul. In Yalkut Yosef there is a long discussion of electricity and he holds that unless there is an incandescent bulb it is only a rabbinic prohibition.
June 14th, 2010 at 12:25 pm
Setting aside the question of the electric circuit itself, I believe the following analysis holds true.
Rav Moshe Feinstein (Igerot Moshe Orech Chaim 3:52) explains, based on Rashi and the Ran, that bishul chama is permitted because it is not the normal way of cooking. He explains that it is not a form of shinui, like kilachar yad, rather it is an uncommon form of cooking. One would only cook in the sun when one does not have any wood available. He then argues that since cooking in a microwave is an effective way to cook and those that have them do a lot of cooking in them, it is to be considered a normal way of cooking. It seems to me that one could question the assumption that cooking in a microwave is to be considered a normal way of cooking. When the teshuva was written in 1971, Rav Moshe seems to be under the assumption that it is only a matter of time before everyone will own a microwave and use it to cook food. While it is technically possible to cook in a microwave, most people only use it only for defrosting or reheating. In many ways it has become similar to the way R’ Moshe describes bishul chama. One would only cook in microwave if a standard stove (i.e. bishul aish) was not available to them.
Rav Shlomo Zalman Aurebach (Minchat Shlomo 1:12) discusses the case in which one cooks food by running an electric current through it. Since electricity is not considered aish, this form of cooking is toldot hachama. Rav Shlomo Zalman does not explain conceptually why this form of cooking is considered toldot hachama and not bishul hachama, however in the case of a microwave it is easier to understand why this is the case. The microwaves emitted do not actually cook the food. Instead they excite water molecules in the food which heat up and cook the entire piece of food. This would make them toldot hachama.
A La Bruite food warmer works by creating a chemical reaction with generates heat and is used to cook a prepackaged meal. It would seem that according to the approach of R’ Moshe regarding microwaves, this could be considered like bishul chama because it is not the normal way of cooking. One specifically would only cook in this manner if the standard alternatives were not available. It is typically only used when one is camping or traveling. If so this could be considered to be like bishul b’chama and even potentially permitted. According to R’ Shlomo Zalman, the chemical reaction would not be considered a form of aish, however it is unclear what exactly is cooking the food.
It seems that it is a combination of the water and heating element that both become hot and cook the food. If so, it would be considered bishul b’toldot hachama.
A La Bruite food warmer works by creating a chemical reaction with generates heat and is used to cook a prepackaged meal. It would seem that according to the approach of R’ Moshe regarding microwaves, this could be considered like bishul chama because it is not the normal way of cooking. One specifically would only cook in this manner if the standard alternatives were not available. It is typically only used when one is camping or traveling. If so this could be considered to be like bishul b’chama and even potentially permitted. According to R’ Shlomo Zalman, the chemical reaction would not be considered a form of aish, however it is unclear what exactly is cooking the food.
It seems that it is a combination of the water and heating element that both become hot and cook the food. If so, it would be considered bishul b’toldot hachama. I would probably be strict to assume that at the very least this case would rabinically prohibited. (See Yalkut Yosef 318:19 footnote 19 in which he specifically addresses Labruite style cooking).
June 14th, 2010 at 2:31 pm
Zach, a good comment; but I question your assertion about how ‘most’ people use a microwave. I suppose maybe we need some statistics; because my observation is different from yours. I often see that it is used for a wide range of things, depending on what is easiest. Folks cook what is easy to cook, reheat what is easy to reheat, and leave some other items for the stovetop or oven. For that matter, Raytheon and Litton developed microwaves to be the sole source for cooking in environments like submarines. (I remember this because a neighbor when I was a child worked in New London and had an early microwave in his home.)
Your assumption is pretty important to your understanding of the halacha, and since it is a dfference between a d’oraita and a d’rabbanan, it probably needs to be better substantiated.
June 14th, 2010 at 2:43 pm
Along the lines of how do people cook, I remember that R. Yitzhak Yosef commented in Yalkut Yosef that except for some people who work for the Israel Electric Corporation, who then didn’t have to pay for electricity, people don’t use a “plata” (hot plate) for cooking, rather, most people use it for reheating.