Basya Tsybukmakher
The Prohibition of Insulating Food – How Do You Warm a Bottle of Baby Food Correctly?
Let us consider another relevant question: insulating food within other food or inside a pot containing other food. A homemaker often wants to prepare cholent or a roast, along with a side dish cooked in a special sealed, heat-resistant bag inside the main dish. The reason may simply be culinary preference. But this raises a question: does cooking rice or pearl barley in a bag inside a pot constitute forbidden insulation? After all, there is direct contact on every side, and heat is being added during Shabbat. Here is another example: you need to warm cold baby food, milk, or something else. How do you do it? You take a deep bowl, pour boiling water into it, and place a bottle or jar of baby food inside. But what about insulation? Here, too, the water is in contact with the container's sides, and heat is being added.
Let us examine this in more detail.
First, we need to determine whether insulating food in a liquid that is cooling is forbidden.
The Beit Yosef (section 258) has already established that this does not constitute insulation. In other words, whenever someone wishes to take a pot off the fire and place another, cold pot—for example, containing water—on top of it, this is not considered insulation that adds heat. Why? Because this arrangement is cooling and losing heat, it does not fall within the prohibition of insulating.
On the other hand, the Talmud states (Shabbat, 48a) that on Shabbat it is forbidden to place a jug of cold water on a kettle of hot water, even if the kettle has already been removed from the fire. How are we to understand this? The Rishonim explained that this prohibition differs from the standard prohibition of insulating, since the arrangement is cooling. However, there is a separate prohibition against generating heat in something cold, which resembles the prohibition of insulating with material that adds heat. This new prohibition applies only on Shabbat, not before it.
Another important point: the Talmud (Shabbat, 40b) permits placing a jug of liquid in a second vessel to warm it during Shabbat (without violating the prohibition against cooking). It states that olive oil intended for rubbing into the skin may be placed in a bath to bring it to a pleasant temperature. But what about the prohibition of insulating? The bath is filled with hot water. Even though it is a second vessel, the water surrounds the sides of the jug of oil and generates heat in it on Shabbat itself. Why does this not fall under the prohibition described above?
There are two main answers to this question:
1. If the jug is not completely submerged in the water, then according to the rabbis who permit partial insulation, the explanation is as follows: the jug protrudes from the water, so this does not constitute insulation.
2. The Chazon Ish, who forbids partial insulation, held that the Sages' prohibition of insulating does not apply at all inside a pot of water. What is forbidden is placing a jug on top of a pot and insulating the entire arrangement to retain heat or generate heat in the cold pot (but only if the arrangement retains the form of insulation). In this case, however, it is simply warming.
It follows that, when we consider whether insulating food within other food or liquid is forbidden, according to the Chazon Ish it is never forbidden.
But on this question, as in most cases, we primarily follow the opinion of the Rema and the “Mishnah Berurah”—partial insulation is not forbidden. In this example, however, that means it does constitute insulation. In other words, if food in a bag or another pot (or bottle) is completely covered by water or other food, it falls under the prohibition of insulating and requires compliance with all the associated laws.
(An important general observation is needed here concerning our understanding of which rabbis are stringent and which are lenient. Remember that we wrote that, according to the Chazon Ish, partial insulation is forbidden, which is clearly a stringency, whereas according to the “Mishnah Berurah” it is permitted, and the Chafetz Chaim is lenient. But in our case, everything is reversed. Since the Chazon Ish cannot explain the Talmud's example on the basis of partial insulation, which contradicts his position, he offers another explanation for the Talmud's permission. The “Mishnah Berurah” does not need such an explanation, and therefore, according to his opinion, all the restrictions governing insulation apply. We can see that there are no lenient or stringent opinions; each individual sage has a clear understanding of the law!)
It is clear, however, that our entire discussion concerns only a pot that is not on the fire. If it is on the fire, placing food inside it would be forbidden because of the prohibition against placing food on the fire on Shabbat, rather than because of the prohibition of insulating.
Practical Conclusions
1. On Friday, one may place a bottle of cold water or milk inside a pot of hot water.
2. If you want to do the same on Shabbat, leave a substantial part of the bottle uncovered by the water.
3. The hot water must be in a second or third vessel only; otherwise, warming is forbidden because it violates the prohibition against cooking.
4. According to Rabbi Shlomo Zalman Auerbach, on Friday one may put grain in a heat-resistant bag and place it inside a pot of cholent to cook, even if it is completely submerged in the food. Rabbi Shlomo Zalman held that this is a method of cooking, rather than a method of insulating. In this way, a person places two dishes on the fire, but in a single pot. The cholent surrounding the rice does not serve as thermal insulation; it simply makes it possible to place the rice on the fire, thereby saving space on the hotplate or allowing the cholent and rice to cook separately without mixing. Rabbi Elyashiv held that it is preferable to make small holes in the bag so that the cholent and grain constitute a single dish if we want to submerge the grain completely in the food, since outwardly this looks like insulation. Rabbi Ben Zion Abba Shaul followed Rabbi Auerbach's opinion, while Rabbi Yitzchak Weiss and Rabbi Shmuel HaLevi Wosner—may the Almighty lengthen his years—shared Rabbi Elyashiv's opinion. Therefore, on this question, everyone has an authority on whom to rely.
5. According to all opinions, even that of the Chazon Ish, a heat-resistant bag containing grain may be partially submerged inside a pot.