It is well-known that when Robert A. Heinlein entitled his most famous novel, “Stranger in a Strange Land,” he adopted a phrase from the book of Exodus. Very often, the kosher consumer feels like a stranger in a strange land. Whether it’s an executive in a hotel during a business trip, or a Ba’al Teshuvah in his parents’ home, kosher consumers must sometimes navigate their way in a nonkosher kitchen. The purpose of this presentation is to offer some points of guidance to those faced with such challenges.
Typically, people like to eat a hot meal. How does one render a nonkosher stove or oven fit for kosher usage?
Typically, kosherizing takes two forms: either the application of boiling water or steam to the nonkosher utensil or the application of dry heat. The use of water or steam is called “Hag’alah” and the use of dry heat is called “Libbun.” The principle that underlies kosherizing is known in the halachic literature as, “K’Bohl’o, Kach Pohlto.” This principle teaches us that the process for kosherizing a utensil involves a recapitulation of the process that rendered it nonkosher. For example, if one cooked nonkosher beef stew in a pot, the process of kosherizing will involve bringing water to a boil in that pot. Similarly, if one fried a nonkosher cheese omelet in a pan, the process of kosherizing the pan will involve the application of dry heat to the pan.
Step one in the customary kosherizing of a gas stove is to clean the stovetop. Then, without removing the grates, turn on the flames full blast for 15 minutes. To kosherize an electric stove, clean the stovetop. Then, turn on the burners, let them get red hot, and keep them at red heat for 5 minutes.
Please note that this discussion does not cover Corningware ranges or glass stovetops.
Kosherizing a conventional oven is a little more involved. First, clean the oven of all residue with an effective oven-cleanser. This includes the racks, the door, and the hinges, as well. If there is any residue that is difficult to remove, it must be evaluated. Is it a mere discoloration? Is it an intangible spot? Then it is no problem. Does the rust have substance to it? Then it must be removed. In case of any questions about residue, further Orthodox rabbinic consultation and investigation is needed. It’s worth noting that oven cleansers are made of chemicals hazardous to one’s health, and as such, need not be kosher-certified. After the cleaning is completed, do not use the oven for 24 hours. At the end of this 24-hour period, turn on the oven with the racks inside and allow the oven to reach its highest temperature. Once it is at its highest temperature, leave it that way for an hour. At that point, the oven and its racks will be kosher. This process is known as Libbun Kahl. It should be noted that the broiler tray would not be kosherized by this method. Unlike the oven racks and walls, the broiler tray has direct contact with food. It requires a process known as Libbun Gamur. Libbun Gamur requires temperatures that are higher than the typical oven’s highest temperature.
A self-cleaning oven is easier to kosherize. Merely run it through one cycle.
The process for kosherizing a microwave oven is somewhat simpler. Remove the glass tray and do not use it for kosher food. Clean the microwave of all residue. When the clean-up is completed, place a cup of water in the microwave. Boil out the water in the cup until the microwave fills with vapor. At that point, the microwave is kosher.
It should be noted that the procedures outlined here do not necessarily apply to kosherizing for Passover.
Of course, it may not be feasible or practical to kosherize an oven. In that case, another course of action must be adopted. There are theoretically three challenges that nonkosher ovens pose for the kosher consumer.
The first of these is the residue on the racks. A kosher tray resting on nonkosher residue can potentially be rendered impermissible. The tray’s contents might also be rendered impermissible. The second issue is Rei’ach, that is to say, aromas. These aromas may come from the residue on the racks or the oven floor. Under certain conditions, aromas from nonkosher food will render kosher food impermissible. The third issue is Zei’ah, that is to say, vapor. Within certain parameters, vapors wafting off of foods in a nonkosher oven can lead to the kosher food becoming forbidden.
How are these three challenges met?
To heat food in a conventional oven, wrap the food in two layers of aluminum foil. The foil wrap will keep the vapor sealed inside, it will block outside aromas and vapors, and it will protect the kosher food from the rack’s nonkosher residue. Indeed, the nonkosher residue may render the outer layer nonkosher, but in the absence of a liquid in-between the layers, this forbidden outer layer will neither compromise the kosher status of the inner layer nor of the food inside. In the halachic literature, this concept is known as “Ain HaBeliyah Yotzais MiKeili L’Keili B’Lo Roteiv.”
To preserve the kosher status of food being warmed in a nonkosher microwave, wrap it in two layers of plastic wrap. The OU also advises that all noticeable pieces of food be removed from the spot where the kosher food will rest.
It should be noted that when the halachic literature discusses two layers of foil or plastic wrap, the goal is the two layers. As such, a plastic container with no holes counts as one layer. Similarly, a disposable foil tray covered with a sheet of foil counts as one layer. If any of the layers burst, further Orthodox rabbinic consultation and investigation is needed.
Another challenge that comes up when addressing the issues in a nonkosher kitchen is the use of eating utensils. Nonkosher eating utensils may render kosher food impermissible. Moreover, independent of kashrus concerns, it may still be forbidden to use a utensil if the mitzvah of Tevilas Keilim, immersing utensils, was not performed.
Let us address the kashrus issue first.
If a nonkosher utensil is clean, it may be used on an ad-hoc basis with cold kosher food. For example, if you’re staying in a hotel for a few days, it is permissible to eat cold kosher cereal and milk in a clean nonkosher bowl provided by the hotel. Regular usage could be problematic. For example, inheriting beautiful nonkosher china bowls and deciding to use them for cold fruit soup during Shabbat summer meals. If there is any uncertainty about the distinction between ad-hoc usage and regular usage, further Orthodox rabbinic consultation and investigation is needed.
The issue of unimmersed utensils can be easier to manage under certain circumstances, but in different circumstances, may actually be more difficult. If the utensils are not owned by Jews, there is no need to immerse them. If the utensils are owned by Jews, there is a mitzvah to immerse them and a prohibition against using them until they are immersed. This mitzvah and this prohibition depend on what they are made of and how they are used. There are, however, some well-predicated emergency measures within the halachic system, elucidated by the only people qualified to promulgate such leniencies: our sages. For example, the great sage Rav Moshe Feinstein asserted that in a time of great need, an unimmersed utensil may be used if the food in question could theoretically be eaten without the utensil. For example, common decency and manners require one to eat steak on a plate. In theory, however, it is possible to eat steak without a plate. On the other hand, there is no way to eat soup without a receptacle. Following Rav Feinstein, a person could use the steak-plate in a time of great need but not the soup-bowl. The great sage Rav Moshe Sternbuch maintains that a glass utensil may be used if it is very, very necessary to do so, even if it is unimmersed.
It should be stressed that these citations from Rav Feinstein and Rav Sternbuch apply only to the issue of immersion and not to the issue of kashrus.
It is worth noting that most authorities rule that plastic utensils do not require immersion. Paper utensils do not require immersion, either. The status of glazed earthenware is a subject of dispute among contemporary authorities. Rav Moshe Feinstein maintained that the typical piece of glazed earthenware does not require immersion.
Let us close with a lesson inspired by the Bible. The book of Esther contains the one and only Biblical appearance of the word “kosher.” Queen Esther uses the phrase, “V’Kasheir HaDavar,” meaning, “and the matter is fitting.” This phrase can also be understood as, “and the word is kosher.” Let’s talk about this notion as it relates to filial piety. When dealing with parents, it’s crucial for Jews to remember that their words must be kosher. For example, a parent may pass an unwanted comment about the rearing of their grandchild. A rabbinic mentor may direct a newly-observant Jew to disobey a parent who opposes their new observances. In all families, disagreements may come up, and firm resolve may be required, but let no Jew ever, ever speak in a disrespectful or condescending way to a parent. An observant Jew must always keep in mind: when he or she speaks in the right way, the words are kosher, and he or she thereby increases the Honor of G-d and sanctifies His Holy Name.
Rabbi Ferrell is a Rabbinic Coordinator at the Orthodox Union, and is involved with chemical companies and OU Kashrus education.