Through Fire and Water
BY: RABBI YECHIEL TEICHMAN
INTRODUCTION: The Torah relates כל דבר אשר יבא באש תבא באש¹ that utensils that were obtained during the war against the Midianite nation needed to be kashered. Even after one has washed the surface of the utensil and it appears to be clean, the Torah teaches that there is some absorbed residual flavour. Utensils obtained from non-Jews presumably were used to cook non-kosher meat and the utensils therefore must be kashered to purge them of the non-kosher flavour residue.
TWO METHODS OF HEATING: Halacha prescribes specific methods for kashering utensils, depending upon how they were used with non-kosher food.² If the non-kosher food was cooked in a liquid, the prescribed method of kashering is hagala – boiling water. If the non-kosher food was cooked or baked as a solid directly on the utensil over a heat source, the prescribed method is libun i.e. fire. This rule is described as k’bolo kach polto – the same manner that it was absorbed, it will be purged.³
ABEYANCE PERIOD: When hagala is used, the non-kosher taste is removed from the pot through boiling water. This taste is now in the hagala water, and, if re-absorbed in the pot, will render the pot non-kosher. The solution is to wait 24 hours before kashering.⁴ After 24 hours the taste is considered stale and will not render the pot non-kosher if it is re-absorbed. When libun is used, the absorbed taste is burned out of the pot. There is therefore no concern of re-absorption, and a 24 hour abeyance is not required.
EARTHENWARE: Metal, wood, and stone utensils are able to be purged of the absorbed flavours by boiling in water.⁵ Earthenware cannot be fully purged by boiling in water. These utensils will continue to leach out flavour during subsequent use, and therefore cannot be kashered in this manner.⁶ Libun on earthenware is only effective when it is heated by placing the heated coals within the utensil and is only allowed to be used when that is the normal usage such as an oven. If it is not the normal use, such as a pot or bowl, chazal did not allow kashering with libun out of concern that a person not wanting to risk breaking the utensil will not allow it to heat up sufficiently. If the earthenware utensil was placed in a kiln and allowed to reach kashering temperatures this is an acceptable kashering. By placing the pot in a kiln the owner has demonstrated that he has no concern about the pot breaking.⁷
LIBUN IN PLACE OF HAGALA: Libun is a higher level of kashering which works for utensils requiring hagala, a lower level of kashering. There is an in between level of kashering called libun kal. Libun kal also uses direct heat to kasher, but it does not reach as high a temperature as libun. While libun is defined as heating until the metal sparks⁸ (approx. 454°C/850°F), libun kal is defined as heating until it is hot enough to burn straw (approx. 232°C/450°F). Whenever hagala is required one may use libun kal as an alternative.⁹
KASHERING ON YOM TOV: Poskim do not advise kashering on Yom Tov because kashering involves the melachos of havarah, making a fire, and potentially bishul, heating water. If hagala is needed for a pot that one would like to use on Yom Tov it is forbidden to heat water to do hagala on Yom Tov, and the hagala must be done prior.¹⁰ The Shulchan Aruch teaches that a griddle that is used for dairy and meat cooking¹¹ must be heated in between uses to burn out the residual dairy or meat taste. The level of heating required is until straw will be burnt.¹² This heating may be done on Yom Tov¹³ provided that this serves as the pre-heat for and immediately precedes the subsequent cooking of Yom Tov food. A griddle that was used for non-kosher may not be kashered on Yom Tov as this would be required to be done at a very high temperature until the metal sparks, and this is considered tikun mana – fixing a utensil.
**LEVELS OF USE:**¹⁴ A utensil that was not used directly on the fire but that had non-kosher liquid poured into it (irui) does not need to be placed in boiling water. It can be kashered by pouring boiling water onto it. This follows the rules of k’bolo kach polto.
Utensils that require hagala are typically immersed in a large pot of boiling water. This means that the hagala is able to reach the whole pot including the rim. A large pot, that needs kashering and cannot be placed within another larger pot of boiling water, can be kashered by filling the pot with water, boiling it, and causing the water to overflow on all sides. Although the rim is only momentarily exposed to the boiling water, this suffices, since originally during cooking when the utensil became non-kosher the rim likewise only absorbed the non-kosher from an occasional splatter.¹⁵ This is another example of k’bolo kach polto.
All of these laws of kashering outlined above are not only employed in the home, but are used by COR and other kashrus agencies around the world every day when kashering large and sophisticated equipment used in food manufacturing facilities. Sometimes it’s though fire, more often it’s through water, but the end result, is that it is always kosher. ∎
Rabbi Teichman is a Rabbinic Administrator and Halachic Advisor at COR
Kashruth Council of Canada | www.cor.ca — 2021 / 5782, Halachic Corner, pp. 8–9
COR, the Kashruth Council of Canada, is one of the world’s largest kosher certification agencies, certifying thousands of products, restaurants, and facilities. Learn more at cor.ca, or read about our certification services at corkosher.com.