HOW TO KASHER
The laws of koshering are quite involved and confounding. There are innumerable Halachik possibilities and outcomes depending on the material being kashered, how it was used in the past, and for what purpose it is now being kashered. Therefore it is critical to have a rabbi direct a person in this process, especially if it is one’s first time kashering.
The goal of this short essay is for a most basic review, and so as to give one information so that they know what to ask their personal Rabbi.
There are two major categories of kashering:
Libun – koshering through heat – it is the process by which one kashers a material through using heat or fire to the point of causing the material being koshered to glow or spark (about 800 degrees)
Hagoleh – koshering through a liquid [water] medium – it is the process by which one kashers a material by using a boiling liquid medium (preferably water)
In addition, each one of these two has subcategories, the most common of which being:
Libun Kal – subcategory of Libun – it is the process of using heat to kasher an item but only so as to create a strong heat throughout the material, without a glow.
Iruy – subcategory of Hagoleh – it is the process of kashering a material by pouring the liquid medium onto the item, as opposed to dipping the material into the liquid medium.
Whenever koshering with Hagoleh the utensil must first sit idle and clean for 24 hours prior.
A utensil of a specific class (e.g. non-kosher; meat; dairy; chometz) that became that class through being used to cook food with a liquid medium (e.g. a pot used for boiling spaghetti), should one desire to kasher it, must have their class removed through the same means by which its current class first entered.
Meaning, a pot that became infused with Chometz through a liquid medium while directly on the stove, must be boiled with water directly on the stove to remove that infusion.
Chometz dishware (metals) should be kashered by submerging them in a (Passover) pot of rolling-boiling water. Should the cold dishware slightly cool down the water, one should wait until the water is in a rolling boil again before removing them. One washes off the dishware with cold water after the kashering.
A pot that one wishes to kasher, yet that will not fit into another pot of boiling water, should (rest for 24 hours and then) be filled to the rim and placed on top of the fire. As it is boiling one should take a hot stone –or the like –and place it into the boiling pot. This will allow the water to spill over the sides, thus koshering any area that came into contact with food.
A material that came into contact with hot chometz liquid, without direct heat or fire (e.g. a countertop that hot chometz soup [liquid] spilled upon), needs only hot boiling water spilled onto it.
In any case where Hagoleh or its subcategories are demanded, Libun Kal would work as well.
Please Note: Modern countertops made of a material that may be kashered (e.g. marble) often comes into direct contact with hot food (e.g. hot spaghetti). In order to kasher our countertops (should they be made of material that can be koshered) one must use both hot water and a hot stone. One’s personal rabbi should be consulted.
When a utensil became a specific class due to direct contact with a class of hot food with no liquid medium (e.g. an oven, b-b-q, TeflonTM frying pan) then Libun must be used to kasher.
There is a debate if Libun may be viewed as pragmatic. Meaning, if an oven’s highest cooking temperature is, say, 500° can one perform Libun at 500° as opposed to the usual 800°, since anyway the infusion could have only occurred at 500°?
The opinion of Rabbi Aaron Kotler of Lakewood was to allow such a pragmatic view of Libun, while Rabbi Feinstein rejected it. According to the latter view, one must always –at the very least –self-clean the oven in order to kasher it.
The minhag of Chabad is to always perform a full Libun on oven, and with a blowtorch.
For Pesach, most follow the more stringent view of Rabbi Feinstein, however they rely on the self-clean mode alone to get the oven to a Libun temperature. Whichever view one follows, a (non-rigorous) cleaning with Easy-OffTM (or the like) should be done beforehand.
Not every type of material may be koshered for Pesach. One’s Rabbi must be consulted for a complete list of materials that may and may not be koshered for Pesach.
As the BVK Passover Guide grows each year, the hope is that, GD willing, we will soon include such a list, along with more detailed information. Whatever the case, this guide does not serve to replace one’s personal rabbi.
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