Utensils that have been used with Hametz should not be used on Pesah unless they first undergo the process of koshering. Although it is possible to kosher a utensil on Pesah, it is far preferable to do this before the holiday, as the process is simpler and less complex when done before Pesah.
Before presenting the basic guidelines of koshering cookware, it must be emphasized that not every utensil can be koshered. For example, if a pot has rust or corrosion that cannot be removed, it cannot be koshered for Pesah since it cannot be thoroughly cleaned. Another example is a toaster oven, which cannot be koshered because it is nearly impossible to remove all Hametz particles inside the appliance. Moreover, the basic principle that governs the koshering process is "Ke’bol’o Kach Polto," which means that the Hametz must be purged from a utensil in the same fashion in which it had been absorbed. In the case of a toaster oven, the Hametz is absorbed through fire, as the coils generate high levels of heat. Therefore, the only way to kosher such an appliance would be through direct exposure to fire, such as with a blowtorch. Needless to say, one who tries to blowtorch his toaster oven will likely find himself needing to buy a new one. For this reason, too, a toaster oven cannot be koshered.
Appliances that cannot be koshered do not have to be discarded before Pesah. They should simply be cleaned and put away for the holiday. In the case of a toaster oven, one should clean it as best he could, and although some small crumbs might still remain, he may nevertheless keep the appliance in his home over Pesah, put away in a cabinet until after the holiday.
If one has an appliance that is used with fire which can handle Libun (direct exposure to fire), one should apply fire from a blowtorch to the utensil until sparks emerge from it. Many organizations today run public koshering sites where large, industrial blowtorches are available for this purpose.
Pots placed on the stove do not require Libun, since they are not placed directly in fire. Instead, they are koshered through Hag’ala – immersion in hot water. This means that a large pot is filled with water and brought to a boil, and one then inserts the pot he wishes to kosher into the large pot as it boils. It suffices to immerse the pot for just a moment. It is customary to place the pot in cold water after the immersion. According to Sephardic custom, one may use for this purpose a large pot that had been used with Hametz, and that large pot may then be used for Pesah. (In a separate context we will address the situation of a large pot which one wishes to immerse and it does not fit into any other pots.)
As mentioned earlier, pots with rust or corrosion that is not removable cannot be koshered for Pesah.
It should be noted that nowadays, when cookware is relatively inexpensive, it is preferable to simply purchase a separate set of cookware for Pesah, as this keeps the process very simple and avoids potential problems. Some people also build a separate Pesah kitchen in their homes, which is certainly an admirable practice. Needless to say, not everyone is in a position to have a separate kitchen, but if one can at least purchase a separate set of cooking utensils for Pesah, this would certainly be advisable and praiseworthy.
