We have explained that on Pesach, one must use vessels and dishes that have not absorbed Chametz, meaning either new vessels (or vessels designated specially for Pesach use) or vessels that have been koshered for Pesach. Usually, the way to kosher a vessel is in the same manner it is normally used.
Regarding plates and bowls that hot foods are placed in but are not used as a real “Keli Rishon” (i.e. a vessel with boiling hot liquid directly on the fire or heat source), meaning that when food is placed in them, it is usually dished out of another pot (and this pot was the “Keli Rishon” where the water was actually boiled), their koshering process is in the way it is used, i.e. through pouring boiling water on them from a “Keli Rishon” (for instance, from an electric kettle that water was boiled in). Certainly, these items may be koshered through “Hag’ala,” meaning immersing them into boiling water in a “Keli Rishon” where the water was boiled.
Regarding pans that are used to fry Chametz foods in oil, there is a disagreement among the Poskim whether it can be halachically considered like a pot that Chametz foods are cooked in and Hag’ala will be sufficient or since not much liquid is used to fry foods in it, it should have the halachic status of skewers which require “Libun,” torching with fire. The custom of Sephardic Jewry is that Hag’ala is sufficient for frying pans, while the Ashkenazim customarily require Libun with fire for these pans. Maran Rabbeinu Ovadia Yosef zt”l writes that even according to the Ashkenazi custom, it is not necessary to fire up the pan to such a degree that it turns red-hot; rather, a light Libun, i.e. that it becomes hot enough from the fire that if a straw would come in contact with the pan it would burn, is sufficient.
Any vessels not used with hot foods or liquids, such as silver goblets, refrigerators, and freezers, do not require any koshering and a thorough cleaning is sufficient.
Vessels made of pottery are unable to be koshered; even if they were to be torched with fire very well, they would remain in their forbidden state. According to Maran Ha’Shulchan Aruch, glass vessels need no koshering and washing it well will be sufficient. However, Ashkenazim customarily act stringently regarding glass vessels. Even according to the custom of the Sephardim, porcelain vessels are treated as pottery and cannot be koshered.
It is preferable, whenever possible, to perform Hag’ala on vessels needing koshering only after they have not been used for twenty-four hours. It is permissible to perform Hag’ala on meat and dairy vessels one after another when the Hag’ala is being done in a large pot.
