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 made of metal or plastic that hot foods are placed in but are not used as an actual “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.
Glass vessels do not require any koshering and according to Maran Ha’Shulchan Aruch, a thorough washing is sufficient for them. The Ashkenazi custom, however, is to act stringently in this regard. We have already discussed this regarding the laws of milk and meat.
There are some Sephardic communities outside of Israel who had the custom to abstain from using glass used throughout the year on Pesach. Nevertheless, Maran Rabbeinu Ovadia Yosef zt”l rules that when these communities emigrate to Israel, they may immediately nullify their customs and observe all rulings and customs based on Maran Ha’Shulchan Aruch. Indeed, even acting stringently against the ruling of Maran in Israel is inappropriate, for this can be construed as belittling the honor of Maran Ha’Shulchan Aruch who was the chief authority and master of the Land of Israel.
Vessels made of pottery (ceramic, clay, china, porcelain, etc.) are unable to be koshered; even if they were to be torched with fire very well, they would remain in their forbidden state.
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.