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) and in this way, it will be permissible to use it on Pesach.
Porcelain or Pottery Vessels
Nevertheless, the above only applies to plates made out of plastic or metal; however, plates made of pottery cannot be koshered for Pesach, for the Torah states that pottery can never release what it has absorbed, as the verse states, “An earthenware vessel that has been cooked shall be broken.” The same applies to ceramic, and china vessels in that they cannot be koshered for Pesach. Once, in the year 5730 (1970) when Maran zt”l was serving as the Chief Rabbi of Tel Aviv-Yaffo, Maran zt”l heard that some hall and restaurant owners wished to kosher ceramic dishes for Pesach at which point he sent them a letter stating that according to Halacha, one cannot kosher such dishes for Pesach. Maran zt”l instructed them to purchase new dishes for Pesach and only then would they receive authorization from the rabbinate to operate on Pesach. (Yalkut Yosef, Volume 3, page 399)
The Radbaz writes (Volume 3, Chapter 401) that porcelain vessels retain exactly the same law as pottery and it is therefore impossible to kosher it. Several great Poskim concur, including the Peri Chadash, Hagaon Rabbeinu Eliyahu Yisrael in his Sefer Shenei Eliyahu, and Hagaon Rabbeinu Chaim Palagi in his Sefer Mo’ed Le’Kol Chai, among others.
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 (during the rest of the year, if the frying pan absorbed actual prohibited foods, it must be torched with fire even according to the Sephardic custom) 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.
The refrigerator should be thoroughly cleaned so that not even a crumb of Chametz remains and it is then permissible to be used on Pesach without hindrance, for it has never absorbed any Chametz flavor since it is always used with cold foods.