And this is the language of the Tur: The Ittur writes that were I not afraid of other rabbis I would say that even a earthenware pot that has not been used for 24 hours since it is only a rabbinic prohibition to cook with it, can be kashered through immersion in boiling water three times and this is sufficient. And the Ittur brings proof from the Yerushalmi (Terumot 11:4). And the Rashba writes teh same thing and concludes his words by saying that perhaps this is only permissible with a rabbinic prohibition that has no basis in a Torah prohibition like Terumah or Challah outside of Israel in our times or with bishul akum (food cooked by Gentiles) but for other rabbinic prohibitions that do have a Torah basis they were strict just as with Torah prohibitions and it is appropriate to be concerns and not be lenient. All of the above is the language of the Tur. And so this leniency is entirely unmentioned in the Shulhan Arukh except for a reference in Siman 113 regarding bisul akum (food cooked by Gentiles) see there. And the Rashba in Torah haBayit discusses this at great threngh and writes that whenit comes to the strict law it appears to him that all rabbinic prohibitions should be permissible under these circumstances as the RaSh HaTzarfati writes and see there. And the Tur didn't bring the end of the Rashba's words because he was of the opinion that one should not be lenient in this way in a practical fashion. And, heaven forfend we should not violate the opinion of the Tur and Shulhan Arukh, however this is very puzzling since the Yerushalmi in Pesachim (3:1) says that when it comes to Hametz, which certainly has a foundation in Torah and the Yerushalmi there says: Rabbi Yirmiyah saidi n the name of Rav, a pot in which hametz was cooked should not be used for the same type of food until after Pesach, but a different food can be cooked in that pot even on Pesach if three items were cooked in between. And the commentator has already raised this question.
ולכן התרנו הקדרות של מתכת במדינתנו שנקראין פרייסיס"א טע"פ שהן כולו ברזל אלא שמבפנים יש איזה טיח לבן ואינו ידוע אם הוא של חרס או של עופרת כי הדבר הוא בסוד אצל הבעלי מלאכות וכל הקדרות שבמדינה בין של בשר בין של חלב הכל ממין זה ובכל יום ויום יש שנשפך משל בשר לתוך של חלב וכן להיפך כידוע והיה צער גדול והפ"מ ללבנן כי בהליבון צריך בקיאות הרבה והיה ההפסד רב שעולין בדמים יקרים והרבה נתפקעו בליבונן והתרנום להגעילם ג' פעמים אחר מעל"ע דכיון דהעיטור והרשב"א והר"ש הצרפתי דעתם נוטה להקל לגמרי אף בשל חרס גמור ורק הטור והש"ע חששו לחומרא זו דאולי הירושלמי תרומות לא התיר אלא בדבר שאין לו עיקר מן התורה ובירושלמי פסחים מבואר דבכל האיסורים מותר כמ"ש ולכן נהי דחלילה לנו לעבור על דבריהם מ"מ בספק ציפוי חרס או מתכות ועצם הקדירה הוא ודאי של מתכות פשיטא שיש להקל בדין ברור כזה ולחוס על ממונם של ישראל וקצת ראיה יש שהציפוי הוא של מתכת ולא של חרס מקרא דדניאל [ב׳ פסוק מ"ג] ולא להון דבקין דנא עם דנא הא כדי פרזלא לא יתערב עם חספא אלמא דמתכות עם חרס רחוק שיתערבו ויתדבקו ביחד ולכן הדעת נוטה שהציפוי הוא של בדיל וע׳ סי׳ קכ"ב סעי' ב' ולבד זה יש ראיה להעיטור ממה שכתבנו בסי' קי"א סעיף ג׳ ע"ש היטב:
And therefore, we have permitted metal pots in our land that are called "Freisian Pot" which are entirely iron except they place inside them some sort of white layer. And it is not known if it is made of ceramic or if it is made from some sort of metal for the matter is a secret to those who manufacture it and all of the pots in our land, whether used for meat or for dairy are all made in this way. And every day some spill some from the meat pot into the dairy pot and vice versa as is known and it was a tremendous cause of distress since it would entail great expense to kasher by means of a blow torch since that method requires great expertise and it entails great expense since hiring someone to do this requires a lot of money. And I permitted them to boil these pots three times, after waiting 24 hours. Since the Ittur and the Rashba and the Rash from France all are completely lenient even with entirely earthenware vessels and it is only the Tur and the Shulhan Arukh who are concerned and encourage strictness lest the Yerushalmi in Terumot only permits regarding a rabbinic prohibition that has no essence from the Torah. And the Yerushalmi in Pesachim explains that all prohibitions are permissible as I have written. Therefore, granted that Heaven forfend that we would violate their words, nonetheless, in a case of doubt about whether or not the enamel is earthenware or metal and the essence of the pot is certainly metal, it is obvious that one can be lenient in a clear case like this and to be concerned about the money of Israel. And a small proof that the enamel is metallic and not earthenware can be found in the Book of Daniel (2:43): "You saw iron mixed with common clay; that means: they shall intermingle with the offspring of men,-e but shall not hold together, just as iron does not mix with clay." Apparently metal and earthenware do not mix or stick together and so it is logical to assume that the enamel is made of metal. And see Yoreh Deah 122:2. And in addition there is further proof for the Ittur from what is written in 11:3 and seee there.
In practice, the poskim rule that one may perform hagala on enamel utensils like all other metal utensils, and some recommend performing hagala three times. Yet regarding Pesaḥ, some instruct not to perform hagala on enamel utensils in light of the severity of the ḥametz prohibition.
Footnote:
Responsa Ḥatam Sofer 113 states that enamel is koshered via light libun. R. Shlomo Kluger rules stringently that one may not kosher enamel even via libun, since it might get damaged in the process (Tuv Ta’am Va-da’at, first edition §183). Ktav Sofer YD 78 permits koshering enamel via triple hagala. SHT 451:191 quotes Ḥatam Sofer and then states that many great authorities were more stringent in this matter when it came to Pesaḥ. This is also the view of Maharsham 1:53. Aderet rules that one may kosher such utensils via hagala, but out of respect for Ḥatam Sofer states that one should use triple hagala (which according to Itur works even for earthenware vessels once twenty-four hours have elapsed since they were last used). This is also the opinion of AHS YD 121:27. R. Mordechai Eliyahu states that one may kosher these utensils for Pesaḥ via hagala, and preferably triple hagala