Kashrus in the Kitchen (22). Separation of Meat and Dairy.
Kashering Keilim and Dishes (cont.). Last week we mentioned the widespread custom to refrain from kashering from dairy to meat, and vice versa. If one were to kasher one set of dishes back and forth, sooner or later he may come to a mistake by forgetting to kasher. Thus, all such kashering was avoided entirely. Kashering keilim was left for things that mistakenly became treif, or for before Pesach. We mentioned 5 exceptions where one may kasher from type to type: If he is kashering for Pesach anyways; glass utensils; utensils unused for 12 months; making it treif and then kashering and changing the type; and one who received or bought used utensils that were never used before. We continue here with more details on this important topic.
Used By Mistake. If one mistakenly kashered from one type to the other and then used it for the new type, the Maharsham (1) rules that we can allow it and he can use it for the new type.
Great Need. If one has a great need for the use of a utensil and cannot fill the need without kashering from one type to the other, the Pri Megadim (2) permits it on a one-time basis. Today, when there are so many utensils that one can buy for cheap, it would be hard to find such a case that fits this criteria.
Parve (Non-Dairy). The strict custom was not to kasher from one type to the opposite type. However, one can kasher from dairy or meat to parve. There is a psak from the Maharsham (3) that is misunderstood. He rules that if one genuinely needed to kasher from one type to parve and later wants to go from parve to the opposite type that it was before, he can designate it as such and do so. He doesn’t say that one may go from milk to meat by disguising it and “artificially” kashering it for parve, having in mind to change it to meat usage. Some contemporary seforim might have understood it differently and I don’t think it is correct.
Ovens. There seems to be one case where we may not be consistent with keeping this minhag. That is the case of kitchen ovens where people cook, sometimes dairy and sometimes meat. This is often done in ways that might need kashering in between, such as steamy uncovered items, and yet people are still lenient to kasher from one to the other. This seems to be approved by the Mishna Berura (4). It could be because (especially in the olden days) many people did not have two ovens, due to a lack of space, or expense, so they never accepted on themselves the custom on such items (5). Even though this has become a standard activity in kitchens today, some Poskim (6) feel that it should only be done once in a while, only when completely necessary, not kashering back and forth too often. Others permit it completely (7).
(1) שו"ת מהרש"ם ב:רמא (2) פמ"ג אשל אברהם או"ח תנב:יג (3) מהרש"ם שם (4) משנה ברורה תצו:טו (5) ע' פסקים ותשובות קכא:קעד (6) חלקת יעקב יו"ד כ"ג, להורות נתן א:לד (7) מנחת יצחק ה:כ:יד, אור לציון ג:י:ב