The Shulchan Aruch (Orach Chaim 429:1) records the celebrated Talmudic dictum (Pesachim 6a) that one begins studying the laws of Pesach thirty days before Pesach. The Mishna Berura (429:1) cites opinions that this rule applies exclusively to Pesach, since the laws of Pesach are so detailed and complex. Among the complexities, notes the Mishna Berura, are the laws of kashering for Pesach. In addition, Rav Soloveitchik observes that Shabbat Hagadol usually falls out on Parshat Tzav. The Rav suggested that this is because Parshat Tzav contains many of the Halachot of kashering. Accordingly, we have chosen to discuss this week a very relevant issue, the kashering of a dishwasher for Pesach.
Dishwasher interiors are, generally speaking, coated with porcelain, metal, or plastic. Therefore, we will discuss the feasibility of kashering utensils made of these materials. The Torah in this week's Parsha teaches (Vayikra 9:21) laws concerning vessels in the Beit Hamikdash which absorbed "taste particles" () of the Korbanot, which become forbidden as Notar (leftovers), after the time the particular Korban may be eaten has elapsed. For example, the morning after a vessel in which a Korban Chatat was cooked contains Notar taste particles within its walls, since the vessel absorbed taste particles from the Korban Chatat that was cooked within it. Just as the Korban Chatat becomes Notar the morning after it is offered, the absorbed food particles from the Korban become Notar the morning after the Korban is offered.
The Torah teaches that we may not use vessels that have Notar taste particles within them, until these particles have been purged from the vessel. The Torah teaches that metal utensils may have their Notar taste particles purged by being placed into boiling hot water and subsequently rinsed in cold water. Outside of the Temple we are not required to rinse a utensil in cold water after it is purged. Our practice is to do so as a reminder of our procedures in the Beit Hamikdash (see Tosafot Avoda Zara 7b s.v. and Aruch Hashulchan 452:20).
This Pasuk, however, also teaches that earthenware vessels in which Korbanot were cooked must be destroyed. Rashi quotes the Gemara (Pesachim 30b) which derives from this Pasuk that , an earthenware vessel can never have all of its absorbed taste particles purged. Thus, we see that metal vessels can be kashered but earthenware cannot be kashered. However, even earthenware may be kashered by returning it to a kiln, (see Shulchan Aruch O.C. 451:1). Rabbeinu Tam explains this exception (Tosafot Pesachim 30b s.v. ) by stating that a kiln does not purge the taste particles from the earthenware; instead, it recreates the utensil. When the utensil emerges from the kiln it is considered a new vessel. Rav Hershel Schachter informed this author of Rav Soloveichik's ruling that a self-cleaning oven can act as a kiln in this regard. Accordingly, a non-kosher earthenware vessel may be kashered by running through a cycle in a self-cleaning oven (if the vessel doesn't break due to the heat!) This procedure, obviously, is not relevant to our question of kashering a dishwasher.
The Status of Porcelain
The question we are faced with is whether porcelain may be kashered or not. Porcelain, simply put, is non-porous earthenware. Acharonim debate whether it may be kashered or perhaps need not be kashered at all since it is non-porous. The Darkei Teshuva (121:26) cites various opinions on this issue. The Mishna Berura (451:163) rules strictly, that porcelain has the status of earthenware and cannot be kashered. Rav Eliezer Waldenburg summarizes the issue:
Look at all the ink spilled in a attempt to rule that since porcelain is non-porous it need not be kashered. Nevertheless, the consensus of Halachic opinion and the accepted Halachic practice is to treat porcelain as earthenware which may not be kashered.
Accordingly, it would seem that a porcelain coated dishwasher cannot be kashered. However, the Darkei Teshuva cites opinions that rule that the lenient opinions regarding porcelain may be used, in case of great loss, as a , a lenient factor that a rav may consider when rendering a decision in a specific case.
Rabbi Feinstein - Lenient Ruling
In fact, Rav Moshe Feinstein (Igrot Moshe Yoreh Deah 3:29) rules that if one purchases a home containing a non-kosher dishwasher, the dishwasher may be kashered, due to a significant loss. However, he rules that it may be kashered only after the dishwasher has not been used for at least a year, and it must be kashered three times.
The Three Combined Leniencies
Rav Moshe combined three lenient rulings in his decision regarding porcelain dishwashers. The first lenient ruling is the aforementioned opinions which regard porcelain as non-absorbent. The second is the celebrated opinion of the Baal Haitur. The Tur (Yoreh Deah 121) cites the Baal Haitur's extraordinary lenient ruling that although an earthenware vessel cannot be kashered in the conventional way, it can be kashered if the procedure is performed three times. Although this represents only a minority view, Halachic authorities use the Baal Haitur's ruling as a (see for example Aruch Hashulchan 121:26-27 and Rav David Zvi Hoffman's Teshuvot Melamed Lehoil 2:52).
The third leniency is a celebrated responsum of the Teshuvot Chacham Zvi (number 75) cited by the Shaarei Teshuva (451:1). This authority believes that the Talmud's teaching that vessels that have absorbed non-kosher wine lose their status as non-kosher twelve months subsequent to the removal of the non-kosher wine from the vessel ( " ) would apply to other areas of Kashrut as well. He believes that after twenty-four hours an absorbed taste becomes , gives off a rancid taste (see Avoda Zara 75b-76a) and is significant on a Rabbinic level. However, the Chacham Zvi argues, after twelve months the absorbed taste particles have become "mere dust" and thus have no Halachic significance (they are beyond ; they are mere dust).
Reactions among Halachic authorities to the ruling of the Chacham Zvi are mixed. On one hand, the Aruch Hashulchan (Y.D. 122:4) rejects this leniency entirely. On the other hand, the Chochmat Adam (55:4) seems to accept this leniency wholeheartedly and with regard to all areas of Kashrut. A middle approach is that of the Shaarei Teshuva, who rules that the Chacham Zvi's leniency may be combined with the Baal Haitur's leniency and one other lenient consideration.
Rav Moshe appears to have followed the approach of the Shaarei Teshuva combining three lenient approaches: those of the Baal Haitur and the Chacham Zvi, and that of Rav Yaakov Emden, (Sheilat Yaavetz 1:67) who regards porcelain as not requiring kashering.
The Pesach Stringency
It is vitally important to note that Rav Moshe did not rule this way regarding kashering a porcelain dishwasher for Pesach. In a responsum addressed to Rabbi David Stavsky of Columbus, Ohio (Igrot Moshe Orach Chaim III:58) Rav Moshe rules that porcelain dishwashers may not be kashered for Pesach under any circumstances. This is characteristic of Hilchot Pesach - we are much more stringent than during the rest of the year. Just as the leniencies of (nullification by sixty times more kosher food than non-kosher food) and do not apply on Pesach, so too Rav Moshe did not apply his leniency regarding porcelain dishwashers to Pesach kashering (see Rav Moshe's view quoted in Rabbi Eider's Halachot of Pesach p.138 note 15).
Porcelain dishwashers may under no circumstance be kashered for Pesach. Rav Moshe Feinstein ruled leniently in case of significant monetary loss, to allow a non-kosher porcelain dishwasher to be kashered for non-Pesach use, if kashering is done three times after not having been used for one year. It should be noted that Rav Yosef Adler reports that Rav Soloveitchik does not subscribe to Rav Moshe's leniency regarding kashering porcelain dishwashers for non-Pesach use. The Rav rules that porcelain dishwashers may not be kashered regardless of the monetary loss involved.