Dishwasher interiors are normally coated with porcelain, metal, or plastic. In this chapter, we discuss the feasibility of kashering diswashers whose interiors are made of these materials.
Kashering Earthenware
The Torah (Vayikra 6:21) teaches the laws concerning vessels in the Beit Hamikdash which absorbed “taste particles” of korbanot (sacrifices), and what happens when these tastes become forbidden as notar (leftovers from an expired korban).1For example, a vessel in which a korban chatat (sin offering) was cooked contains notar taste particles within its walls the morning after the korban was brought. Since it absorbed the taste particles from the korban, the same laws apply to the particles as would apply to an actual offering. Thus, when the korban becomes notar, the vessel also becomes forbidden. The vessel may not be used until the taste particles have been purged from it. The Torah teaches that metal utensils may have their notar taste particles purged by being placed in boiling hot water and subsequently being rinsed in cold water. Outside of the Temple, the rinsing is not necessary, although it is done anyway as a reminder of the customs that were performed in the Temple (see Tosafot, Avodah Zarah 76b s.v. Mikan, and Aruch Hashulchan, Orach Chaim 452:20). The Torah states that earthenware vessels that were used to cook korbanot must be destroyed. The Gemara (Pesachim 30b) states, based on this verse, that the flavor absorbed by an earthenware vessel can never be completely purged. Thus we see that metal can be kashered while earthenware generally cannot. The only way to kasher earthenware is by running it through a kiln (see Shulchan Aruch, Orach Chaim 451:1). Rabbeinu Tam (Tosafot, Pesachim 30b s.v. Hatorah) explains that a kiln does not purge the taste particles, but it recreates the utensil into a new object (cheftza), which has never been used to cook a korban.2I heard Rav Moshe Tendler state that a self-cleaning oven can function as a kiln in this respect. According to Rav Tendler, a non-kosher earthenware dish may be kashered by staying inside an oven for an entire self-cleaning cycle (assuming that the intense heat does not break or damage the dish). Obviously this kashering procedure cannot be used to kasher a dishwasher, since there is no practical way to put a dishwasher into a kiln without destroying the dishwasher. I have heard that Rav Yosef Weiss disagrees with this ruling, arguing that a self-cleaning oven will only subject the dish to intense heat but not actual fire. See Teshuvot Avnei Neizer (Yoreh Deah 110) for a discussion whether libun works because of fire touching the dishes or because of the dishes being subjected to intense heat.
The Status of Porcelain
Of the many types of earthenware, porcelain specifically is often used to coat dishwashers. Porcelain is essentially non-porous earthenware and therefore does not absorb in the same manner as regular earthenware. Consequently, Acharonim debate whether it absorbs anything from non-kosher food or not, due to its non-porous nature, and, assuming it does absorb, whether it can be kashered. The Darchei Teshuvah (121:26) cites numerous opinions regarding porcelain, ranging from those who believe that porcelain requires no kashering whatsoever (She’eilat Yaavetz 1:67) to those who believe that it may never be kashered. The Mishnah Berurah (451:163) rules strictly, that porcelain shares the same status as other earthenware, which may not be kashered at all. Rav Eliezer Waldenberg (Teshuvot Tzitz Eliezer 4:6) summarizes this issue:
Much ink [has been] spilled in attempting to rule that since porcelain is non-porous it need not be kashered. Nevertheless, the consensus of halachic opinions, along with the accepted 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 Darchei Teshuvah cites those who factor in the lenient opinions on this issue when rendering decisions in already questionable cases, as an added reason to be lenient (senif lehakeil). As an example of such a case, Rav Moshe Feinstein (Teshuvot Igrot Moshe, Yoreh Deah 3:28-29) rules that if one purchases a home containing a non-kosher porcelain dishwasher, the dishwasher may be kashered. He reasons that not kashering the dishwasher would incur a significant monetary loss, leading to a situation in which the above leniencies may be used (also see Teshuvot Yabia Omer, Y.D. 1:6). However, he rules that it may be kashered only after it has not been used for a full year, and it must be fully kashered three times.
Rav Moshe combines three unrelated lenient minority opinions in this ruling. As mentioned above, some authorities permit kashering porcelain because of its non-absorbent nature. Additionally, Rav Moshe factors in the Baal Ha’itur’s view (cited by the Tur, Yoreh Deah 121) that although an earthenware vessel cannot be kashered in the conventional way, in certain situations it may be kashered by performing the kashering process three times. Although this represents only a minority view, halachic authorities occasionally cite it as an added consideration in their lenient rulings in case of great need.3See for example Aruch Hashulchan (Yoreh Deah 121:26-27) and Teshuvot Melamed Leho’il (2:52). As a third lenient consideration, Rav Moshe quotes a celebrated opinion of the Chacham Tzvi (75, cited by the Shaarei Teshuvah 451:1). The Chacham Tzvi believes that after twelve months, the absorbed non-kosher flavor becomes “mere dust,” with no halachic status as a prohibited food.4The Chacham Tzvi bases his position on Talmud’s assertion that vessels that have absorbed non-kosher wine lose their non-kosher status after twelve months (Avodah Zarah 34a). He applies this statement regarding wine to other areas of kashrut, too. In practice, the Chacham Tzvi writes that one should follow his lenient ruling only in b’dieved (post facto) situations, where something was already cooked after the pot had not been used for twelve months. Hence, while after twenty-four hours an absorbed taste becomes rancid (noten ta’am lifgam; see Avodah Zarah 75b-76a) and is only rabbinically forbidden, after twelve months the flavor disappears completely.
Reactions among halachic authorities to the Chacham Tzvi’s ruling have been mixed. The Aruch Hashulchan (Yoreh Deah 122:4) rejects this leniency entirely, while the Chochmat Adam (55:4) appears to accept it. Adopting a middle approach, the Sha’arei Teshuvah (ibid.) rules that the Chacham Tzvi’s leniency may be used only as one lenient consideration, in combination with the Ba’al Ha’itur, if there is also a third lenient consideration.
Rav Moshe apparently follows the approach of the Sha’arei Teshuvah, combining three lenient approaches: those of the Ba’al Ha’itur and the Chacham Tzvi, along with that of Rav Yaakov Emden (She’eilat Ya’avetz 1:67), who maintains that porcelain does not require kashering.5See Teshuvot Melamed Leho’il (2:52), who combines a somewhat similar list of minority opinions to permit kashering earthenware dishes in a complex and problematic situation. Rav Moshe therefore permits, in case of significant monetary loss, to kasher non-kosher porcelain dishwashers for the rest of the year, provided that the kashering is done three times after the appliance has not been used for an entire year.6In cases of great need, Rav Moshe does not require waiting a year. On the other hand, Rav Yosef Adler reports that Rav Yosef Dov Soloveitchik does not subscribe to Rav Moshe’s leniency. Rather, Rav Soloveitchik maintains that porcelain dishwashers may never be kashered.
It is vitally important to note that Rav Moshe does not apply his ruling to Pesach use. In a separate responsum, he rules that porcelain dishwashers may not be kashered for Pesach use under any circumstances (Teshuvot Igrot Moshe, Orach Chaim 3:58). His position conforms to the general trend of treating the prohibition against chametz on Pesach more strictly than the laws of kashrut for the rest of the year (chumra d’chametz). Just as we do not apply the leniencies of nullification by a 60:1 ratio (bitul beshishim) and (according to Ashkenazic practice) notein taam lifgam on Pesach,7See Shulchan Aruch, O.C. 447:1 and 447:10. so, too, Rav Moshe does not apply his lenient view regarding dishwashers to Pesach.8See Rav Moshe’s view as quoted in Rav Shimon Eider’s Halachos of Pesach p.138 note 15.
Metal-Lined Dishwashers
In his aforementioned responsum, Rav Moshe rules that a metal-lined dishwasher may be kashered provided that it is first cleaned thoroughly. Several classical sources highlight the necessity of properly cleaning a utensil before kashering.9See Rabbeinu Tam’s explanation of Pesachim 30b (cited in Tosafot, Chulin 111b-112a s.v. Hilch’ta), Shulchan Aruch (Orach Chaim 451:3), Rama (Orach Chaim 451:18) and Mishnah Berurah (451:56,156). Indeed, the Mishnah Berurah (451:156) writes, “Any utensil that one cannot extend his hand into [in order to thoroughly clean it] may not be kashered.”
While Rav Moshe does permit the kashering of those dishwashers that can be thoroughly cleaned, some rabbis object to kashering all dishwashers for Pesach due to the concern that they can never truly be cleaned thoroughly. A dishwasher’s many nooks and crannies generate this concern, and these rabbis worry that the many holes and crevices within the dishwasher make cleaning it thoroughly nearly impossible.10Some authorities raise similar objections to kashering microwave ovens, as we discuss in the next chapter. Rav Moshe apparently does not share that concern either, as he permits kashering a microwave for Pesach (quoted by Rav Shimon Eider, Halachos of Pesach, p. 182).
Nonetheless, some authorities do permit kashering metal dishwashers, but it is not entirely clear how to do so. The Torah articulates the basic guidelines of kashering in Bemidbar (31:23), “That which became not kosher through contact with fire must be kashered with fire, and that which became not kosher in a water medium, must be kashered in a water medium.” This verse establishes the principle that an item must be kashered in the same manner as its use. Dishwashers come in contact with food particles through hot water, so they should be kashered with hot water (hag’alah). Rav Moshe writes that when kashering a dishwasher, a hot brick must be placed inside the dishwasher to boost its water’s temperature to the boiling point,11Dr. Joel Berman notes that, scientifically speaking, it is difficult to imagine how this brick would raise the water to the boiling point. The brick would not access all of the water, and the brick’s outside temperature would rapidly fall as the water cooled it down. based on the practice of using boiling water whenever water is required (see Taz, Yoreh Deah 94:3 and Mishnah Berurah 452:8). Hence, even though the water’s temperature never climbs higher than 190 F in dishwashers,12In a lecture at Yeshiva University in 1989, Rav Moshe Tendler reported that at that time the water did not get hotter than 190tF. kashering them still requires boiling water.
On the other hand, Rav Mordechai Willig (SOY Guide to Kashrut p. 66) and Rav Yosef Adler (personal communication) quote Rav Soloveitchik’s view that if one is absolutely certain of the maximum temperature that the water reaches when the dishwasher absorbs non-kosher (or chametz) taste, then it may be kashered at that temperature. Rav Soloveitchik requires boiling water only when one is unsure of the maximum temperature to which the appliance has been exposed. Since one knows the maximum temperature that the dishwasher has reached, it may be kashered (after being left unused for at least twenty-four hours) simply by running it through a full wash cycle. In such a manner, the water in the machine is the hottest to which the appliance has ever been exposed and will thus purge the non-kosher flavor. The Mishnah Berurah (Shaar Hatziyun 451:196) seems to agree with Rav Soloveitchik’s contention by suggesting that most authorities understand the rule of kevol’o kach polto as meaning that each utensil is kashered with water that is as hot as the water that it uses (see our earlier chapter regarding kashering ovens).
Plastic Lined Dishwashers
Many dishwashers today are lined with plastic. The ability to kasher them depends on how to categorize materials (such as plastic) that did not exist in the time of the Talmud. Rav Moshe (Teshuvot Igrot Moshe, Orach Chaim 2:92) writes that one may not kasher synthetic rubber “since it is new and unaddressed in the classical sources.” The same would seemingly apply to plastic. Interestingly, though, it seems that Rav Moshe ruled this strictly only concerning Pesach, as Rav Shimon Eider (Halachos of Pesach p. 138 note 10) writes that Rav Moshe does permit kashering plastic during the rest of the year. Apparently, he considers this area to be another example of the chumra d’chametz (special Pesach stringencies).
Many contemporary authorities do not share Rav Moshe’s objection to kashering synthetic materials. Rav Eider (Halachos of Pesach p. 138 note 10) cites that Rav Yosef Eliyahu Henkin went so far as to rule that plastic does not require kashering at all, because it is smooth and does not absorb (shi’a velo bal’i). Although Rav Henkin’s view is a minority opinion,13Mr. Phillip Berman (of Springfield, Massachusetts) informed me that, in fact, most forms of plastic do indeed absorb. Mr. Berman worked for many years as a senior research plastics scientist at the Monsanto Corporation. many contemporary authorities who assume that plastic does absorb non-kosher flavor nevertheless permit kashering it, even for Pesach. Rav Eliezer Waldenberg (Teshuvot Tzitz Eliezer 4:6) and Rav Ovadia Yosef (Chazon Ovadia vol. 2 [Hagaddah Shel Pesach] p. 78) permit the kashering of plastic utensils for Pesach, as does Rav Gedalia Felder (Yesodei Yeshurun 6:170-173) in case of great need.14Rav Yaakov Breisch (Teshuvot Chelkat Yaakov 2:163) also permits the kashering of plastic (and does not distinguish between Pesach and non-Pesach use), as does Rav Yitzchak Yaakov Weisz (Teshuvot Minchat Yitzchak 3:67) under some limited circumstances. The Maharsham (3:233) also appears to permit the kashering of synthetic materials. According to these authorities, a utensil may be kashered as long as it does not contain earthenware. Indeed, Rav Yechiel Yaakov Weinberg (Teshuvot Seridei Eish 1:46) writes that the accepted practice is to kasher plastic, without limiting his ruling to non-Pesach use.
Conclusion
Each of the three types of dishwashers presents its own challenges in terms of kashering for Pesach. In addition, many of the relevant facts, such as the heat of a dishwashing cycle, are subject to change in light of technological developments. One should consult a competent rabbi regarding which approaches to follow.