The Paradox of Purging Plastic Products
One of the remarkable debates of contemporary times concerns whether or not “new age polymers” such as plastic or Teflon can be kashered. Not simply a theoretical question, with the abundance of Tupperware and Rubbermaid products (for storing hot soups etc.), as well as plastic parts and handles and Teflon coating as part and parcel of many of our ubiquitous pots and pans, this halachic classification issue affects us all. Quite interestingly, this is an issue that authorities in America seemingly rule more stringently than many Poskei Eretz Yisrael. Additionally, there might also be a distinction between kashering from non-kosher to kosher and from chometz to kosher L’Pesach. But to properly understand these nuances, a bit of background is in order.
The Biblical source for requiring the kosherization of used pots from a non-Jew is in Parshas Mattos (Bamidbar Ch. 31: 21 - 23) after the War with Midian, when Klal Yisrael was commanded to kasher their spoils of war that were used for food preparation. “This is the rule that Hashem commanded Moshe: As far as the gold, silver, copper, iron, tin and lead are concerned, whatever was used over fire must be made to go through fire and purged…”
The principle underlying the methodology of kashering is found in the phrase, 'whatever was used over fire must be made to go through fire...'; that is to say, the manner in which a utensil was being used when the forbidden food entered it determines how it will be kashered: Utensils which came into direct contact with fire are kashered by direct contact with fire; utensils which were placed on the fire with liquids in them are kashered by boiling liquid.
Yet, we see that the only materials that the Torah actually explicitly mentioned as kasherable are six types of metals. In fact, regarding the Korban Chataas, the Torah states (Vayikra, Parshas Tzav 6: 21) that earthen vessels in which it was boiled must be broken, as opposed to a metal vessel which can be kashered.
According to the Gemara, what is clear is that the Torah meant to exclude these ‘klei cheres’, ceramic or earthenware vessels, the other prevalent types of utensils available, that they cannot be kashered. Although they do absorb, and as opposed to metal utensils, the act of purging will not actually remove the bleeyos, absorbed taste, imparted into the walls of a ‘kli cheres’.
The question then arises, what would be the status of vessels made from materials not mentioned in the Torah? Would they be classified as metals and thereby deemed kasherable or like earthen vessels which cannot be kashered?
We may glean an answer from several precedents of Chazal. We find that the Gemara in Pesachim (30b; statement of Rav Huna brei d’Rav Yehoshua) clearly states that wood can be kashered. Similarly, in Chullin (25b; statement of Rav Nachman) albeit regarding the halachos of ‘Mekabel Tumah’, that a vessel made of bone is akin to one of metal. Many Rishonim cite the above examples among others, and rule that both are indeed kasherable. They further advance the logic that a stone utensil as well shares similar status as metal and therefore may be koshered as well.
Smooth As Glass ?
The one exception to the rule is glass. Glass’s status is a major debate among the Rishonim with no clear cut consensus. The reason for this disagreement is based on how they view glass. Is it considered a sort of earthenware as it is essentially made from sand heated to extreme temperatures? Or do we look at the final product, which is smooth and non-absorbent? Perhaps its status is somewhere in the middle?
The Shulchan Aruch rules that glass is ‘shiya’, smooth, and thereby non-absorbent; therefore, he rules that it does not need to be kashered, even for Pesach. This is the general Sefardic minhag, as well. However, the Rema argues that glass is considered akin to a Kli Cheres regarding Pesach use, and therefore it cannot be kashered. He adds that this is indeed the Ashkenazic minhag - to consider glass akin to ceramic and thus non-kasherable.
With these varying halachos as precedent, how do contemporary authorities view plastic utensils? As with many issues in halachah, plastic’s kasherability status is debated.
Several contemporary authorities maintain that plastic is non-kasherable. They explain that since it is essentially a new material, it is impossible to determine if haga’alah will actually work to purge bleeyos; therefore one may not kasher plastic. Some add that since plastic is more fragile than a metal utensil, we are worried that it will not be kashered properly, and therefore advise caution. Additionally, some maintain that since plastic et al. was not around in the times of Chazal, we must be stringent regarding its kasherability.
However, in stark contrast to this, many contemporary decisors make the exact opposite deduction. They explain that Chazal singled out Klei Cheres as the one material that cannot be kashered. Therefore, all other materials, as long as they do not contain elements of Klei Cheres, should be able to be kashered. Additionally, they cite precedent from ‘Klei Adamah’ (vessels made from earth; i.e. bricks that were made and dried in the sun as opposed to a kiln) as although non-mentioned by Chazal or even Rishonim, nevertheless many poskim maintain is kasherable, and has the status of stone utensils. This should equally apply to plastic, as it is essentially petroleum and coal based and not related to ceramics.
Moreover, plasticware is generally not used directly on the fire, but rather only via pouring or the secondary transmission of Kli Sheini; if so, it by and large never had real deal absorption of bleeyos to be stringent regarding its kashering. Therefore, the vast majority of contemporary authorities maintain that plastic is indeed kasherable. Indeed, in their annual Madrich HaKashrus, the Badatz Eidah Chareidis of Yerushalayim follows the ruling of their Av Beis Din, the Minchas Yitzchok, that plastic is indeed kasherable, and even for Pesach use (as long as it did not absorb bleeyos of chometz directly on the fire). This is also the conclusion of many sefarim written on the topic of kashering.
A third approach is that although plastic may indeed be kasherable, and one may do so year-round, nevertheless, regarding Pesach with all of its inherent stringencies, it is preferable not to kasher it.
The question remains that if most contemporary poskim allow kashering plastic, why would American rabbis be more stringent than their counterparts in Eretz Yisrael? The answer lies in a responsum of the gadol hador, Rav Moshe Feinstein zt”l. In his Shu”t Igros Moshe (Orach Chaim vol. 2: 92 s.v. uvadavar kli) while discussing the kasherability of rubber, Rav Moshe seemingly sets a far-reaching rule: although natural rubber is harvested mainly in the form of the latex, a sticky, milky colloid from certain trees, and is therefore analogous to wooden utensils and thus kasherable, on the other hand synthetic rubber that is derived from petrochemical sources, ‘which is a new item that was not extant among early authorities,‘ain lehatir l’hagilam, we do not allow them to be kashered’.
It is this principle, seemingly set by Rav Moshe, which is the reason why there is general notion that plasticware may not be kashered. In fact, this is cited by many as the reason to be stringent that plastic, and de facto any ‘New Age’ product, may not be kashered.
However, and although it may come as a surprise to many, and especially to those who quoted Rav Moshe this way, history has since proven that this was not his true shitta. First of all, several of Rav Moshe’s leading talmidim, including the Yesodei Yeshurun, Rav Shimon Eider, and Rav Avrohom Blumenkrantz, in their sefarim pertaining to kashering, make no mention of their Rebbi being machmir regarding kashering plastic year-round. In fact, Rav Eider writes that Rav Moshe told him that he personally was only machmir regarding kashering plasticware for Pesach. However, regarding basar bechalav and year-round use, he held that plastic may be kashered. Indeed, in his recent Mesores Moshe, Rav Moshe’s grandson, Rav Mordechai Tendler relates that Rav Moshe told him that his rule was only applicable regarding kashering for Pesach.
This further bears out from the actual stringent teshuva itself, which is dated the 6th of Nissan, right before Pesach, and is published in his responsa on Orach Chaim, where the halachos of kashering for Pesach are detailed and not in a section on Yoreh Deah, where year round kashering is discussed.
But the real clincher is that Rav Moshe actually later wrote a specific teshuva explicitly stating this. However, since his ruling was actually an addendum to a much larger teshuva on a completely separate and complicated issue, many did not realize it even exists. In Shu”t Igros Moshe (Even Ha’ezer vol. 4: end 7 s.v. uv’inyan) Rav Moshe writes regarding ‘vessels made from Teflon (and) plastic, haga’alah works to kasher them after 24 hours, as it is a safek derabbanan.’ In other words, regarding year-round use, as long as it is 24 hours after the last use, and the bleeyah is pagum (rendered unfit for consumption), and thus the kashering is only Rabbinically mandated, kashering does indeed work on plastic and Teflon. This proves that his stringent ‘New Age product rule’ was only meant to be applicable pertaining to purging plastic for Pesach.
Postscript: AlthoughRav Moshe’s son, Rav Dovid Feinstein, was quoted as only allowing kashering plastic for year round use b’shaas hadchak, this author asked Rav Baruch Moskowitz, Rav Dovid’s talmid muvhak and author of Shu”t Vedibarta Bam, to clarify his Rebbi’s and his father’s shitta. Rav Dovid replied that undeniably, as his father detailed in his second teshuva, plastic is indeed kasherable. However, since this kashering is permitted m’toras safek sfeika and not m’toras vaday, as plastic was not in existence at the times of Chazal, therefore one should only kasher plastic ‘le’ais hatzorech’, at a time of personal need. In other words, one should not rely on kashering plastic lechatchilla, i.e. purchasing used plastic products from a non-Jew and then kashering them, but if someone had a kashrus sheilah on his plastic product, he need not throw it out, but may indeed kasher it.
Note: This article is not intended to serve as an exhaustive guide, but rather to showcase certain aspects of the intricate and myriad halachos of kashering keilim. One should be sure to ask a knowledgeable halachic authority for practical application.
This article was written L'iluy Nishmas the Rosh Yeshiva Rav Chonoh Menachem Mendel ben Yechezkel Shraga, R’ Chaim Baruch Yehuda ben Dovid Tzvi, L’Refuah Sheleimah for R’ Shlomo Yoel ben Chaya Leah, Henna Rasha bas Yitta Ratza and Rochel Miriam bas Dreiza Liba, and Shira Yaffa bas Rochel Miriam v’chol yotzei chalatzeha for a yeshua sheleimah teikif u’miyad!
For any questions, comments or for the full Mareh Mekomos / sources, please email the author: firstname.lastname@example.org.
Rabbi Yehuda Spitz serves as the Sho’el U' Meishiv and Rosh Chabura of the Ohr Lagolah Halacha Kollel at Yeshivas Ohr Somayach in Yerushalayim.
 Plastic was first invented in 1907 by chemist Leo Baekeland (and dubbed Bakelite), whereas Teflon was actually accidentally discovered in 1938 by chemist Roy Plunkett, while working for DuPont.
 Mishnah and accompanying Gemara (Avodah Zarah 75b). This paragraph was paraphrased from the introduction to the English version of Rabbi Tzvi Cohen’s “Tevillath Keilim”. This halachic rule is known as ‘k’bolo kach polto’, meaning the method by which it absorbed (cooked in) the taste or flavor of the non-kosher food determines the process needed to purge the utensil of it, and thus rendering the utensil fit for kosher use.
 According to the Abudraham (pg. 372), and cited lemaaseh by the Levush (Orach Chaim 428: 4) and Elyah Rabbah (ad loc. 5), the reason why Parshas Tzav generally falls out on Shabbos Hagadol, the Shabbos immediately preceding Pesach, is that it mentions the halachos of Kashering Keilim (Vayikra, Ch. 6: 21), albeit regarding the Korban Chata’as, as ‘haga’alas keilim chometz lamud m’Korbanos’. Although in a leap year Parshas Metzorah is usually read directly before Pesach, it is also in sync, as it mentions ‘kli cheres yishaver’, which is quite apropos for Pesach as well.
 See Beis Yosef (Yoreh Deah 122: 8 s.v. kasav) who writes a general rule that standard vessels mentioned without any distinguishing characteristics, are ceramic.
 Gemara Pesachim (30b) and Avodah Zarah (34a), and codified by the Shulchan Aruch (Orach Chaim 451: 22). However, Rabbeinu Yoel, cited by the Tur and Shulchan Aruch (ad loc. 21) maintains that if a ceramic vessel was only used for cold, then it can actually be kashered for Pesach via haga’alah. See Biur HaGr”a (ad loc. 22 s.v. aval).
 For example, the Rambam (Hilchos Chometz U’Matzah Ch. 5: 25) explicitly rules that stone has the same halachic properties as metal for this issue. The Ravya (Pesachim 464 s.v. v’kaaros and v’raisi) rules the same regarding wood and stone vessels. The Rif (Pesachim 8b in his pages), Rosh (Pesachim Ch 2: 7), Mordechai (Pesachim 553), and Tur (Orach Chaim 451: end 8) all rule this way as well, as do the Ramban, Rashba, and Ritva, in their commentaries to Pesachim ad loc. The Beis Yosef (ad loc. s.v. ain chiluk) concludes ‘v’chein nahagu olam’.
 For example, regarding vessels made from bone and ‘keren’, the Mahari Weil (Shu”t 193), the Sefer Hamanhig (Hilchos Pesach 30; cited by the Tur, Orach Chaim 451: 7), and Maharil (Hilchos Haga’alah 14; pg. 23) exhort caution, as they were worried that due to its more delicate nature, one may not actually kasher it properly. Although the Kol Bo (48; pg. 9, 4th column) cites this opinion, he adds that many disagree with this assessment. On the other hand, the Bach (Orach Chaim 451: 9 s.v. mah shekasav and v’Rav) concludes that ‘divrei Baal Hamanhig ha’ikar, v’hachi nahug’. Quite contrary to this, Rabbeinu Yechiel of Paris (Psakim 84; cited approvingly by the Ohr Zarua, Piskei Avodah Zarah 297; and by the Mordechai, Pesachim 582 - who however argues) holds that bone is entirely non-absorbent and therefore does not need kashering. Rashi (Shu”t Rashi 76) however concludes that bone is indeed kasherable. Regarding stone, several early authorities have differing opinions. For example Rav Hai Gaon (Otzar HaGaonim, Pesachim pg. 28; cited by the Tur, Orach Chaim 451: 8) is of the opinion that stone should be akin to klei cheres and thereby non-kasherable. At the other extreme is the Ri ben Malki Tzedek (Maseches Keilim Ch. 10: 1) [cited by the Ravya (Pesachim 464 s.v. v’raisi),andthe Ran (Pesachim 8b in the Rif’s pages s.v. nakut); his shittah is based on a Tosefta in Zavachim (Ch. 10: 6)], that stone does not absorb taam at all. However, it should be noted that others (see Ravya, ibid; Ohr Haganuz on the Tosefta ad loc. 6; and Minchas Bikurim ad loc. s.v. ela), including the version generally printed in our Gemaros, have a different girsa in the Tosefta, implying that ‘klei even’ and ‘klei adamah’ can and must be kashered and only klei cheres need to be broken.
 See Shulchan Aruch and Rema (Orach Chaim 451: 8), citing several of the aforementioned Rishonim, including the Rif, Rambam, Rosh, and Mordechai. See also Levush (ad loc. 7; although the haghah adds that there are those who are stringent with boneware), Shach (Yoreh Deah 99: 3), Taz (ad loc. 1), Magen Avrohom (Orach Chaim 451: 4) Pri Megadim (ad loc.Mishbetzos Zahav 31 s.v. klei etzem), Shulchan Aruch Harav (Orach Chaim 451: 25), Chayei Adam (vol. 2: 125, 3),Kitzur Shulchan Aruch (116, 2), Aruch Hashulchan (Orach Chaim 451: 8 and 20), and Mishnah Berurah (ad loc. 57; however, similar to the Levush and Pri Megadim, he rules against kashering utensils made of ‘keren’ due to their delicate nature, based on the Sefer Hamanhig cited above) who all list these materials, including bone, as completely kasherable. However, the Yad Yehuda (Yoreh Deah 69, Pirush Ha’aruch end 81 and Pirush Hakatzer 117) and the Darchei Teshuva (Yoreh Deah 121: 25) distinguish between utensils made out of whole stones and those formed from crushed or ground up stone; in the latter case, they rule that lidivrei hakol they cannot be kashered as they are comparable in both makeup and process to ‘klei cheres’.
 There are three essential opposing shittos of the Rishonim on how to view glassware: Rabbeinu Yechiel of Paris’ opinion (cited by Haghos Maimoniyos, Hilchos Chametz U’Matzah Ch. 5: 25 and the Mordechai, Pesachim 574) that since glass is formed from sand it has the status of a kli cheres and cannot be kashered. This is also the opinion of the SMa”G (Lavin 78), SMa”K (Mitzvah 222), Agur (736), Terumas Hadeshen (vol. 1: 132 and vol. 2: 152), and Issur Vehetter (58: 50; he maintains that we take on the chumros of both cheres and metal and therefore both kashering and tevillah are required for glassware). However, the majority opinion is that glass is ‘shiya’, smooth, and is non-absorbent; therefore no kashering is required. This is the opinion of Rabbeinu Tam (Tosafos inAvodah Zara 33b s.v. konya and Kesuvos 107b s.v hani), the Ran (Pesachim 9a in the Rif’s pages s.v ki), Rashba (Shu”t vol. 1: 233), Rosh (Pesachim Ch. 2: 8), Rabbeinu Yerucham (Nesiv 5, vol. 2, pg. 40a), and Ravya (Pesachim 464); as the Beis Yosef concludes (Orach Chaim, end 451), ‘v’chein anu nohagin’. There is also a third minority opinion, that of the Rambam in his Pirush Hamishnayos (Avodah Zarah Ch. 5: 12 s.v. halokeyach) and Ra’ah (cited by the Ritva, Pesachim 30b s.v. li’avad; the Shibolei Haleket, Seder Pesach 207, implies this way as well) is that glass is akin to metal, that it can absorb and is kasherable. However, the Ra’ah and Ritva conclude that even so, one may not rely on this, as due to its delicate nature one may not actually kasher the glassware properly.
 Shulchan Aruch (Orach Chaim 451: 26), Beis Yosef (ad loc.), Pri Chodosh (ad loc. 26), Haghos Mahar”A Azulei (on Levush ad. loc), Shu”t Yabea Omer (vol. 3 Yoreh Deah 11: 5 and vol. 4 Orach Chaim 41), Shu”t Yechaveh Daas (vol. 1: 6), Shu”t Ohr L’Tziyon (vol. 3: Ch. 10: 12), Chazon Ovadia (Hilchos Pesach pg. 78), and Yalkut Yosef (Kitzur Shulchan Aruch 451: 39). However, there are several Sefardic poskim including the Ben Ish Chai (Year 1, Parshas Tzav 14 and Shu”t Rav Pe’alim vol. 3 Orach Chaim 29) and his followers (see Rav Mordechai Eliyahu’s Darchei Halacha glosses to the Kitzur Shulchan Aruch 116: 17) who ruled like the Rema and maintain that glass cannot be kashered. See next footnote.
 It is interesting to note that the Rema only explicitly argues on the Shulchan Aruch’s shitta regarding glass’s kasherability in Hilchos Pesach. Curiously, in Yoreh Deah, he makes no mention of a disagreement. This led many authorities to maintain that the Rema only meant to argue regarding kashering for Pesach due to the stringencies of chometz; however, for year round, such as issues regarding bassar b’chalav use, he would have agreed, that glass is non-absorbent and does not need to be kashered. These include the Knesses Hagedolah (Yoreh Deah 121 Haghos on the Tur 25; quoted by the Kehal Yehuda; both cited by the Sdei Chemed, Asifas Dinim, Maareches Hei 29), Minchas Yaakov (85: 12), Pri Megadim (Orach Chaim 451 Mishbetzos Zahav 31 s.v. da and Yoreh Deah 105 Mishbetzos Zahav 1 s.v v’im), Ya’avetz (Mor U’Ketziah end 451), Yad Yehuda (69, Pirush Ha’aruch 81, and beg. 105), Aruch Hashulchan (Orach Chaim 451: 9), Rav Shlomo Zalman Auerbach (Halichos Shlomo,Moadim vol. 2, Pesach Ch. 3, footnote 75), the Minchas Yitzchok (Shu”t vol. 1: 86; he adds that certainly haga’alah would work on glass for shaar issurim; this is also the opinion of the the Badatz Eidah Chareidis in their annual Madrich HaKashrus,Kashrus Habayis l’Pesach Ch. 3: 9; 5775, pg. 190; via haga’alah), and Rav Ezriel Auerbach (Piskei Rav Ezriel Auerbach on Hilchos Haga’alas Keilim 3; sent to me by Rabbi Yaakov Skoczylas; he adds that lechatchilla it is still preferable not to use the same glassware for both milchig and fleishig). However, the Biur HaGr”a (Yoreh Deah 135: 28) seemingly equates the two, implying that the dinim should be the same. Rav Yaakov Kamenetsky was machmir as well (Emes L’Yaakov on Tur and Shulchan Aruch, Orach Chaim 451: footnote 443) that according to the Rema, glass is always considered a Kli Cheres, absorbent and non-kasherable.
 Rema (Orach Chaim 451: 26) and Levush (ad loc 26). However, several Ashkenazic poskim, including the Rema himself, in his Darchei Moshe (ad loc. 19) maintain that this ruling is only lechatchila; ergo, b’dieved it would be permitted. The Taz (ad loc. 30) and Elyah Rabbah (ad loc. 54) maintain that in a b’dieved situation we may rely on the Shulchan Aruch’s opinion and kashering is not required, whereas the Magen Avrohom (ad loc. 49), Chok Yaakov (ad loc. 68), Pri Megadim (ad loc. Mishbetzos Zahav 30), Shulchan Aruch Harav (ad loc. 73), Chayei Adam (vol. 2, 125: 22), and Mishnah Berurah (451: 155) maintain that b’dieved only if it were actually kashered would glass be permitted for Pesach use. On the other hand, the Gr”a (Orach Chaim 451: 26 s.v. v’yesh), Kitzur Shulchan Aruch (116: 13), and Aruch Hashulchan (Orach Chaim 451: 50) understand that according to the Rema, kashering would not help a glass utensil, even b’dieved. The Mishnah Berurah concludes that b’makom hefsed merubah and after the glass kli is aino ben yomo one may rely on the Shulchan Aruch and Taz, that no kashering is needed, especially as the Pri Chodosh (ibid) and Ya’avetz (Mor Uketziah ad loc s.v. v’ra’isi; also citing his father the Chacham Tzvi) hold that it is ikar. The Minchas Yitzchok (Shu”t vol. 1: 86) maintains that technically speaking haga’alah should work on glass even for Pesach, based on the Ritva’s opinion; however, since this is not cited lemaaseh by the codifiers, one should only rely on it b’shaas hadchak. However, regarding year-round use, he concludes that one may indeed rely on kashering glass. This is also the opinion of the the Badatz Eidah Chareidis (in their annual Madrich HaKashrus,Kashrus Habayis l’Pesach Ch. 3: 9; 5775, pg. 190).
 These include the Pe’as Sadechah (Shu”t vol. 1: 78 s.v. uklei plastic; who holds they are similar to klei keren and one will not kasher it properly), Rav Yosef Shalom Elyashiv (cited in Shevus Yitzchok vol. 6, Ch. 5: 4, pg. 53 and Ashrei HaIsh, Orach Chaim vol. 3, Ch. 53: 16; however, he does allow kashering if the plastic kli absorbed taam via kli sheini), Rav Shmuel Halevi Wosner (in Kovetz M’Beis Levi vol. 1, ppg. 33 - 34 and vol. 3, pg. 20; however, he does allow kashering if the plastic kli absorbed taam via kli sheini), the Strasbourger Rav (Shu”t Kinyan Torah B’Halacha vol. 2: 84), Rav Nissim Karelitz (Chut Shani, Hilchos Pesach, Ch. 10, pg. 127), the Shaarim Metzuyanim B’Halachah (vol. 3, 116: 3 s.v. ode), Rav Nosson Gestetner (Shu”t Lehoros Nosson vol. 6: 69 and 101), Rav Menashe Klein (Piskei Mishnah Halachos on Hilchos Haga’alas Keilim 8; sent to me by Rabbi Yaakov Skoczylas) and Rav Ezriel Auerbach (Piskei Rav Ezriel Auerbach on Hilchos Haga’alas Keilim 8; sent to me by Rabbi Yaakov Skoczylas; however, he does allow kashering if the plastic kli absorbed taam via irui kli rishon or kli sheini). There is an interesting story told about Rav Elyashiv and his shittah on kashering plastic, as heard from MV”R Rav Yosef Yitzchok Lerner. Apparently, Rav Levi Yitzchok Halperin of Machon Technologia V’Halachah proved to Rav Elyashiv that scientifically haga’alah does indeed purge bleeyos from plastic. Unimpressed, Rav Elyashiv replied, ‘but can you prove that it removed all of the bleeyos?’
 This klal was first set by the Maseis Binyomin (Shu”t 94), and seconded by the Pri Megadim (Orach Chaim 451 Mishbetzos Zahav 31, end s.v. klei etzem). This is also seen regarding those who permitted Klei Adamah for kashering (see next footnote), as the Machatzis Hashekel (ad loc. 4 s.v. din klei adamah) writes that its din is not explained elsewhere. In other words, although there was no precedent for allowing it to be kashered, yet, the majority of Acharonim ruled that it nevertheless may be. This rule regarding plastic’s kasherability was later used by several contemporary authorities in including the Cheishev Ha’eifod (Shu”t vol. 1: 117 s.v. umayhei), and Rav Yosef Eliyahu Henkin (teshuva printed in Kovetz Am HaTorah vol 1, pg. 5; 5739).
 Magen Avraham (Orach Chaim 451: 4), Knesses Hagedolah (Yoreh Deah 121, Haghos on the Tur 18), Chok Yaakov (Orach Chaim 451: 12), Shulchan Aruch Harav (ad loc. 12), Pri Megadim (Sifsei Daas ad loc. 4), Aruch Hashulchan (ad loc. 8), and Mishnah Berurah (ad loc. 18). See previous footnote. However, several Acharonim, including theYad Yehuda (Yoreh Deah 69, Pirush Ha’aruch end 81 and Pirush Hakatzer 117), Darchei Teshuva (Yoreh Deah 121: 25), and the Chazon Ish (Orach Chaim 120: 2 s.v. M”A) argue that Klei Adamah should share the status of Klei Cheres and are therefore non-kasherable.
 Including the Minchas Yitzchok (Shu”t vol. 3: 67), Rav Yosef Eliyahu Henkin (teshuva printed in Kovetz Am HaTorah vol 1, pg. 5; however in Rav Shimon Eider’s Sefer Hilchos Pesach, II A 2: 3, he quotes Rav Moshe Feinstein as saying that Rav Henkin held that plastic does not need kashering as it is smooth), Shu”t Seridei Aish (vol. 2: 160; and in new print vol. 1, Orach Chaim 46: Inyan Rishon), Shu”t She’eilei Tzion (vol. 2: 23), Shu”t Cheishev Ha’eifod (vol. 1: 117 s.v. umayhei), Shu”t Chelkas Yaakov (vol. 2: 163; and new print vol. 3, Yoreh Deah 45), Shu”t Tzitz Eliezer (vol. 4: 6), Shu”t Eretz Tova (Orach Chaim 39; though he maintains to do it 3 times), the Tzhelemer Rav (cited in Netei Gavriel, Hilchos Pesach vol. 1, Ch. 64: footnote 17), Rav Moshe Aryeh Freund (sefer Mara D’Shma’atsa; cited in Ohel Yaakov, Kitzur Hilchos Kashrus L’Pesach pg. 77; though he maintains to do it 3 times), Shu”t Yeshuas Moshe (vol. 3, 46: 4), Shu”t Vayeishev Moshe (vol. 1; 45 and 46), Rav Ben Tzion Abba Shaul (Shu”t Ohr L’Tzion vol. 3, Ch. 10: 13), Rav Ovadia Yosef (Chazon Ovadia, Pesach vol. 1, pg. 151: 9 and footnote 39), Yalkut Yosef (Kitzur Shulchan Aruch, Orach Chaim 451: 38), Rav Mordechai Eliyahu (Darchei Halacha glosses to the Kitzur Shulchan Aruch 116: 17), and Rav Yisroel Belsky, citing this as the shittah of Rav Yaakov Kamenetsky (quoted in the OU’s Daf Hakashrus vol. 22, No. 7, 5774 / 2014; pg. 3: footnote 3). The Tzitz Eliezer (Shu”t ibid. s.v. v’yesh) adds that if one is worried that that the plastic kli might get ruined when being kashered, it may be kashered in a Kli Rishon that was just taken off the fire, as mentioned by the Shulchan Aruch Harav (Orach Chaim 451: 14) and Rav Yitzchok Elchanan Spektor (Shu”t Ein Yitzchok, vol. 1 Yorah Deah 13: 7) regarding utensils that absorbed taam, but not from direct heat from a fire.
 The Badatz Eidah Chareidis’ annual Madrich HaKashrus (Kashrus Habayis l’Pesach Ch. 3: 8; 5775 pg. 190).
 For example Shaarei Halacha (Efrati; 5), Yesodei Yeshurun (vol. 6, Ma’areches Hagaalas Keilim ppg. 170 - 173), Netei Gavriel (ibid.), Kitzur Shulchan Aruch (Pfeiffer; on Bassar Bechalav, vol. 2, pg. 36: 6), Sefer Haga’alas Keilim (Ch. 13: 301 and footnote 271), Shu”t Minchas Chein (vol. 1: 28, Ch. 5: 10; first published in Minchas Chein on Hilchos Pesach), and SeferHakashrus (Ch. 3: 56).
 Shu”t Ba’er Moshe (vol. 2: 53), Shu”t Minchas Yitzchok (ibid; who is more stringent regarding Pesach), Shu”t Igros Moshe (Orach Chaim vol. 2: 92 s.v. uvadavar kli), Rav Moshe Sternbuch’s Lekutei Teshuvos Vehanhagos (Hilchos Pesach; cited in Ohel Yaakov, Kitzur Hilchos Kashrus L’Pesach pg. 77), Rav Shimon Eider’s Sefer Hilchos Pesach (ibid.), Rav Avrohom Blumenkrantz’s annual Kovetz Hilchos Pesach (2006, pg. 88 and 92) and Rav Ezriel Auerbach (Piskei Rav Ezriel Auerbach on Hilchos Haga’alas Keilim 8; sent to me by Rabbi Yaakov Skoczylas; as long as it was heteira bala. SeferHakashrus (Ch. 3: 56) maintains that it is preferable not to kasher plastic for Pesach. Even Rav Elyashiv (ibid.), who although is machmir altogether with plastic, nevertheless allows year-round plastic to be kashered 3 times as long as it was ‘heteira bala’.
 In fact, Frenchman Gustave Boucharda created the first form of synthetic rubber in 1879.
 These sefarim who quote Rav Moshe as ruling stringently include Shaarim Metzuyanim B’Halacha (ibid.), Kitzur Shulchan Aruch (Pfeiffer; ibid.), Netei Gavriel (ibid.), Sefer Haga’alas Keilim (ibid.), Shu”t Kinyan Torah B’Halacha (ibid.), Shu”t Yeshuas Moshe (ibid.), Shu”t Lehoros Nosson (ibid.), Shu”t Vayeishev Moshe (ibid.), Shu”t Minchas Chein (ibid.), as well as Rav Shmuel Kamenetsky’s Kovetz Halachos (Hilchos Pesach pg. 110), Rav Moshe Sternbuch’s Lekutei Teshuvos Vehanhagos (Hilchos Pesach), and the Dirshu edition of the Mishnah Berurah (vol. 5, 451, Biurim U’Musafim 131; which actually makes a 3-way stirah in Rav Moshe’s shittah). Several of them are coming to agree with their understanding of Rav Moshe’s assessment, whereas many of them are coming to argue based on the klal of the Pri Megadim (see footnote 14) et al. that Chazal only specified Klei Cheres as non-kasherable; all other keilim should be kasherable. Several sefarim that this author has seen that quote Rav Moshe as only being stringent for Pesach include Rav Shimon Eider’s Sefer Hilchos Pesach (ibid.), Mesores Moshe (ibid.) and Sefer Hakashrus (ibid.).
 Yesodei Yeshurun (vol. 6, Ma’areches Hagaalas Keilim ppg. 170 - 173), Rav Shimon Eider’s Sefer Hilchos Pesach (II A 2: 3), Rav Avrohom Blumenkrantz’s annual Kovetz Hilchos Pesach (2006, pg. 88), and Mesores Moshe (pg. 138: 269)
 See Rabbi Yitzchok Dovid Frankel’s Kuntress Yad Dodi (Hilchos Hechsher U’Tevillas Keilim, Question 19).
 Since plastic was not mentioned by Chazal or Rishonim, perhaps its status is similar to Klei Even and Adamah and deemed kasherable, or perhaps similar to glass. If it is considered similar to glass, perhaps it does need to be kashered at all. Hence we hold that haga’alah should indeed work.
Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.
L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda.