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Practical list of items and how they are to be Kashered:
Pots, Cutlery and Kitchenware
Forks/Spoons: All forks, spoons and other cutlery made of Kasherable material, such as silver or stainless steel, are to be Kashered through Hagala.
Knives: It is a Mitzvah Min Hamuvchar for all those who have the capability of doing so, to buy new knives for Pesach. However, from the letter of the law, doing Hagala to them suffices [and one may certainly rely on this if it is not so feasible for him to get new knives]. One must sharpen the blade prior to doing Hagala in order to remove any rust the blade may contain. If the knife contains a handle and the blade is inserted into the handle, then it cannot be Kashered due to the inability to remove the Chametz from in between the crevices. Likewise, if the blade is attached to the handle with glue, it cannot be Kashered.
The custom is to Kasher cups through Miluiy Veiruiy or Hagala. One may not swerve from this custom. [If, however, one knows for certain that the Chametz was never used with hot Chametz. such as it was never used with a hot Chametz drink, and was never washed with hot water in a Chametz sink, and never had cold Chametz, such as beer, soak in it for 24 hours, and it never soaked in the water of a Chametz sink for 24 hours, then it does not need to be Kashered. Practically, however, it is difficult to ascertain the above as well as we suspect that perhaps a crumb of Chametz once fell inside, and therefore it is to initially be Kashered in all cases.]
Bedieved: If one used the cup for a hot Pesach drink without previously Kashering it, the drink remains Kosher [so long as the cup was not Ben Yomo of Chametz use at the time it was used for hot Pesach food].
Glass cups: Glass cups are not Kasherable, as explained in the previous Halacha.
Whether or not a pot may be Kashered is dependent on the material that it contains and how it was used-See Halacha 7-8! If the pot is made of a Kasherable material, such as metal without a Teflon or enamel coating, then if it is used for cooking with liquid it requires Hagala. If used for baking or frying with minimal oil, then it requires Libun Chamor as explained next.
Teflon/Enamel: If the pot is coated with enamel or Teflon then it may not be Kashered. See Halacha 8!
Do the handles of pots and pans need to be Kashered? From the letter of the law, the handles of the pot or pan do not need to be Kashered and certainly one need not worry of the cracks that they contain [which may have food in them]. Nevertheless, initially one is required to clean it and do Hagala to it, or do Iruiy Keli Rishon without needing a stone, as at times they are washed with hot Chametz.
Do pot covers need to be Kashered? The cover of a pot requires Hagala to be performed to it.
A pot or pan used to fry Chametz foods with a nice amount of oil, requires Hagala. If, however, one fried food in it using very little oil, just enough so the food does not stick, then the pot requires Libun Gamur.
Teflon/Enamel: A frying pan/pot which contains an enamel or Teflon coating, may not be Kashered, as explained in Halacha 8.
Must one Kosher his water urn to use on Pesach?
Water urns are to be Kashered for Pesach. In the following cases, this may be required from the letter of the law: a) The urn was placed down while hot onto Chametz; or b) The urn was washed in a sink with hot Chametz; or c) One had Chametz soak in the urn for 24 hours; or d) One poured hot water from the urn onto Chametz [such as onto instant noodles, a Chametz soup mix, or he poured the leftover hot water into a Chametz sink]; or e) One heated a Chametz food, such as bread, on top of the urn. If one is certain that none of the above took place with the urn, then from the letter of the law, it is not required to be Koshered. Practically, however, it is difficult to ascertain the above as well as we suspect that perhaps a crumb of Chametz once fell inside, and therefore it is to initially be Koshered in all cases.
How to Kosher: If the urn is made of metal, then it is to be Kashered through Hagalah. If it contains plastic, it is disputed if it can be Kashered, as explained in Halacha 8. In all cases, one must beware to remove the hardened calcium from the urn before Kashering.
Grater and grinder:
Appliances and furniture
The grates: The grates of the stove need to be Kashered through Libun Chamur. [If one cannot do Libun Chamor to the grates, then one is to clean them very well and wrap the grates in thick aluminum foil that will not tear throughout Pesach. Practically, it is customary to cover all grates with tinfoil even if it was Kashered through Libun Chamur, as explained below]
Burners: The burners are to be Kashered through Libun Kal. One is to first lean the burners well. It is advised to use toothpicks or needles to remove any dirt or food from within the gas holes of the burner. Afterwards, one is to turn on the fire for some time to accomplish Libun Kal.
Stove top surface: The stove top requires Iruiy Keli Rishon. One is to clean the stove surface well and then do Iruiy Keli Rishon to it. If the surface is made of non-Kasherable material, such as enamel, that it must be covered with aluminum. Furthermore, it is customary to cover all stovetops with tinfoil even if it is made of a Kasherable material, as explained below.
Knobs: One is to clean the knobs of the stove very well, cover them or attach clean replacement knobs.
Covering all items: Practically, the custom is that even after Kashering all the above parts of the stove, one covers all the surfaces with aluminum. [See Halacha 5 in Q&A]
From the letter of the law, an oven requires Libun Chamur. If one’s oven does not have a self clean cycle, it is very difficult to accomplish this. One cannot do Libun Chamur through using a blow torch, as the oven can break in the process. One is thus to buy a Pesach oven or alternatively Kasher it in the following way:
- Clean the oven well using a Chametz killing agent such as bleach or oven stain remover.
- Wait 24 hours prior to Kashering.
- Turn the oven on for a period of at least one hour to its highest temperature or blow torch the oven from the inside.
- After the Kashering process is complete, one should cover the walls and floors with aluminum foil.
Self cleaning oven:
An oven with self cleaning mode reaches a temperature of 900° F and is equivalent to Libun Chamur. An oven with a “Continuous cleaning” cycle is not equivalent to Libun Chamur, and hence the above-mentioned method must be used.
Electric hot plate [Shabbos Plata]:
Some Poskim rule an electric plate requires Libun Chamur. Others rule an electric plate requires Libun Kal. Others rule it requires Iruiy Keli Rishon. If the coating of the hot plate is made of enamel, then it is not Kasherable. Practically, if possible, one is to purchase a new electric hot plate for Pesach. In a time of need, one is to clean the entire hot plate, including the cord, its sides, and bottom areas, with a killing agent such as bleach. After 24 hours pass, one is to then turn the hot plate on to its hottest setting for some time and then pour boiling water over it. One is to then cover the hot plate with a thick piece of tinfoil. For extra care, one can place a second sheet of tinfoil or aluminum pan on the hot plate.
Does it need to be Kashered? Some Rabbanim say that a microwave does not need to be Kashered at all prior to use for Pesach, and simply needs to be wiped clean. The majority consensus of Poskim, however, is that a microwave requires Kashering, and thus cannot be used for Pesach in its un-Kashered state. Practically, one must abide by the latter opinion, as the former opinion does not take all factors into account and is hence inaccurate. According to all, a combination microwave oven, which is both an oven and a microwave, requires Kashering. We will now discuss if and how a microwave can be Kashered:
How to Kasher it: Some Poskim rule that it is not possible to Kasher a microwave. Other Poskim rule it can be Kashered through steaming water inside it. This is accomplished through doing the following steps: The microwave is to be cleaned, not used for 24 hours, and have water with bleach or soap placed in it and heated for about 10-20 minutes, until it steams out. Practically, one is to purchase a new microwave for Pesach. If this is not possible, and one is in need to use the microwave, then one is to do as stated above, and use a hermetically sealed container to cook the food, as stated next.
Cooking in a hermetically sealed container: In all cases, it is permitted to cook in a microwave, Pesach food that is contained within a hermetically sealed container which does not allow any vapor to escape or enter. This applies even if the microwave has not been Kashered, and certainly if it has been Kashered in the method mentioned above. Some Poskim, however, discourage using the microwave in this method as it occurs that the hermetic sealing tears or opens during the cooking, which would then pose a Kashrus issue. It is therefore best to only use the microwave in this method after first Kashering it.
Some Poskim rule it is not possible to Kasher a microwave. Other Poskim rule a microwave does not need to be Kashered at all. Other Poskim rule it can be Kashered through steaming water inside. This is accomplished through the following steps: The microwave is to be cleaned, not used for 24 hours and have water with bleach placed in it and heated for about 10-20 minutes, until it steams out. Practically, one is to purchase a new microwave for Pesach. If this is not possible, then one is to do as stated above, and use a hermetically sealed container to heat the food.
A fridge, and its various compartments, does not require Kashering [i.e. Hagala] but simply Hadacha [washing] as it is generally only used for cold foods. [One is to wash the fridge down very well using water and a Chametz killing agent, such as bleach and the like.] However, if one is accustomed to place foods into the fridge even while they are still hot [such as a pot of Chametz soup prior to cooling down] then the custom of all Jewry was to perform Iruiy Keli Rishon.
The elastic insulating side: One must take special care to clean well from Chametz crumbs the elastic insulation that surrounds the doors of the fridge. A suggestive form of cleaning is to use Q-tips dipped in bleach.
The freezer: One is to defrost any ice from the freezer and clean it out.
Covering the shelves: The custom is to cover the shelves of the fridge. This is not required from the letter of the law. [See Halacha 5 in Q&A]
Bedikas Chametz: One is to perform Bedikas Chametz to his fridge prior to entering the Pesach foods back into it, and prior to covering it shelves. [See Chapter 4 Halacha 2!]
Cord: One is to clean the electric cord of the fridge that enters into the outlet.
The actual sink: A sink needs to be Kashered. The Kashering of a sink is dependent on its material. A metal sink can be Kashered through Iruiy Keli Rishon. Most sinks, however, are made of porcelain or enamel which are non-Kasherable materials. Nevertheless, the custom is to do Iruiy Keli Rishon on even non-Kasherable material sinks. One then places a plastic sink insert into the sink which will be used throughout Pesach. [If one does not have a sink insert available, he is to cover the interior of the sink with tinfoil.]
The spout: The custom is to clean and wash the spouts of the sink, as throughout the year they have been used with hands that are dirty from Chametz. [One is to pour boiling water over the spout, and leave it open with the hot water running for a few moments.]
Knobs: One is to wash and clean the knobs of the faucet.
The drain: One should pour boiling water that contains bleach or Drano down the drain.
Metal strainer: The metal strainer which rests in the spout is to have Iruiy Keli Rishon performed on it.
Not to pour hot water in an unKashered sink on Pesach: One is initially to be careful not to use hot water that is over Yad Soledes [110° F] on Pesach, in a sink that is not Kasherable. This applies even if one has a sink insert. Thus, one should not turn on the hot water to the point of Yad Soledes and is likewise not to pour hot water into the sink so long as it is Yad Soledes, even if it is in a Keli Shelishi or Revi’i. [Accordingly, if one has a pot with hot water, he is to wait until it cools down prior to pouring it into a non-Kashered sink. One can mix cold water into the hot water in order to achieve this quicker.] If the water is warm, below Yad Soledes, it may be poured into the sink. Nonetheless, Bedieved, if one poured hot water into the sink, everything remains permitted, even it was very hot and was poured from a Keli Rishon.
It is customary of all Jewry to Kasher counters and tables that are used with hot foods during the year. Likewise, tables which are used without a tablecloth during the year, or are used with a thin cotton/linen/polyester tablecloth, are to be Kashered. However, tables that are only used with a thick or plastic/PVC tablecloth during the year, from the letter of the law do not need to be Kashered.
How to Kasher: Counters and tables are to be Kashered with Iruiy Keli Rishon and Even Meluban.
Is my table/counter a Kasherable material? Marble counters, and wooden tables are Kasherable. Quarts counters [i.e. engineered stone] are not Kasherable. Plastic tables are disputed if they are Kasherable. [See Halacha 8!] Practically, in all cases that the counter/table cannot be Kashered one is to nevertheless Kasher them with Iruiy Keli Rishon and then cover them with tinfoil, or PVC, as explained next.
Covering the counter or table: If one covers his table or counter with a thick tablecloth, PVC, or tinfoil, then from the letter of the law it does not need to be Kashered, as explained in Halacha 5. Likewise, if the counter or table has been Kashered, then from the letter of the law it does not need to be covered. Nonetheless, the custom of Jewry is to do both; to Kasher the table/counter and then cover the surface with tinfoil or PVC, as explained in the Q&A.
The walls of the counter: The walls surrounding the counters are to have Iruiy Keli Rishon performed and are then to be covered.
Must one cover all kitchen surfaces such as tables, counters, cabinets, refrigerator shelves and the like?
From the letter of the law, once these areas have been properly cleaned and Kashered they may be used for all foods without any cover. However, some Poskim rule that one is to cover the surfaces even after they are Kashered due to suspicion that perhaps they still contain actual Chametz that was not properly removed. Practically, the widespread custom is to cover all items that contact food even after they have been cleaned and Kashered.
It is best to buy new tablecloths for Pesach. Nevertheless, from the letter of the law, one may Kasher and use the tablecloths that he used during the year. The following is how they are Kashered: One is to wash them with hot water and laundry detergent.
Teeth; Fillings and Braces:
Natural teeth without fillings and the like: Teeth do not have to be cleaned or Kashered from the letter of the law. Nevertheless, the custom is that after finishing eating Chametz on Erev Pesach, one brushes his teeth, and cleans and wash them well with water prior to the start of the 5th hour on Erev Pesach, to make sure that no crumb of Chametz has remained in one’s teeth.
Teeth with fillings: Although there is much argument to be made that fillings do need not to be Kashered from Chametz, nevertheless, the Rabbinical directive given is to clean them out prior to the 5th hour on Erev Pesach, and then swish one’s mouth with the hottest temperature water from a Keli Sheiyni, that he can intake. It is best to not eat hot Chametz 24 hours prior to doing so. [Although this is a mere stringency and is not required.]
Braces: It is a Hiddur for one who wears braces to have the braces removed by a dentist before Pesach, and have them cleaned and Kashered. If this poses difficulty, then one is to clean them to the best of his ability, and follow the above-mentioned order for fillings.
Dentures: Dentures are preferably to be removed, cleaned and Kashered with Iruiy Keli Rishon before the 5th hour on Erev Pesach. If this is not possible, then one is to clean them to the best of his ability, and follow the above-mentioned order for fillings.
Toothpaste: It is customary to purchase Kosher for Pesach toothpaste. See Chapter 5 Halacha 4 in Q&A!
Seemingly, a pacifier does not require Kashering as it is never used for hot Chametz. However, it is best to clean it well and then Kasher it, or purchase a new one for Pesach.
It is not necessary to clean or purchase a new broom stick for Pesach, as even if it contains Chametz, it is less than a Kezayis, is dirty, and are nullified. [See Chapter 3 Halacha 2!] Nonetheless, some are particular to buy a new broom for Pesach.
Based on the above law, it is not necessary to change the vacuum bag before Pesach, as even if it contains Chametz, the individual pieces are less than a Kezayis, are dirty, and are nullified. Nonetheless, the custom is to do so.
List of vessels and their Kashering status
|Aluminum||Kasherable based on use|
|Baking Pan||Libun Chamor [Are thus not Kasherable]|
|Burners of stove top||Libun Kal|
|Ceramic||Cannot be Kashered|
|China||Cannot be Kashered|
|Counter||Iruiy Keli Rishon with Even Meluban|
|Cups||Cannot be Kashered unless made of metal, in which case needs Hagala|
|Earthenware||Cannot be Kashered|
|Enamel||Custom is not to Kasher for Pesach|
|Frying pan||If coated with enamel or Teflon, may not be Kashered. If not coated, may be Kashered based on use.|
|Glass||Cannot be Kashered|
|Grates of stove top||Libun Chamur|
|Kiddush Cup [silver or metal]||Hagala|
|Knives||Best not to Kasher for Pesach; if Kasher needs sharpening and Hagala|
|Plastic||Dispute amongst Poskim if may be Kashered.|
|Pot [not coated with enamel]||Hagala. If used to fry without oil-Libun Chamor.|
|Porcelain||Cannot be Kashered|
|Pyrex||Dispute amongst Poskim if may be Kashered.|
|Sink spout||Clean and wash|
|Sink made of enamel/ceramic/glass/plastic||Cannot be Kashered|
|Sink made of metal||Iruiy with even Meluban|
|Skewer for barbecue||Libun Gamor|
|Steel [including stainless steel]||Kasherable [Hagala/Libun] based on use|
|Stove top [enamel]||Cannot be Kashered|
|Stove top [stainless steel]||Iruiy Keli Rishon with Even Meluban|
|Teflon||Cannot be Kashered|
|Toaster Oven||Do not Kasher. Sell to gentile and put away|
|Wood [without cracks]||Hagala|
|Wood [with cracks]||Cannot be Kashered|
 Admur 451:26
Background: According to some Poskim, one only needs to wash them spotlessly clean, and may then use them for even hot foods. The reason for this is because we judge after majority usage, and the above items are majority only used for cold or Keli Sheiyni foods. However, today the custom is to do Hagala to all dishes and cutlery as we suspect for the opinion who says that we judge even after the minority usage of the vessels. [Admur ibid]
 Admur 451:14
 Admur 451:15
 Admur 451:19-20
 Admur 451:20
 Admur 451:72
 The reason: As at times Chametz soaks for 24 hours inside the liquid that is in the cup and it is considered like the Chametz was cooked in it. This is certainly possible by wine or [hot tea] of which it is common to dip biscuits or pastries inside of them and perhaps some crumbs have remained in their liquid for the above amount of time. Likewise, some people drink beer in their cups and the beer remains in the cup for 24 hours. Now, although this is only the minority use of the cup, while its majority use is for cold foods, nevertheless, it is subject to the dispute in Poskim as to whether we follow majority or even minority use, of which we conclude that Lechatchila we suspect for the stringent opinion. [Admur ibid; See Admur 451:26-31] Likewise, as times one washes the cup with hot water together with other Chametz, and at times the cup soaks in the Chametz sink water for 24 hours. [See Admur 451:21]
 Admur 451:21 regarding the handle of a pot and the same should apply here as well; Admur 451:46 regarding a grinder
 Admur 451:19
 The reason: As the lip is external and there is thus no worry that Chametz entered inside. [Admur ibid]
 Admur 451:21; Chok Yaakov 451:40
 Admur ibid; Rama 451:12; Taz 451:17
 Admur ibid; Peri Chadash 451:!3; Chok Yaakov 451:40
 Admur 451:41
 Piskeiy Teshuvos 451:10
 Piskeiy Teshuvos ibid
 Admur 451:36-37; ; Michaber Y.D. 121:4
 Admur 451:37; This applies only when Kashering for Pesach, however by other Issurim, the pot needs Libun. [Admur ibid]
 Admur 451:36
 See Even Yisrael 7:21; Piskeiy Teshuvos 451:14; Nitei Gavriel 84:8
 Nonetheless, even in these cases it is subject to dispute, as some Poskim rule we follow majority usage. However, according to the final ruling that we are accustomed to suspect for minority usage, then the above cases become an obligation to Kosher due to the custom. [See Admur 451:26-27]
 See Admur 451:21
 See Admur 451:60 and 72
 See Admur 451:51 regarding Minhag Nashim to not use the pot used to Kosher with Iruiy Keli Rishon due to Nitzuk Chibur; See Rama Y.D. 105:3; Darkei Teshuvah 105:96-100
 See Shach Y.D. 105:23; P”M 173 A”A 1 that it possibly transfers 60x since there is liquid inside; Maharsham 5:76 that it only transfers a Kelipa
 See Piskeiy Teshuvos ibid who records a dispute regarding if we suspect that perhaps a crumb of Chametz fell into it, however, from Admur 451:21; 43 and 72 it is implied that there is no room for such suspicions, and only if there is probable cause is there reason to be stringent. However, see Admur 451:46 regarding a grinder, that initially we do suspect for a crumb of Chametz. Vetzaruch Iyun.
 Admur 451:21 regarding the handle of a pot and the same should apply here as well; Admur 451:46 regarding a grinder; See previous footnote
 An electric urn can be Koshered through boiling water inside of it until its very top and then throwing into the boiling water an Even Meluban [red hot stone or slab of metal] which will cause the water to overflow and splash beyond the rims of the pot. [Admur 452:1 and 24]
 See Piskeiy Teshuvos ibid
 Admur 451:54
 The reason: As we suspect it was used to grind Chametz, or to grind a Charif food [such an onion] which was cut with a Chametz knife. [admur ibid]
 The reason: As we suspect that a crumb of Chametz remained on the grinder and has now gotten into one’s food. [Admur ibid]
 Admur 451:46
 The reason: From the letter of the law, it does not require Kashering if it was not used to grind bread or other Chametz, however initially it is good to Kasher it due to suspicion that perhaps one time a crumb of Chametz fell inside, and it was then ground with a Davar Charif. [Admur ibid] Certainly, if one grinds onions and garlic, or other Charif foods, in this grinder, and the foods were cut with a Chametz knife, then the grinder must be Kashered from the letter of the law. [See Admur 451:54 regarding a grater]
 The reason: As a) Everything is cold and does not transfer taste. B) From the letter of the law we do not need to suspect that a crumb of Chametz fell inside. [Admur ibid] c) We follow majority usage Bedieved. [Admur 451:28]
 Piskeiy Teshuvos 551:19
 Admur 451:24; Rav Wozner in Kuntrus Mibeis Levi 1:29
Other opinions: Some Poskim rule it only requires Libun Kal. [M”B 451:34; Igros Moshe 1:124; Piskeiy Teshuvos ibid]
 The reason: As at times [Chametz such as] dough spills onto them and they absorb Chametz directly without liquid. [Admur] Now, although we rule that two pots which touch each other do not transfer taste without liquid [Admur 451:67] perhaps we suspect that liquid may spill onto while cooking and make everything prohibited according to our custom to prohibit the food even if the pot is not be Ben Yomo.
 See Admur 451:65; 67; Rama Y.D. 92:8; Taz Y.D. 92:29; M”B 451:34; Halacha 5 above!
 In any event the pots never touch the burners and there is thus no suspicion that Chametz absorbed without liquid will transfer into the food in the pot. Nevertheless, Libun Kal is to be performed in order to destroy any Chametz Beiyn from inside, and Kasher it from majority usage.
 Admur 461:1; Piskeiy Teshuvos 551:10
 The reason: As the Chametz at times falls onto the floor of the oven and the oven walls receive Chametz taste directly without liquid [Admur ibid] and we are initially stringent to follow minority usage. [Admur 451:27] Now, although we rule that two pots which touch each other do not transfer taste without liquid [Admur 451:67] perhaps we suspect that liquid may spill onto while cooking and make everything prohibited according to our custom to prohibit the food even if the pot is not be Ben Yomo.
 The heating elements are very delicate and can burn due to the heat of the blow torch. [Piskeiy Teshuvos ibid footnote 39]
 Admur 461:1 regarding oven floor; Nitei Gavriel 79:7; Shevach Hamoadim p. 178 [regarding an electric stove top];
 The reason: As whenever Chametz is heated on a vessel without water it requires Libun Chamor. [Admur 451:13] And at times one places Chametz, such as Challahs, directly on the hot plate [see 451:58] and we go after Miut Tashmish on Pesach [Admur ibid; 451:26] and it is thus similar to the stovetop grates which require Libun Chamor. [Admur 451:24] However Tzaruch Iyun, as according to this then also counters and tables should require Libun Chamor, and in 451:58, even according to the stringent approach, it only requires Iruiy with Even Meluban. Perhaps the explanation is that only when there is fire directly touching the vessel does it require Libun Chamor, and thus by a table, despite it having hot Chametz directly on it, it does not need Libun Chamur, as there is no actual fire touching it. Vetzaruch Iyun regarding a Plata, as although there is no fire, nevertheless there is electric heat directly under the metal and it is thus similar to baking Chametz on an electric stove top.
 M”B 451:34 and Igros Moshe 1:124 regarding grates; Opinions brought in Siddur Pesach Kehilchaso 7:4; Hagalas Keilim 13:381; Piskeiy Teshuvos 451:19; Hakashrus 6:22
 Opinions brought in Siddur Pesach Kehilchaso 7:4; Hagalas Keilim 13:381; Piskeiy Teshuvos 451:19; Hakashrus 6:22
 See Piskeiy Teshuvos 451:49; Hakashrus ibid footnote 61
 Harav Asher Lemel Hakohen told me that he suggests to all to purchase a new one for Pesach as it is very difficult to clean.
 As by doing so all the Chametz is considered destroyed even if some Chametz was unable to be removed and went unnoticed.
 As all vessels are to be non-Ben Yomo when Kashered through Hagala or Iruiy Keli Rishon [Admur 452:15]
 Brought in Siddur Pesach Kehilchaso 7:4; Hagalas Keilim 13:381; Piskeiy Teshuvos 451:19; Hakashrus 6:22
 By doing so one secures that even if the Plata was not Kashered properly, such as according to those who require Libun Chamur, then it is nevertheless useable due to the metal interval. Nevertheless, one is to also Kasher the hot plate beforehand even though he plans to cover it as at times the tinfoil tears and liquid comes in between.
 To secure that even if the bottom tears and receives liquid, there is nevertheless an upper interval.
 See Piskeiy Teshuvos 451:22; Sefer Hakashrus [Fuchs] 1:47-50 [pp. 48-49]; Nitei Gavriel 80:16; See also Hadarom Choveret 6 Nissan 5722; Kovetz Beis Aaron Yisrael 4:3
How does a microwave cook? A microwave is a rapid cooking element, which can warm and cook food much quicker than traditional cooking methods. Now, how does the microwave achieve its rapid cooking? The microwave does not use the heat of a fire or electricity to cook but rather cooks the food using radiation, or radio electromagnetic waves, which is projected from a vacuum tube and bounced off the metal lined walls of the microwave which penetrate the food from all sides. These waves hasten the movement of the water molecules in the food to atomic levels hence generating heat. [Heat is generated from movement and friction.] This form of cooking, cooks the food much quicker than fire or electricity, as the radioactive waves hits the food equally in all areas and furthermore, penetrates the inside of the food molecules hence making the entire mass of the food an equal recipient of the heat. This is unlike fire or electric cooking which heats the external part of the food, and that heat then must travel to the inner part of the food in order to cook it. Likewise, this form of cooking only heats the actual food, as it does not actually send heat to the food but causes the food to heat itself up. Accordingly, all other areas and items of the microwave might remain cold, including the walls and certain plastic or glass containers which cover the food. The only way these items will become hot is if they are in contact with the food itself. The radio waves harmlessly pass through these containers into the food and do not cause any heating within them being they do not contain water molecules or other polar charge component. [See Hakashrus ibid footnote 100; See here for an educational video on how a microwave works. https:::www.youtube.com:watch?v=kp33ZprO0Ck]
 Rav Yitzchak Yosef, the current Chief Rabbi of Israel
 The reason: As the actual walls of the microwave do not heat up at all, and only the food itself heats up.
 See all Gedolei HaPoskim mentioned in Hakashrus ibid and Piskeiy Teshuvos ibid, which include Rav Wozner, Rav Elyashiv, Rav Sheinberg, Rav Halbershtam; Nitei Gavriel ibid footnote 26 in name of Rav Neiman of Montreal
 The reason: a) Although the walls of the microwave do not heat up, nevertheless, the steam and spills of the food make the walls absorb the food and hence it must be Kashered. [Piskeiy Teshuvos ibid; See Admur 451:41, Michaber 451:14, and M”B 451:81 that a vessel which absorbed the steam of an Issur requires Hagala] b) As there is a vent duct in the microwave that contains actual steam of food, and that area is not Kasherable. [Rav Neiman ibid]
 As although the walls don’t heat up, the microwave receives steam from the foods and hence must be Kashered.
 See Piskeiy Teshuvos ibid; Siddur Pesach Kehilchaso 8:3 that it can only be Kashered through Libun, Hagala or Iruiy Keli Rishon and Even Meluban
 The reason: a) Although the walls of the microwave do not heat, nevertheless the steam and spills of the food inside make the walls absorb the food and hence it must be Kashered. Now, it is not possible to Kasher the microwave, as one cannot blow torch it, or place it in boiling water, and many Poskim rule an item cannot be Kashered through steaming water inside it. [See Shoel Umeishiv Telisa 3:125; Sdei Chemed Mareches Hei 24; Chametz Umatzah 17:12 that it is not possible to Kasher through vapor] It therefore has no viable path for Kashering. A second reason is b) As there is a vent duct in the microwave that contains actual steam of food, and that area is not cleanable or Kasherable. [Rav Neiman ibid]
 Teshuvos Vehanhagos 2:212; Yalkut Yosef Pesach p. 360; Piskeiy Teshuvos ibid regarding Shaas Hadechak
 The reason: As we rule that it is possible to Kasher an item through steam, and just like the microwave absorbed the food through steam, so too it can be Kashered through steam. [See Peri Chadash 121; P”M Y.D. 94 M”Z 1; Tevuos Hasadeh 3:3]
 See Hakashrus ibis footnote 105 that so ruled Rav Wozner, Rav Shternbuch and Rav Mordechai Eliyahu
 Piskeiy Teshuvos ibid writes to leave it on for one hour; Sefer Hakashrus ibid writes [based on Mitbach Kehalacha p. 58 and Techumin 8:21] to enter a half a liter of water and leave the microwave on until it steams out; Rav Yitzchak Yosef says to leave it on for six minutes
 Teshuvos Vehanhagos 2:212; Koveitz Mibeis Levi 3:22; 7:25; Yalkut Yosef Pesach p. 360; Piskeiy Teshuvos ibid; Hakashrus ibid
 Piskeiy Teshuvos ibid; Hakashrus ibid footnote 105; Nitei Gavriel ibid concludes that due to the many opinions, one is not to use it for Pesach without directive from a Rav
 Hakashrus ibid; Nitei Gavriel ibid in name of Rav Neiman
 Pischeiy Halacha Kashrus p. 28; Piskeiy Teshuvos ibid footnote 106
 See Kovetz Mibeis Levi 3:22-9; Hadarom ibid; Beis Aaron Veyisrael ibid
 Admur 451:58; Nitei Gavriel 76:4
 The reason: As at times the hot Chametz soup spills onto the shelves. [Admur ibid] This is no longer widely practiced today, seemingly due to that we are careful never to place hot foods in a fridge, or due to that anyways we are accustomed to cover the shelves.
 Piskeiy Teshuvos 451:11
 The reason: As it has likely absorbed Chametz through a) Pouring hot Chametz, or Chametz water into it [i.e. draining the pot of pasta]; b) Having Chametz soak in it for 24 hours. C) Washing Chametz dishes with Yad Soledes water. [See Admur 451:21 regarding the handle of a pot and the same should apply here as well; Admur 451:46 regarding a grinder] and we are initially stringent to follow minority usage. [Admur 451:27] Now, if it is not Kashered, we suspect that perhaps one will pour hot Pesach food into it [Nitzuk], or have Chametz vessels soak in it for 24 hours, or wash Pesach dishes with hot water, during Pesach and make everything prohibited according to our custom to prohibit the food even if the pot is not be Ben Yomo. [However, if its majority usage is with cold, then the food remains Kosher.]
 Admur 451:77 regarding the spouts of wine barrels
 Piskeiy Teshuvos ibid
 The reason: As the sink has absorbed Chametz, as stated above, and on Pesach we are initially stringent even regarding a Keli Sheiyni transfer and even if not Ben Yomo, and even if the Chametz absorption was only due to minority usage. [Admur 451:27 and 33; 72]
 See Admur 451:34
 As Bedieved we follow majority usage by a non-Ben Yomo Chametz vessel [Admur 451:27 and 31 and 72] and hence since the sink’s majority use is with cold products, it is therefore Kosher Bedieved.
 Admur 451:58 regarding tables; Piskeiy Teshuvos 451:44
 The reason: As at times people place a hot pot on them, and the pot spills, thus requiring Kashering of Iruiy Keli Rishon [according to the Poskim who rule we follow minority usage]. Furthermore, at times, people place actual hot Chametz directly on the counter, and it hence requires Hagala, or Iruiy Keli Rishon with Even Meluban. [Admur ibid] Nonetheless, Bedieved, if one placed a hot pot/food directly on the table or counter without Kashering it, everything remains Kosher as we follow majority usage by a non Ben Yomo item. [Admur 451:27 and 72]
 See Admur ibid that if it is not common to place hot foods on them, then Kashering is not necessary; See Halacha 5 for the law of a covering and the differences between materials!
 Michaber 451:20; Admur 451:58
 M”A 451:38 in name of Maharil [even regarding tables]; Elya Raba 451:40 [only regarding shelves, not tables]; M”B 451:115 [brings both opinions]; Dvar Moshe Tinyana 98:36; See Nitei Gavriel 77:1 footnote 2
Does this law apply even to tables and counters or only to shelves? The M”A ibid applies the ruling of the Maharil to all surfaces that contact food, including tables. However the Elya Raba ibid limits this stringency of the Maharil to cabinets with shelves in which it is difficult to clean the corners of Chametz, and hence it is to be covered. However, a flat surface such as a table, even the Maharil agrees that there is no need at all to cover it. The M”B ibid brings both opinions and seems to side with the ruling of the Elya Raba. So also rules the Aruch Hashulchan 451:41. Nevertheless, it is customary of Jews, including Anash, to be stringent in this matter.
Opinion of Admur: Admur ibid completely omitted the ruling of the Maharil; M”A and Elya Raba. He only mentions the necessity to cover an item in 451:48 regarding vessels made of wood that are constantly used with dough and flour; and in 451:65 regarding an oven that was not Kashered. No mention is made anywhere regarding covering an already Kashered table or cabinet. Nevertheless, it is customary of Jews, including Anash, to be stringent in this matter. [See Nitei Gavriel ibid]
 M”A ibid; Piskeiy Teshuvos 451:44
 Admur 453:23-24; Piskeiy Teshuvos 451:42
 The reason: As it is very difficult to ascertain that not even one crumb of Chametz will remain stuck to the cloth. [Admur ibid regarding the sacks for flour]
 See Yad Yitzchak 3:78; Darkei Teshuvah 89:11; Sdei Chemed 4:24; Minchas Yitzchak 8:37; Minchas Shlomo 2:46; Shevet Halevi 1:148; 4:74; Tzitz Eliezer 9:25; Mishneh Halachos 3:56; 4:68 and 93; Piskeiy Teshuvos 451:23; Nitei Gavriel 78
Background: The idea of Kashering teeth, fillings or dentures is not recorded in the Talmud or classical Poskim and was first dealt with amongst the more recent authorities. Aside for the status quo custom to not make an issue of this throughout the year regarding meat and milk, the Poskim suggest various explanations for why they do not pose a Halachic problem that require Kashering, such as 1) The material of the teeth, filling or dentures are smooth and do not absorb; 2) One never enters hot food in his mouth of a temperature that can transfer taste. Practically, while the Poskim agree that from the letter of the law no Kashering is required, regarding Pesach, it is proper to be stringent. [See Piskeiy Teshuvos ibid footnotes 107-110]
 Setimas Haposkim who all omit any obligation or reminder of cleaning the teeth prior to the 5th hour on Erev Pesach.
 Darkei Chaim Veshalom 568; See Poskim ibid
 As even by actual Chametz vessels waiting 24 hours prior to the 5th hour is a mere custom and is not required from the letter of the law.
 Nitei Gavriel 78:4
 Poskim ibid
 See Admur 451:54 regarding a grater that we suspect a Chametz crumb has been leftover, and it hence requires Libun Chamor
 Nitei Gavriel 78:3
 We do not suspect that perhaps hot Chametz spilled on it the same way we do not suspect this for a cup or any other item that was only used with cold Chametz!
 See Nitei Gavriel 76:6