Updated February 2023
As the Yom Tov of Pesach nears, and the diligent balabusta begins to tackle the challenge of preparing the kitchen for Pesach, undoubtedly the light at the end of the tunnel is beginning to shine. Although moving into a separate Pesach home sounds very inviting, such luxuries are often not affordable and definitely not in the Pesach spirit. Among the basic mitzvos of the chag is the mitzvah of tashbisu se’or mibateichem, ridding one’s home and possessions of chometz. However, if we are to use kitchen equipment, utensils, or articles that can be found in our kitchen year-round, it may be insufficient to just clean them thoroughly. One is forbidden to use these items unless they have been especially prepared for Pesach. This preparation process is known as kashering.
The Torah instructs us that the proper kashering method used to rid a vessel of chometz is dependent upon the original method of food preparation through which chometz was absorbed into the vessel.
When possible, it is preferable for a person knowledgeable in the laws of kashering to be present during the kashering process. Kashering must be finished before the latest time to burn the chometz (see here). If kashering was not done before this time, consult your rav. For Kashering Safety Tips from Hatzalah, see here.
Kashering methods can be broadly grouped into one of the following categories:
|Libun Gamur||Heating metal to a glow|
|Libun Kal||Heating metal above the temperature that will burn paper|
|Hagola||Purging through immersion in hot water|
|Iruy Roschin||Purging through a hot water pour|
It is important to note that where libun kal helps, certainly libun gamur is good; where hagola helps, surely libun kal is good; and where iruy helps, certainly hagola and libun help.
We will now discuss how to properly kasher or prepare kitchen appliances and cookware for Pesach using one of the above-described kashering methods.
Kashering the Oven
No part of the stove can be considered kashered for Pesach unless it is completely clean and free from any baked-on food or grease. This includes the oven, cooktop, and broiler.
In a conventional oven, whether gas or electric, an oven cleaner may be necessary to remove baked-on grease. Be sure to check hidden areas including corners, door edges, the area behind the flame burners, and the grooves of the rack shelves. If a caustic type of oven cleaner (such as Easy-Off) was used to clean the oven, and some stubborn spots remained after a second application with similar results, the remaining spots may be disregarded. Once the oven and racks have been cleaned, they may be kashered by libun kal. The requirement of libun kal is satisfied by turning the oven to broil, or the highest setting for 40 minutes. In a gas oven, the broil setting will allow the flame to burn continuously. In a conventional electric oven, the highest setting (550°F) kashers the oven. Only libun kal is required for the oven racks, since it is usual to cook food in a pan and not directly on the racks themselves.
In a self-cleaning oven, before using the self-clean cycle, one should clean the inside face of the oven door as well as the opposing outer rim of the oven outside the gasket, since these areas are not necessarily cleaned during the cycle. One should ensure that the gasket itself is clean on the area outside the oven seal. (NOTE: The gasket is sensitive to abrasion.) The self-cleaning cycle will then clean and kasher the oven simultaneously.
Caution: There is a potential risk of fire during the self-cleaning process, especially if there is a build-up of grease on the bottom of the oven. It is recommended that one apply Easy Off, made especially for self-clean ovens, to lift and remove the grease. The oven should not be left unattended while in the self-cleaning mode.
Most oven manufacturers instruct the consumer to remove the oven racks before self-cleaning so they will not discolor. However, one may self-clean the oven with the racks inside even though they might discolor. After the self-clean cycle, one should use a little oil on the side of the racks to easily slide them in and out of the oven. There are some manufacturers that also require removal of the racks before the self-clean cycle can start. In this case, one should take the racks out, clean them very well, and then put them in the oven at the highest temperature (usually 550°F) for 40 minutes. This procedure kashers the racks.
Some ovens come with a convection feature. This feature allows for more uniform heat distribution by using a fan to circulate the heat. If the convection oven has the self-cleaning feature it will be sufficient to also kasher the fan using the self-clean kashering method previously mentioned. If there is no self-cleaning feature, the entire oven including the fan while it is circulating, must be sprayed with a caustic cleaner and cleaned well. The oven should then be kashered by turning it on to the 550°F setting for forty minutes.
Please note that many ovens today have ‘Aqualift’ or ‘Steam Clean’ instead of a conventional self-cleaning feature. Neither ‘Aqualift’ nor ‘Steam Clean’ get hot enough to kasher the oven. Instead, use the Conventional Oven kashering method as described above.
Oven Hoods and Exhaust Fans
Hoods and exhaust fan filters should be cleaned and free of any food residue.
Broiler and Broiler Pan
The broiler pan cannot be kashered by merely turning on the gas or electricity. Since food is broiled or roasted directly on the pan, the pan must be heated to a glow in order to be used during Pesach. This can be done by the use of a blowtorch (but only by qualified and experienced individuals). It is recommended they do this in a darkened room to more easily observe when the metal is glowing. An alternative method is to replace the broiler pan.
The empty broiler cavity must then be kashered by cleaning and setting it to Broil for 40 minutes. If one does not intend to use the broiler, one may still use the oven even without kashering the broiler, provided that the broiler has been thoroughly cleaned.
Other inserts such as griddles, which come into direct contact with food, are treated the same as broiler pans. Therefore, they would also require application of direct heat until the surface glows red. Otherwise, the insert should be cleaned and not used during Pesach.
Warming drawers cannot be kashered because the heat setting does not reach high enough to constitute libun. The warming drawer should be cleaned, sealed, and not used during Pesach.
When microwaves are used, they do not necessarily absorb chometz. The microwave should be tested to see if the walls become hot during use. To do this, one should cook an open potato in the microwave until it has been steaming for a few minutes. Immediately after the potato has been cooked, one should place his hand on the ceiling of the microwave to see if it has become too hot to touch. If one cannot hold his hand there for 15 seconds, we assume that the microwave has absorbed chometz. If this is the case, the microwave should be cleaned and sealed for Pesach. If it has not absorbed chometz (i.e., one can hold his hand there for 15 seconds), the microwave itself needs only to be cleaned well.
It is recommended that one wait 24 hours before using the microwave on Pesach. The turntable should be replaced because it has come into contact with hot food and would not pass the hand test. One may replace the turntable with a ¼” Styrofoam board.
Microwave ovens that have a convection or browning feature must be kashered using the convection and/or browning mode. The kashering method used would be libun kal. The convection microwave should first be cleaned well. If the fan area cannot be properly cleaned, it should be sprayed with a caustic cleaner (e.g., Easy Off) while the fan is on, and rinsed off before kashering. One should then test the convection microwave to see if it reaches the required heat for libun kal by putting it on its highest setting for 40 minutes. A piece of paper should then be held against the interior wall to see if it gets singed.1 If the paper is singed, the convection microwave has been heated sufficiently for libun kal and can be considered kashered. Many models fail the test because their settings do not allow the microwave to become hot enough for kashering. If this is the case, the microwave should be cleaned, sealed, and not used during Pesach.
Kashering The Cooktop
On a conventional gas range, the cast iron or metal grates upon which the pots rest may be inserted into the oven after they have been thoroughly cleaned. The grates can then be kashered simultaneously with the oven. (If kashering with a self-clean cycle, the grates do not need to be cleaned first. However, it is advisable to check with the manufacturer as to whether the grates would be able to withstand a self-clean cycle. Some grates have rubber feet that may be damaged by the heat of the oven or may damage the oven itself.) Note: The self-cleaning cycle may remove the paint finish if the grate is not manufactured to withstand the self-clean cycle.
The rest of the range (not glasstop) should be cleaned and covered with a double layer of heavy duty aluminum foil, which should remain on the range throughout Pesach.
Please Note: Extreme caution should be taken not to cover over the vent so as to allow the oven heat to escape. The drip pans should be thoroughly cleaned and need not be kashered. The burners and caps do not require kashering or covering but should be cleaned.
In a conventional electric cooktop, one is required to clean the burners well and then turn them on to a high heat setting until they are glowing hot. (This usually takes only several minutes.) The drip pans should be thoroughly cleaned and need not be kashered. The remaining cooktop areas should be cleaned and covered. The knobs with which the gas or electricity is turned on and off should be cleaned. No other process is necessary to kasher the knobs.
Please Note: All ovens ventilate hot steam during cooking. In the past, the hot steam was ventilated through the back of the oven. Today, many ranges no longer ventilate in this manner. The oven steam is ventilated through one of the rear cooktop burners. During oven cooking, if the rear vented burner is turned off and covered by a pot or kettle, the hot steam will condense on the burner and utensils. This could create hot zei’a (condensate) that can cause serious kashrus problems with the utensil if the food cooked in the oven is a meat product and the pot on the burner is dairy or pareve, or vice versa. Care should be exercised with the vented burner to keep it clear during oven cooking or baking.
Caution: When placing aluminum foil over the oven backsplash, be careful not to trap the heat coming from the oven vent between the foil and the backsplash; doing so may melt the backsplash if the oven vents through the back.
To kasher a Sensi-Temp burner for Pesach, remove the burner from the range top by lifting it up halfway to vertical and pulling it out. Clean it well and wait 24 hours. Once that time has elapsed, pour boiling water over the sensor, which is located in the middle of the burner. Insert the burner back into its socket by reversing the extraction steps. Turn the burner on to its maximum setting until it glows (about 2 minutes).
Electric Cooktop with Glass Surface
Kashering a glass-ceramic electric cooktop for Pesach use is a bit complex. To kasher the burner area, one should clean it well and turn on the elements until they glow. The burner area will then be considered Kosher for Passover. However, the remaining area that does not get hot is not kashered. The manufacturers do not suggest covering this area as one would a porcelain or stainless steel cooktop, as it may cause the glass to break. Real kosherization can be accomplished by holding a blowtorch over the glass until it is hot enough to singe a piece of newspaper upon contact with the glass. However, this may cause the glass to shatter and is not recommended.
As the area between the burners cannot practically be kashered, it would be wise to place a trivet on the open glass area so the pots can be transferred.
In order to use a large pot that extends beyond the designated cooking area, STAR-K recommends one of these solutions: (1) Use a cooktop mat specifically made for glass stovetops.2 (2) Place a metal disc approximately 1/8 of an inch thick onto the burner area in order to raise the Passover pots above the rest of the glass surface. (CAUTION: This disc should not extend beyond the designated cooking area.) Or, (3) Use a stovetop heat diffuser made specifically for glass stovetops. Should a pot boil over, the resulting trickle could serve as a conduit from the Pesachdig pot to the non-Passover stovetop, posing a halachic concern; the above suggestions will help mitigate those concerns.
NOTE: Caution should be taken to obtain devices that will not harm the surfaces. Cooking efficiency may be compromised when using these devices.
Gas Cooktop with a Glass Surface
For gas stovetops with a glass surface, one may kasher the grates by putting them into the oven with libun kal (550°F for 40 minutes). In most such models, the grates cover the entire top of the stove and there should be no problem adjusting pots on the stovetop. Food which falls through the grates and touches the glass surface should not be used.
For those models where the grates do not cover the entire cooktop surface it would be wise to place a trivet on the open glass area so that pots may be transferred. No food or pots may come into direct contact with the non-kashered glass surface.
Some gas cooktops have an electric warming area on the glasstop. In order to kasher this area, it would have to become red hot when turned on. Many of these warming areas do not become hot enough for kashering and may not be used on Pesach.
Before kashering an induction cooktop, it must be thoroughly cleaned and then left unused for at least 24 hours. The cooktop then requires iruy roschin. (Refer to instructions below for kashering a stainless steel sink by using iruy roschin.)
Note: Induction cooktops are not permitted to be used on Shabbos and Yom Tov.
Kashering Barbecue Grills
Note: Kashering a grill can be dangerous and should only be performed by competent individuals.
A grill cannot be kashered by simply turning on the gas or electricity. Since food is roasted directly on the grill, it must be heated to a glow in order to be used. This can be done by sandwiching the grates between the charcoal briquettes and setting them on fire. An alternative method is to replace the grates of the grill. The part of the grill cavity which is level with the grate must also be kashered by heating it to a glow. This is due to the likelihood of food having touched that area during barbecuing. The empty gas grill cavity (and the hood) must be kashered by cleaning, closing the hood, and setting it to the highest setting for 40 minutes. In the case of a regular grill, the cavity should be filled with charcoal briquettes which should be set on fire.
Other inserts such as griddles, which come into direct contact with food, are treated the same as a grill and would, therefore, also require application of direct heat until the surface glows red. Otherwise, the insert should be cleaned and not used during Pesach. If the grill has side burners, they should be treated like cooktop grates, assuming no food has been placed directly on them. It is easier to determine that the metal has been brought to a glow in a darkened room.
Kashering Metal Utensils
Metal utensils (e.g., stainless steel/cast iron/aluminum serveware; silver/pewter bechers/Kiddush cups) that have been used for cooking, serving, eating, or washed with hot chometz may be kashered. This may be done by cleaning the utensils thoroughly and waiting 24 hours before immersing them, one by one, into a Kosher l’Pesach pot of water heated to a rolling boil. A rolling boil should be maintained while the vessel is immersed.
Note: Follow these steps with care! The metal utensil or vessel should be submerged into the boiling water for about 15 seconds. The utensils undergoing the kashering process may not touch one another. In other words, if a set of flatware is being kashered for Pesach, one cannot take all the knives, forks and spoons and put them into the boiling water together. Each of these items should be placed into the boiling water separately.
KASHERING TIP: Loosely tie the pieces of silverware to a string, leaving three inches between each piece, and immerse the string of silverware slowly, making sure the water keeps boiling.
The process is finalized by rinsing the kashered items in cold water. If tongs are used to grip the utensil, the utensil will have to be immersed a second time with the tongs in a different position so that the boiling water will touch the initially gripped area. Unlike tevilas keilim, the entire utensil does not have to be immersed in the boiling water at once; it may be immersed in parts.
A non-Kosher l’Pesach pot may also be used, l’Halacha, for the purpose of kashering if it is clean and has not been used for 24 hours. However, it is customary to make the pot Kosher l’Pesach before using it for kashering. This is accomplished by cleaning the pot, both inside and out, and leaving it dormant for 24 hours. The pot should then be completely filled with water and brought to a rolling boil. Using a pair of tongs, one should throw a hot stone or brick into a pot that has been heated on another burner. The hot rock will cause the water to bubble more furiously and run over the top ridge of the pot on all sides at one time. (One should use caution, as the hot water may spray in all directions.) The kashering process is finalized by rinsing the pot in cold water. The pot may now be refilled, brought to a boil, and used to kasher the chometz utensils. It is a minhag to re-kasher the pot again after kashering if it is intended for Pesach use.
EXTRA BONUS: After this kashering process has taken place, the status of these newly kashered utensils may be changed from milchig to fleishig or vice versa, or pareve.
Kashering / Preparing Kitchen Sinks for Use on Pesach
Sinks are generally made from either stainless steel, granite composite, china, porcelain enamel, or man-made materials such as Corian.
Stainless Steel Sinks
Can be kashered using iruy roschin, as follows: Clean the sink thoroughly. Hot water should not be used or poured in the sink for 24 hours prior to kashering. It is recommended that the hot shut-off valve under the sink be turned off 24 hours before kashering. The sink should be dry before kashering. Kashering is accomplished by pouring boiling hot water from a Pesach kettle/pot over every part of the stainless steel sink.
TIP: If a roasting pan is filled and heated, the pouring surface is much wider than a kettle spout. It is not sufficient to pour water on one spot and let it run down the sink. The poured water must touch every part of the sink, including the drain and the spout of the water faucet. It is likely that the kashering kettle will need to be refilled a few times before kashering can be completed. After kashering, the sink should be rinsed with cold water. If hot water was accidentally used in the sink during the 24-hour dormant period, and there is not enough time before Pesach to leave the sink dormant for an additional 24 hours, a shaila should be asked.
These sinks cannot be kashered and should be cleaned, not used for 24 hours, and completely lined with contact paper or foil. The dishes that are to be washed should not be placed directly into the sink. They must be washed in a Pesach dish pan which sits on a Pesach rack. It is necessary to have separate dish pans and racks for milchig and fleishig dishes.
Porcelain, Corian or Granite Composite Sinks
These sinks should also be considered similar to a china sink, since there is a controversy as to whether these materials can be kashered. Granite composite is a material fashioned from granite and plastic. Many sinks that look like granite are actually granite composite.
Silestone, Porcelain Enamel, Corian, Quartz, Plastic/Formica and Granite Composite countertops cannot be kashered; they should be cleaned and covered. To place hot food and utensils on these countertops, cardboard or thick pads must be used to cover the counter. Corian is also a form of plastic that cannot be kashered. Since the chometz penetrates only a thin layer of the counter, it can be sanded down to take off a layer of Corian (the thickness of a piece of paper) and is considered Kosher l’Pesach. However, only a qualified contractor should attempt this procedure.
Pure Granite (not granite composite), Marble, Stainless Steel, or Metal may be kashered through iruy roschin. Wood may also be kashered through iruy roschin if it has a smooth surface.
Iruy rochsin is accomplished by pouring boiling hot water over every part of the clean countertop. Actual water is needed to kasher, not steam. A steam machine may be used if it boils water and sprays it onto the countertops. However, if the steamer only produces steam and not actual boiling water, it can not be used to kasher, even if the steam is hotter than 212oF. STAR-K has tested many models of steamers available commercially and has found that almost all of them will only produce hot steam and not boiling water. One method of iruy rochsin is to spray or pour a small amount of hot water on the counter and then use a hot iron or heated cast iron plate on top of the water which will [re-]boil it on contact. However, this is dangerous and should only be performed by competent individuals.
Kashering Glass Drinkware
In pre-war Europe, where glass was expensive and hard to obtain, it was customary to kasher drinking glasses by immersing them in cold water for three periods of 24 hours. This is accomplished by submerging the glasses for one 24 hour period. The water should then be emptied, refilled and allowed to sit for another 24 hours. The procedure should be repeated a third time, for a total of 72 hours. This method of submerging cannot be used for Pyrex or glass that was used directly on the fire or in the oven. Arcoroc and Corelle should be treated similar to glass for kashering purposes.
In general, kashering glasses is recommended only in cases of difficulty. Wherever glasses are readily available for purchase, special glasses for Pesach are preferable.
For other items or questions, feel free to call or email the STAR-K Institute of Halacha at 410.484.4110 or [email protected]
1. השיעור של קש נשרף עליו הוא מבחוץ וכאן הוא מבפנים, אבל בתנורים שלנו א”א להבחין אם נשרף עליו מבחוץ, מפני שיש לתנור שני כותלים וביניהם חומר המקיים את החום, וא”א להגיע לבחוץ של כותל הפנימי. ונ”ל שכשפותחים את התנור ונכנס אויר קר לתוך התנור, אז הכותל הפנימי מבפנים הוא יותר קר מכותל הפנימי מבחוץ שמכוסה מכל הצדדים.
2. NOTE: STAR-K certifies Kosher Cooktop Mats. For purchasing details, please call 718-755-7083.