Kashering Your Kitchen for Pesach


ravmoshe-heinemann-1By Rabbi Moshe Heinemann, Star-K Rabbinic Administrator

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 from chometz. However, if we are to use kitchen equipment, utensils, or articles that are used 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 unique preparation process is known as kashering.

We are instructed by the Torah that the proper kashering method one uses to rid a vessel of chometz depends upon the original food preparation method used which absorbed chometz into the vessel. Kashering methods can be broadly grouped into four categories:
Libbun – Incinerating
Hagola – Purging
Eruy Roschim – Purging through a hot water pour
Milui V’eruy – Soaking

It is preferable, when possible, that a person who is knowledgeable with the laws of kashering be in attendance during this kashering process.

Libbun is divided into two categories:

  • Libbun Gamur: Heating Metal To A Glow
  • Libbun Kal: Heating Metal So That Paper Will Burn On The Other Side Of The Heated Utensil

Metal utensils used in the oven for baking, must be heated to a glow if they are to be used on Pesach.


The stove must also be kashered if it is to be used for Pesach. This includes the oven, the cooktop, and the broiler. 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.

The Oven
In a conventional oven, 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 libbun kal. The requirement of libbun kal is satisfied by turning the oven to broil or the highest setting for forty minutes. In a gas oven, the broil setting will allow the flame to burn continuously. In a conventional electric oven, the highest setting (broil or 550°F) kashers the oven. Only libbun kal is required for the oven racks since it is usual to cook food in a pan, not directly on the racks themselves.

In a continuous cleaning oven, one cannot assume that such an oven is clean because the manufacturer claims it to be continuously clean. A visual inspection is required. Since caustic or abrasive oven cleaners, e.g. Easy Off, cannot be used without destroying the continuous clean properties of the oven, a non-abrasive and non-caustic cleaner must be used to clean the oven. Grease spots will usually disappear if the top layer of grease is cleaned with Fantastic and a nylon brush. Then the oven should be turned on to 450°F for an hour so that the continuous clean mechanism can work. If the spots don’t disappear, the oven should be left on for a few hours to allow the continuous clean mechanism to deep clean, or else the spots should be removed with oven cleaner or steel wool. If the spots are dark and crumble when scratched they can be disregarded. In all of the above cases, the oven should then be kashered by turning it to the broil setting for forty minutes.

In a self-cleaning oven, clean the inside face of the oven door, as well as the opposing outer rim of the oven outside the gasket (as these areas are not necessarily cleaned during the cycle. Easy Off manufactures one product that is safe for self-cleaning ovens.) Ensure 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. The oven should not be left unattended while in the self-cleaning mode.

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 kasher the fan as well. 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 its highest setting for forty minutes.

The Cooktop
On a conventional gas range, the cast iron or metal grates upon which the pots on the range are placed, 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.) The rest of the range (not glass top) 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, as well, so as to allow the oven heat to escape. The drip pans should be thoroughly cleaned and need not be kashered. The burners do not need kashering or covering, just cleaning.

In a conventional electric cooktop, one needs 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 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 is covered by a pot or kettle, the hot steam will condense on the burner and utensils. This could create hot zea (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. Caution: When putting 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.

Kashering a Glass, Corning, Halogen or Ceran electric smoothtop range for Pesach use is a bit complex. To kasher the burner area, clean well and turn on the elements until they glow. The burner area is now considered kosher for Pesach. 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 top, 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 on 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 transfered. In addition, in order to use a large pot that extends beyond the designated cooking area, one should 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.) This will also help in case a small pot boils over, sending a trickle of hot liquid that would serve as a connector from the Passover pot to the non-Passover stovetop. (Note: Cooking efficiency may be compromised when using a metal disc.)

For gas stovetops with a glass surface, one may kasher the grates by putting them into the oven with a libbun kal (550°F for forty 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 onto the open glass area so that pots may be transfered.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. This area would have to become red hot when turned on in order to kasher. Many of these warming areas do not get hot enough for kashering and may not be used on Pesach.

The Broiler
The broiler pan cannot be kashered by just turning on the gas or electricity. Since food is broiled or roasted directly on the pan, it must be heated to a glow in order to be used. This can be done by using a blowtorch (which should only be done by qualified and experienced personnel). An alternate method is to replace the broiler pan.The empty broiler cavity must then be kashered by cleaning and setting it to broil for forty minutes. If one does not intend to use the broiler, he 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. If not, the insert should be cleaned and not used for Pesach.

Barbeque Grills – A grill cannot be kashered by just 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 either by using a blowtorch (which should only be done by qualified and experienced personnel) or by sandwiching the grates between the charcoal briquettes and setting them on fire. An alternate 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 the food having touched that area during barbequeing. The empty grill cavity must be kashered by cleaning, closing the hood and setting it to broil for forty minutes.

Other inserts, such as griddles, which come into direct contact with food are treated the same as a grill. Therefore, they would also require application of direct heat until the surface glows red. If not, the insert should be cleaned and not used for Pesach. If the grill has side burners, they should be treated like cooktop grates, assuming no food has been placed directly on it.
Practical Tip: It is easier to determine that the metal has been brought to a glow in a darkened room.

Warming Drawers – Warming drawers cannot be kashered because the heat setting does not reach high enough to constitute libbun. The warming drawer should be cleaned, sealed, and not used for Pesach.

Oven Hoods and Exhaust Fans – Hoods and exhaust fan filters should be cleaned and free of any food residue.

Microwaves – 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, cook an open potato in the microwave until it has been steaming for a few minutes. Place your hand on the ceiling of the microwave to see if it has become too hot to touch. If you cannot hold your hand there for fifteen 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., you can hold your hand there for fifteen seconds), the microwave itself needs only to be cleaned well. It is recommended to wait twenty-four hours without use before using the microwave for Pesach. The turn table should be replaced because it has come into contact with hot food and would not pass the hand test. One may replace the turn table 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 to be used would be libbun 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, with the fan on, and rinsed off before kashering. One should then test the convection microwave to see if it reaches the required heat for libbun kal by putting it on its highest setting for forty minutes. A piece of paper should then be held against the interior wall to see if it gets singed. 1 If so, the convection microwave has been sufficiently heated for libbun kal and can now be considered kashered. Many models fail the test, though, because their settings do not allow the microwave to get hot enough for kashering. If this is the case, the microwave should be cleaned, sealed, and not used for Pesach.

HAGOLA (Note: Follow these steps carefully)
Metal utensils that have been used for cooking, serving or eating hot chometz may be kashered. This may be done by cleaning them thoroughly and waiting
24 hours before immersing them, one by one, into a kosher for Pesach pot of heated water, one by one. The water should be heated and a rolling boil should be maintained when the vessel is immersed.

The metal utensil or vessel should be submerged into the boiling water for about fifteen seconds. The utensils undergoing the kashering process may not touch each other. 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. They should be placed into the boiling water separately. A special kashering suggestion is to 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. The entire utensil does not have to be kashered at once; it may be done in parts.

A non-kosher for Pesach pot may also be used for the purpose of kashering. It is the custom to make the pot kosher for Pesach before using it for kashering. This can be accomplished by cleaning the pot inside and out and leaving it dormant for 24 hours. The pot should then be completely filled with water, which has come to a rolling boil. Using a pair of tongs, throw in a hot stone or brick 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. (Use caution, as the hot water may spray in all directions.) The kashering process is finalized by rinsing the pot in cold water.

Extra Bonus: After the Pesach kashering process has taken place, the status of these newly kashered utensils may be changed from milchig to fleishig, vice versa or pareve.

Sinks are generally made from either stainless steel, granite composite, china, porcelain enamel, steel, or Corian.

Stainless steel sinks can be kashered using the following method. 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. Dry the sink before kashering. Kashering is accomplished by pouring boiling hot water from a Pesach kettle/pot over every part of the stainless steel sink. 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 the kashering can be completed. After kashering, the sink should be rinsed with cold water. If hot water was used in the sink accidentally 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.

China sinks cannot be kashered at all. These sinks 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 or Corian sinks should also be considered similar to a china sink, since there is a controversy as to whether these materials can be kashered.

Countertops – Silestone, Porcelain Enamel, Corian, and Plastic/Formica 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, but 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). It then is considered kosher for Pesach. However, only a qualified contractor should attempt this procedure. Pure Granite (not granite composite), Marble, Stainless Steel, or Metal may be kashered through eruy roschim. Wood may also be kashered through eruy roschim if it has a smooth surface.

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 and refilled and alowed to sit for another 24 hours. This procedure should be repeated a third time, for a total of 72 hours. This procedure of submerging cannot be used for Pyrex or glass that was used directly on the fire or in the oven. In general, kashering glasses is only recommended in cases of difficulty. Wherever glasses are readily available for purchase, special glasses for Pesach are preferable. Arcoroc and Corelle should be treated as glass for kashering purposes.

It’s important to note that where libbun kal helps, certainly libbun gamur is good; where hagola helps, surely libbun kal is good; where eruy helps, certainly hagola and libbun help.

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