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Koshering Appliances and Utensils

Koshering Appliances and Utensils


The basic principle to bear in mind when koshering is that the way the non-kosher food substance is absorbed into the walls of the utensil is the way it is expelled. Hence, a pot used for stewing can be koshered by boiling; a pan used for frying or baking can be koshered only by blowtorching (direct contact with heat).


Stoves may be divided into three parts: the oven, the cook top, and the broiler. No part of the stove can be koshered unless it is completely clean, and free from any baked-on food or grease.

Gas and Electric Oven
The most difficult item to kosher properly is the oven, because it requires an absolutely thorough cleansing. Please note the following steps in cleaning:

  • The oven should not be used for twenty-four hours prior to koshering.
  • Spray all internal surfaces of the oven with a chemical cleanser to remove all surface dirt.
  • Disassemble the inner parts of the oven: remove grates, the shelf separating the oven from broiler, remove the entire broiler and its drawer.
  • Check all of the above surfaces for dirt. Use chemical cleanser a second time, scrub with steel wool, screwdriver, and/or a scraper to remove remaining spots. Carefully check difficult areas (use a flashlight, if necessary): internal corners, door edges, the area behind the flame burners, and the grooves of the broiler tray shelves. CAUTION: Do not disturb the thermostat wire. The interior of oven should look new.
  • Reassemble the oven. Set the oven dial to broil for one hour.

Note: Unless the broiler tray is blowtorched until it glows red, food should never be placed directly on it. Cover the tray with the aluminum foil or place food in a pot or pan on the broiler tray.

  • Some have the custom of blowtorching the interior surfaces of the oven in order to assure the removal of any remaining dirt.

Self-Cleaning Oven
In a self-cleaning oven, the self cleaning cycle will clean and kosher the oven simultaneously. This is true as well for convection ovens with a self-cleaning feature. To kosher the oven, follow the manufacturers instructions for the self-cleaning cycle.

Continuous-Cleaning Oven
In continuous cleaning ovens, one cannot assume that such ovens are actually clean simply because of claims made by the manufacturer. 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. Grease spots will usually disappear if the top layer of grease is cleaned with Fantastic and a nylon brush. Turn the oven on to 450º F for several hours, so that the continuous clean mechanism can work. Try to remove those spots which don’t disappear even after the use of the continuous clean mode. If that doesn’t work, if they are dark and crumble when scratched, they may be disregarded. Now the oven is ready for koshering. Turn oven to highest setting, either 550º or broil, for forty minutes.

Gas Range Tops

  • Disassemble and remove grates (spiders), burner jets, drip trays, and the entire oven top if possible.
  • Clean with steel wool, soap and water.
  • Clean the entire surface under top of the oven.
  • Reassemble the cooking surface and ignite the fire under the grates at top heat until they glow red (15-20 minutes). If possible, invert grates so that they get closer to the fire source.

The grates can also be koshered by insertion into the oven after they have been thoroughly cleaned. The grates can then be koshered simultaneously with the oven.

Electric Range Tops
Koshering a smooth top electric range, e.g. glass, Corning, Halogen or Ceran, is more problematic. The elements of the stove can be turned on until they come to a glow. The burner areas are now considered koshered. Regarding the rest of the cook top, the only way to kosher it is to expose the entire surface area to direct heat until it is hot enough to singe a piece of newspaper upon contact. This method however, may cause the glass to crack and is therefore not advised. Consequently, one should keep the area between the burners clean and dry or avoid placing hot pots on the non-koshered surfaces.

In an electric cook top (coil burners), one only needs to turn on the burners to a high heat setting for several minutes in order to kosher them.

The Broiler
As mentioned previously, the broiler pan and grill can be koshered only by using direct heat, using a blowtorch, causing them to glow red. This is necessary because non-kosher food may have been cooked directly on the pan or grill. If this method is not feasible, the simplest procedure is to replace the pan with a new pan and kosher the empty broiler cavity by cleaning and setting it to broil for forty minutes. If one does not intend to use the broiler, one may still use the oven, provided that the broiler has been thoroughly cleaned.

Other inserts such as griddles or barbecue broilers which come into direct contact with food are treated the same as broiler pans. Therefore, they too would require application of direct heat until the surface glows red. If the inserts are not going to be used, they only need to be cleaned.

Practical suggestion: It is easiest to determine that metal has been brought to a glow at night with the lights shut off.

Microwave Oven
Clean the microwave oven thoroughly and put a vessel with a few ounces of water in the oven. Allow the water to vaporize into steam.

Microwave models with browning or convection features must be treated like regular ovens.There is no practical way to kosher them.


Cutlery made of one piece of metal can be koshered. However, any utensils which will be damaged by boiling water cannot be koshered. Any utensils that have crevices in them that cannot be thoroughly cleaned cannot be koshered. Utensils with wooden or bone handles which have no crevices in them and will not be damaged by boiling water, may be koshered. Thoroughly clean the utensils of food and rust (especially at the joints). Wait twenty-four hours. Kosher the cutlery by dropping them, one by one, into a pot of boiling water. Make sure that the water is actually boiling when you place the cutlery in the pot. Remember that placing the utensils in the pot often lowers the temperature of the water below the boiling point. The utensils must be left in the pot until the water bubbles. With the addition of each piece of cutlery be sure the water continues to bubble.

  • Large utensils may be koshered in the water, one side at a time. Make certain that the part that you are immersing is completely surrounded by water.
  • Remove the utensil and rinse in cold water. To help with removal, use tongs or a mesh basket. Note: If tongs are used to insert the utensil into the boiling water, reposition them so that the original area they touched can now be exposed to the hot water. Return the utensil to the boiling water.


In all cases below, thoroughly clean the utensils to be koshered and wait 24 hours.

There are two ways to kosher pots:

  • This is the same process described above for cutlery, except immersion is for a longer period of time. Fill a kosher pot with water and boil. Immerse the pot requiring kosherization for 15 seconds while maintaining a rolling boil. The pot need not be completely submerged all at once; it can be immersed piecemeal, lowering each part into the water and keeping it there for 15 seconds. After koshering, rinse the koshered pot in cold water.
  • If the pot to be koshered is too big to submerge in another pot, fill it with water to the very top. Boil the water. Heat a large stone or other piece of metal. Using a pair of tongs, throw the heated stone or metal into the pot causing the water to overflow the top of the pot. WARNING: Be very careful not to get scalded by the boiling water shooting out from the pot. Pour out the water and rinse the pot with cold water.

If non-kosher food was fried in oil in a frying pan, one can kosher the pan by heating it to the point that paper will become singed when in contact with the other side of the heated metal. If it was used without oil, it is not feasible to kosher it since it must be heated until it glows red-hot which almost always will ruin the pan. Teflon or enamel coated pots cannot be koshered.


A sink made of metal can be koshered by pouring boiling water over the entire sink. (The water must be boiling right before you pour it.) Porcelain sinks cannot be koshered.

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Anonymous Chicago December 3, 2017

Does it matter what kind of pot you use, meat or milk when you kosher a utensil? Does it make it dairy if dairy? Reply

Mendel Adelman December 4, 2017
in response to Anonymous:

Great question!

The Alter Rebbe writes in his Shulchan Aruch (Siman 452:15) that although technically, the pot that you are kashering on does not make the pots inside it dairy or meat during the kashering process, the custom is to kasher the large pot first, and only then use it to kasher other pots.

That way, whatever you kasher remains pareve.

In the event that you can't kasher the larger pot or you don't have any pareve pots large enough, you should speak to a rabbi. Reply

Anonymous London April 5, 2017

Koshering glass for Pesach How can you kosher drinking glasses and glass bowls for Pesach? Reply

Simcha Bart for April 6, 2017
in response to Anonymous:

According to many authorities, glassware cannot be Koshered at all. Please consult your own rabbi to determine the custom in your community if and how to Kosher glassware. Please see here for more information on the subject. Reply

Candace Ladson, SC January 16, 2017

As always I am amazed and humbled by your dedication to God and His laws. Thank you for sharing this. Now I understand why my Jewish friends don't eat at my house. I always wondered but was scared to ask. I didn't want to offend or make anyone feel uncomfortable or like an outsider. Now it makes sense. Reply

Anonymous September 19, 2016

Really helpful and well written! Thanks for posting! Reply Staff August 1, 2016

seasoning cast iron You can use vegetable oil to season your cast iron skillet. It works well!

(Note that most cast iron comes pre-seasoned and needs to be koshered first. This can be done by blow-torching it until it is red hot, or by putting it in the oven for a self-clean cycle. After this, you can season it with kosher oil and use as needed.) Reply

Sol E April 6, 2017
in response to Staff:

Vegetable oil becomes toxic at high temperatures. Do not use vegetable oil for cooking. Reply

Anonymous Manhattan July 26, 2016

cookware? The non-kosher way of seasoning a cast iron skillet is by using pork fat. What's the kosher way? Reply

Anonymous April 27, 2017
in response to Anonymous:

Olive oil or coconut oil Reply

Simcha Bart for Los Angeles July 13, 2016

You can immerse a new utensil for Pesach use in the same Mikvah that was used for immersion of utensils that are meant to be used all year round. Generally, utensils are immersed before they are used at all, thus, the Mikvah is being used all year round for vessels that are Chametz free.

Anonymous UK July 11, 2016

A new saucepan which needs tovling for Pesach - can it be immersed into a mikvah for utensils, if this mikvah is used all year round? Reply

Simcha Bart for April 8, 2016

Even though it has not been used recently, one still needs to Kasher it for Passover use. Reply

Moshe Barzev Jerusalem April 4, 2016

kashering cutlery I have a set of dairy cutlery (hametz) which hasn't been used for several years (3-4). Does it need to be kashered for Passover if more than a year has elapsed since last used? Reply

Richard Stasack April 18, 2015

As a retired Service Tech (for 26 years) I feel I must make some things clear. Oven cleaner can only be used on a non-self cleaning range. If used on a continuous cleaning oven it will destroy the finish. If used on a self-cleaning range it will destroy the finish. Covering the racks with is fine if openings are made between the spokes of the rack! The reason for this is that if the racks are wrapped with foil you create a thermal barrier between the burner and thermostat sensor. I helped many of my Jewish customers keep dairy and meat separate in dishwashers by making the upper easily removable. This way they only had to purchase new upper and lower racks and keep them separate. Also I advised them to run one cycle with new racks and no dishes to flush out any possible contamination. Reply

Paul Chicago April 7, 2015

Kashering Corningware Pyroceram I have found the secret to a more happy Passover kitchen is using Corningware for cooking, baking, roasting and food storage -- one MUST only use the 'pyroceram' versions (Including Corningware 'Stovetop' and Visions cookware), and NOT the cheaper plain stoneware versions, and definitely NOT Pyrex. The Pyroceram versions are a type of glass-ceramic material that can withstand extreme temperatures and can be placed into a self-cleaning oven cycle. Scrub them thoroughly of food residue until squeaky clean, then carefully place onto oven floor or lean against oven walls. Then run the self clean cycle. The intense heat will kasher the items, just as it kashers the oven and the oven's 'glass'-window. Wash off any remaining residue (ash). It works well and it does not harm the Pyroceram items in the least. I have done it multiple times and it works well. Just scrub them well before doing it. (Do NOT do this with any other items like Pyrex or stoneware! -- they can crack.). Reply

Yael April 6, 2017
in response to Paul:

My understanding is that corningware and the like are considered colored glass which, unfortunately, cannot be kashered. Reply

Shaul Wolf Brooklyn March 3, 2014

Kashering from Fleishig to Pareve In general, the same guidelines apply. The oven should be thoroughly cleaned, and should be left to sit for twenty four hours.
There is one leniency however, and that is that there is never a need to blowtorch the oven. Such a stringent custom is only relevant when the oven was previously used for non-kosher foods, and not when one kashers from meat or milk.

It should be noted, that one should not (constantly) kasher his oven or his dishes from milk to meat. The Rabbis forbade this, because the chances of forgetting or making a mistake are very high. To change from meat or milk to Pareve, however, is permissible. Reply

Anonymous Waltham March 2, 2014

From kosher fleishik to parve Are there any specifics in switching (koshering) the oven after it was used for meat cooking to baking the parve bread? Is it the same as the regular koshering described above?

Thanks Reply

Anonymous Florida January 27, 2014

Purchase new Shabbat electric oven We have only had gas ovens. Our new home will be electric only what brand will allow heating/warming in an electric oven on Shabbat?
Thank you Reply

Menachem Posner Montreal July 26, 2013

To Shana A rabbi does not need to come to the home to make a blessing. However, if this is your first time koshering a home, I would suggest that he come over to make sure that everything is done according to halacha. About your dishwasher, it may not be sufficient for many dishes. Again, this is one of those things that having an on-site rabbi would be helpful for.

Mazal tov on your move! Reply

Shana NJ July 25, 2013

Kosherizing new kitchen I am moving into a new home and will start to become kosher. Our dishes are not kosher at this time. Can we run our utensils into a dishwasher on hot to kosherize? Does a Rabbi have to come to the home to say a bracha? Reply

Elliott Muhammad baltimore, md June 7, 2012

kosher and dairy not eaten together Why is kosher meat and dairy not eaten together? Reply

Anonymous Phoenix May 29, 2012

Kashering Full-Size Popcorn Mchn/Cotton Candy Mchn Hello,

Albeit not common or possibly regularly-used items, how does one kasher a full-size red popcorn machine? Additionally, how about a small home use or full-size cotton candy machine?

Thank you in advance of your reply.

Sample Popcorn machine information: Full-size carnival style 8-oz hot oil popcorn machine with cart. Dimensions: 59 inches tall x 27.5 inches long x 20 inches deep, Components: steel and polycarbonite, 6-ounce stainless steel kettle with built-in stirring system and kernel catcher to keep out un-popped kernels, General information: Pops up to 24 cups per batch.

Sample Home Use Cotton Candy Machine Information: 110 volts; 50 Hz; 3.3 amps; 400 watts; 2´ power cord. Dimensions: 12"L x 12"W x 11.75"H Reply

Anonymous Sydney, Australia April 21, 2012

starting a brand new kosher kitchen If everything is brand new do we need to make it kosher Reply

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