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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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Discussion (23)
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.
Shaul Wolf
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?

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
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!
Menachem Posner
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?
June 7, 2012
kosher and dairy not eaten together
Why is kosher meat and dairy not eaten together?
Elliott Muhammad
baltimore, md
May 29, 2012
Kashering Full-Size Popcorn Mchn/Cotton Candy Mchn

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
April 21, 2012
starting a brand new kosher kitchen
If everything is brand new do we need to make it kosher
Sydney, Australia
April 4, 2012
Passover dishwashers
The problem with any koshering of dishwashers are the plastic components which have absorbed unkosher or meat or milk or chametz flavors in hot water, and plastic can't be koshered according to many authorities. Also, particularly in a dishwasher, it's hard to get boiling water poured over every part of the inside - according to those who allow koshering plastic -- and the normal cycle sprays hot non boiling water over only most parts. There are leniencies for people becoming kosher for the first time, and that would perhaps hold true for Passover, but you'll have to ask a rabbi who knows you and your situation.

If your dishwasher is all stainless steel on the inside, there is also more room for allowing it to be koshered.
Rabbi Zalman Nelson
Safed, Israel
March 31, 2012
Kashering for Passover
Can a dishwasher be used if you professionally raise the water temperature in the hot water heater?
Delray Beach, Flroida, US
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