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KASHERING A KITCHEN
Rabbi Marc Boone Fitzerman

Introduction

Of the norms that define Jewish ritual life, kashrut occupies a position of central importance. The notes below are designed to enable newcomers and veterans to feel at home in this system, without undue anxiety. Setting up a kosher kitchen is not particularly taxing. Nor is it prohibitively expensive. Anyone who wants to set up a kosher kitchen can convert an existing kitchen by simply following these directions.  They can also serve as a reference sheet of remedies.  A dairy pot inadvertently used for preparing a meat dish can be re-kashered as often as such accidents occur.  Finally, a kosher kitchen can be converted to Passover use by following the same set of guidelines.  No Virginia, you do not need four sets of pots, pans, cooking utensils, and silverware.  Two will do nicely.  Take heart, as we begin with the basic standards of the halacha (Jewish law).

The Stove

Scour all surfaces carefully, inside and out.  Take care to remove all baked-on drips and spatters and then place each range-head on its highest setting.  An electric burner is kasher as soon as it glows red.  Gas burners should be left on until the metal trivet which supports the pot becomes hot enough to singe a piece of paper.

The Oven

The oven itself is now kashered in a similar way. Whether electric or gas, the oven should be set at the highest temperature which will cause every burner to ignite or (if the oven is electric) every coil to glow. The “broil” setting is inappropriate for this purpose because it involves only a single set of burners or coils.  Leave the oven at this setting for no less than half an hour and no more than an hour.  The oven is then kosher and can be used to prepare both meat and dairy foods.  The only restriction is that meat and dairy foods cannot be placed in the oven simultaneously. Covered pots containing meat or dairy dishes may, however, be simmered simultaneously on the range.  (Note: self-cleaning ovens can be kashered simply by running the unit through its self-cleaning cycle.)

Toaster and Convection Ovens

Kasher these appliances as you would any other oven. Clean thoroughly and then set the oven at its highest temperature for no less than half an hour.

Microwave Ovens

Clean all surfaces carefully, removing drips and spatters.  If the oven has a glass shelf to support cooking utensils, remove the shelf, and immerse it in boiling water as you would a pot requiring kashering (see next item).  Alternatively, the glass panel may be left to soak in a tub of water for 72 hours, changing the water every 24 hours.  For a plastic shelf, the rule is the same, with one exception.  If the panel will not withstand boiling, it must be replaced, not soaked.

A Styrofoam cup of water is now placed in the microwave, and brought to a boil.  (If there is an already kashered or new glass utensil, that, too, may be used.)  Once the chamber of the oven has been thoroughly steamed by the boiling water, it is kosher.  (Just a few minutes of steaming is sufficient.)

The Refrigerator

No special efforts are required.  Simply wipe out thoroughly and sponge each surface clean.

Kettles, Stock Pots, Soup Pots, and Sauce Pans

This category includes all steep sided vessels which are generally used to heat or boil liquids.  Regardless of type (enamel, Teflon, T-fal, or Silverstone-coated; stainless steel or aluminum; copper or copper clad; wooden, hard plastic, or metal-handled, Corningware) all are kashered as follows:

1. Scrub and scour each pot in the set so that no grime remains anywhere on the pot or lid.  (The rules which apply to pots apply equally to their lids.)

2. Before going further, give the pots, at minimum, a twenty-four hour rest.  Set them aside and do no cooking.

3. The following day begin with the largest pot in the set and fill it to the brim with water. Bring the pot to a rolling boil.  At this point water must be forced over the sides of the pot so that the outside surfaces are kashered as well. A hot stone or piece of metal is traditionally used for this purpose, but another good solution is the smallest pot in the set.  Set this on the range and bring it to the point where it will sizzle on a drop of water.  Then bounce this pot on the surface of the water that has already come to a boil in the larger kettle.  The bouncing action will force a cascade of water over the sides of the larger pot.  Make sure that the same water covers the handles or use a bubbling tea kettle for the same purpose.  Now empty the pot and rinse it with cold water.  The largest pot is now kosher.

4. Proceed now to kasher all the other pots in the set.  Water is once again brought to a boil in the largest pot.  One after another, the other pots and lids are immersed in the boiling water. Note that a cold pot will probably cause the water to stop bubbling momentarily.  Immerse each pot long enough so that the water comes to a rolling boil once again.  Once this happens, the pot can be rinsed in cold water and designated either meat or dairy.  Remember also to immerse every part of the pot, including the lid.  This may take some maneuvering as you immerse one part of the pot and then the other.  But it does not affect the quality of your kashering.  If there is no pot large enough to easily accommodate any other pot in the set, a kashering session in the synagogue can be easily arranged.

Glasses, Dishes, Mugs or Cups, Serving Pieces. Storage Containers, and Mixing Bowls Made of Glass

Glass utensils of any color used for every purpose other than baking or boiling may be kashered in one of two ways: boiling or soaking.  If boiled, they should be cleaned and set aside for twenty-four hours.  Once this is complete, they should be immersed in a large kettle of boiling water for a moment or two and then rinsed in cold water.  The same special notes that apply to silverware apply to glass (see below). 

If soaked, they should be placed directly in a large metal or plastic tub that is not used for cooking.  (A bathtub that will retain water reliably is perfect.)  Cover the dishes with water of any temperature and change the water at 24-hour intervals for a total of seventy-two hours. Rinse and designate as meat or dairy. 

Although some people use glass utensils interchangeably for meat and dairy meals (provided that the foods or liquids they contain are cold), this practice should be avoided.  To take one common example, there should be a set of drinking glasses for dairy meals and another set for meat meals, even if they will only be used for cold beverages.  Still, there is some room for leniency in the law pertaining to glass utensils.  If you cannot afford two sets of drinking glasses (or a second set of plates when one is made of glass) please speak with Rabbi Fitzerman who would be glad to offer advice.

Tea Kettles and Double Boilers Made of Glass

Since these utensils are used to prepare hot foods over a burner or flame, they should be boiled.  Treat them exactly as you would a pot that needs to be kashered (see above). Make sure that the hard plastic handle can tolerate the heat of boiling water.  If not, the utensil will have to be replaced.

Metal, Pyrex, or Corningware-Style Baking Pans

All such utensils may be kashered on one of two ways.  The simplest method is to scour them clean and treat them as you would any sauce pot that needs to be kashered by boiling (see above).  Alternatively, they may be cleaned and then placed in an oven set at 500` and baked for an hour.  Metal baking pans, because they are impervious to flame, may be kashered in one other way.  As with frying pans, a propane torch may be used to play a flame over the utensil until every surface has been heated.  See the section on frying pans above for details.  It is crucial that all such pans are thoroughly cleaned before kashering. An electric drill fitted with a wire brush may be very useful here.

Plastic Storage Containers

These items make up part of the small category of good that cannot easily be kashered.  You may try to boil them, but relatively few of them will stand up to the heat of boiling without melting or distortion.  Replace them with containers in two different patterns or colors, one for meat and one for dairy.  Containers used only to store cold, dry foodstuffs (such as pasta, beans, nuts and the like) should simply be rinsed.  Once they are used for hot or moist meat or dairy foods, they become meat or dairy and you may not be able to kasher them successfully.

Utensils Used for Cooking and Preparing Food

This category includes everything from slotted spoons and spatulas to egg slicers and melon ballers.  All-metal utensils that are used (even occasionally) with hot foods should be treated exactly as silverware.  The same is true of utensils that are all-plastic or wood or those with plastic or wooden handles.  As long as they can withstand the heat of boiling they may be effectively kashered.  Utensils such as melon ballers that are used only with cold foods are no problem at all.  Even if they are made entirely of wood or plastic, they may simply be rinsed and set aside.  One important note: every kitchen should have a complete set of meat and dairy cooking and food-preparing utensils.  However, items which come into contact with pareve (neutral) foods only need not be duplicated.  One egg slicer will suffice.

Unglazed Clay Casseroles and Baking Dishes

These items, sold under such names as “Romertopf” and “Schlemmertopf,” are made of a highly absorbent ceramic material.  In fact, they are designed to sponge up liquids that are slowly released in the course of cooking.  Because of this absorbent quality they, too, are part of the small category of items that cannot be kashered.

Knives

Knives which are used only for cold foods may be purified by plunging them into hard earth ten times.  The abrasive quality of the soil cleans the surface of the knife of any accumulated grease or residue.  If the knife is to be used, even occasionally, with hot foods (or if the idea of plunging an expensive knife into the ground makes you nervous), one of two other techniques should be used.  Treat the knife as you would a pot in need of purification and subject it to boiling (see above).  Alternatively, the knife may be subjected to direct heat until part of its blade begins to glow or a piece of paper brought into contact with it will be singed.  This second method is preferable, but boiling suffices. 

One important note: unlike almost every other article in the kitchen, knives cannot normally be purified for Passover.  The area where the blade meets the handle is not susceptible to the kind of cleaning which Passover necessitates.  Two inexpensive sets should therefore be purchased especially for the holiday.

Platters and Serving Pieces Used for Cold, Dry Foods

Containers used for cold, dry foods only may be simply rinsed and designated meat or dairy.  This applies to every platter, serving dish, or container, regardless of the material with which it is made.

Stainless Steel Sinks

Another simple matter.  Stainless steels sinks should be thoroughly scrubbed and doused with boiling water poured from the container in which it was boiled.  Make sure to cover every surface of the sink.

Frying Pans, Broiling Pans and Racks, Barbecue Grills and Spits

This category includes all utensils, of whatever material, designed to cook foods under or over a direct flame or source of intense heat, and which are not regularly used to boil broths or other liquids.  Like the pots described in the pre- ceding section, these utensils should first be thoroughly scoured free of any accumulated grease or staining and set aside for 24 hours.  An electric drill fitted with a wire brush is sometimes helpful in achieving a perfectly clean surface. 

As soon as this waiting period is complete, the utensil in question may be “glowed” in a number of ways. It may be placed over a burner or glowing coal, or under a broiler until it become red hot.  Alternatively, it can be heated in any one of these ways until a piece of paper is singed when brought in contact with it.  Finally a propane torch may be used to play a flame over the utensil until every surface has been heated, however briefly.  The torch should be adjusted so that it produces its most intense heat. 

When this process is complete, any part of the utensil (such as the handle or the lid) which did not reach the same temperature as the part directly over the fire, should be immersed in boiling water as if it were a pot used for boiling (see above).  The utensil should now be rinsed in cold water and set aside for meat or dairy use.

Silverware

All-metal silverware (serving spoons and forks included) can be kashered quite simply by boiling.  Begin by scouring each piece and setting aside the whole set for twenty-four hours.  On the following day, bring a large pot of water to a rolling boil.  (The same pot used to kasher smaller pots may be kept boiling for this purpose.)  Proceed by immersing each piece of silverware in the boiling water for a moment or two and then rinse in cold water. 

Two important notes:

1. Many pieces of silverware can be immersed simultaneously.  At no time, however, should the volume of silverware make up more than 1/60th of the total volume of boiling water.

2. As in the case with pots, cold silverware dropped into a pot of boiling water is likely to lower the temperature to a point where boiling ceases.  Do not remove the silverware until the boiling resume sand the silverware has spent a minute or two in boiling water.

All of the above applies equally to metal silverware with hard plastic or ceramic handles.  As long as the handles will withstand the heat of boiling without melting or discoloration, they may be kashered.

Electric Coffeemakers

These appliances, used for nothing but brewing coffee, do not need to be kashered.  If there is any possibility that some utensil used for another purpose came into contact with hot coffee or water while it was contained in the coffee-maker, the appliance should be activated and “cycled through” on plain water. The coffeemaker is then kasher.

Electrical Appliances

The rule of thumb is that every small appliance that comes into contact with hot food must be either (1) “glowed” or (2) immersed in boiling water, inside and out.  The first category consists of electric woks, frying pans and the like.  Since these appliances are used to fry, rather than boil liquids, they should be thoroughly cleaned and then allowed to reach a level of heat at least sufficient to singe paper. 

The second category consists of electrical appliances that are used to boil liquids or which may come into contact with boiling liquids, but are not used for frying.  All parts of the appliance which come into contact with food must be treated like a sauce pot and fully immersed in boiling water (see above).  If these sections are not detachable from the motor or heat source which give the appliance its special value, the whole may have to be replaced.  Motors and electrical fittings are not normally immersible. 

Finally, electrical appliances which are used solely to prepare cold foods may simply be rinsed.  To take just one example, a cake mixer in need of kashering should first be thoroughly cleaned.  If it is only used for cold ingredients, the beaters and bowl should be detached and rinsed.  Not attention need be paid to the body of the appliance, since it does not normally come in contact with the food.  If, however, the mixer is even occasionally used to prepare hot ingredients (chocolate, say, warmed in the microwave or on the range), the beaters should be detached and subjected to immersion (see above).  If the bowl is metal, it should be similarly treated.  If the bowl is glass, it may be either immersed in boiling water or soaked for three days, with a change of water every 24 hours (see above).  Once again, no special attention, aside from cleaning nooks and crevices of accumulated dirt, need be paid to the body of the mixer itself.

Fine China

Fine china, a hard white ceramic material fluxed with bone ash and translucent when thin, occupies a special place in the law pertaining to utensils made of clay. Because of its special qualities, and because of the expense generally involved in acquiring it, the law is lenient in allowing it to be purified.  The procedure is to simply set it aside for one complete year, after which it may be rinsed and then designated as meat or dairy, and used without further concern.  I would not hesitate to extend this provision to so-called “restaurant china,” ware which is fired at slightly lower temperatures and heavier in feel and appearance.

Glazed Earthenware, Stoneware, and Porcelain

According to every source on the subject of kashrut, these articles can never be purified.  This view may reflect a misunderstanding concerning the essential properties of clay bodies and glazes when fired to extremely high temperatures. I personally believe that they should be treated exactly like fine china, although this would be considered a radical, minority view.

Raku Pottery

Because of the special procedures used in forming and glazing these vessels, they are porous even after firing. Truly, these are vessels which cannot, under any circumstances, be purified.

Countertops and Tables

Formica and wooden surfaces should be thoroughly scoured and doused with boiling water poured from the pot in which it was boiled.  Although some people take the extra step of covering such surfaces with contact paper, plastic or foil on Passover, this is not, strictly speaking, necessary.

Cupboards, Drawers, and Racks

Cupboards in which dishes and utensils are stored need no special attention beyond routine cleaning.

Dishwashers

Dishwashers should be “cycled through” using clear water. They may then be used for meat or dairy dishes, but not both simultaneously.  Run each set separately and separate between meat and dairy washings with an “empty” rinse cycle.  Two sets of racks are not necessary.

A Note on Washing Dishes by Hand

One of the underlying principles concerning the kashrut of utensils is that ritual impurity is communicated in the presence of heat and moisture.  Since dishwashing is most often accomplished by means of hot water soaking and rinsing, meat and dairy dishes should be not washed together. The easiest thing to do is to set aside one sink for meat and the other for dairy and to use separate sponges and scrub brushes for each set of utensils.  Most observant families also use separate drainboards and dishtowels, but these are not absolutely necessary.

Some General Principles

Many items in a kitchen can be made kasher in a number of different ways.

Something like glassware that could be soaked for three days, could also be boiled in order to make it kasher. Similarly, something that calls for boiling could also be made kasher by running over it with a torch. The hierarchy of techniques, running from least to most powerful is:

Soaking

Boiling

Torching

In other words, if an item calls for soaking, it might be more expeditious to boil it, particularly when you are pressed for time. However, if it calls for torching to begin with (e.g. a pan used for frying), it must be torched and cannot be boiled or soaked. You can move up the hierarchy and use a more powerful technique when it is not, strictly speaking, necessary, but you can’t go back down the ladder and use the less powerful technique to begin with.

A Note on Burying

In the folk religion of the Jewish People, utensils that have been made treif are re-kashered by burying them. In actuality, burying plays no role in the “official” body of rules and regulations of kashrut. Writers on the subject speculate that the use of earth as an abrasive for cleaning knives led to this fundamental misunderstanding and a long-time habit of burying utensils for the purpose of kashering them. The custom of burying continues to be observed and may have its supporters among official poskim (deciders of Jewish law). However, we do not recommend kashering any utensil in this way.

A Note about Using the Mikveh

Another widely-held idea about kashering utensils is that this process is accomplished by dipping utensils in a mikveh (Jewish ritual bath). This conception arises from the fact that new utensils which have never been used before and come straight from the store or manufacturer  are indeed immersed in the mikveh before they are used for the first time. This “commissioning” process is called “toiveling,” a Yiddish derived word from the Hebrew term for immersion. At the Synagogue, all utensils used for the first time are indeed processed this way, and members of the community are invited to toivel their dishes and utensils before using them. This is not, however, a strict necessity and dishes would still be considered kasher if they had not first been toiveled. However, toiveling plays no role in kashering dishes or utensils (either at home or at the Synagogue) that have been made treif.  Neither does the mikveh play a role in readying dishes or utensils for Passover.