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Jewish Recipes --> Kosher Kitchen Ware -- Definitions Blech

1: Blech - literally means metal.  It refers to the metal cover plate that is placed on an open flame in order to cover it on Shabbos.

2: Cooking

Heating any uncooked or partially cooked solid or liquid food to a Temperature of 113 degrees F, Yad Soledet Bo, or higher is termed "Cooking"

3: Ein Bishul Achar Bishul - "There is no cooking after cooking/"  Fully cooked solids are not able be cooked again.  However, liquids can cook again and may not be reheated.

4: K'deirah Al Gavy K'deirah - a vessel on top of another vessel, e.g.. a pot containing food on top of another pot containing food.

5: Yad Soledet Bo - Laterally means, "a hand can be placed on it".  That is, if you can put your hand on a heat source without burning you hand, you may use that as warming tray or blech because no cooking will occur.  This temperature is generally agreed to be 113 degrees F.

Halaching Principles Related to Warning Foods

1: Cooking as, defined above, is not permitted on Shabbos.  Placing fully cooked foods directly over a flame, or any source of heat that can be used for the purpose of cooking is forbidden.

a: "Putting food onto a flame resembles cooking and may lead to actual cooking."  This is related to the principles of N'Shinah L' Chatchilah.

b: Placing full cooked foods onto a source of heat in a way that resembles cooking is not permitted.

c: Melting fat, or heating cool liquids [even if previously boiled] by placing them on source of heat, is forbidden, even if a K'deirah is used.

d: Food may kept on a stovetop if the flame is covered.  Covering the flame indicates that you are not concerned with adjusting the flame.  Therefore, some authorities also require that the knobs be covered or removed for the same reason.

2: Returning food to a blech.
Foods may not returned to a blech unless the following conditions are met:

a: The food is fully cooked before Shabbos.

b: The food must still be warm at the time of returning it.

c: The pot must still be in your hand, i.e., it was not released from your grip.

d: Your intention was to return the pot to the blech before you removed it.

3: Foods that have cooled down

a: may be placed near [not directly on] a source of heat, to remove the chill, if there is no possibility of it reaching Yad Soledet Bo 133 degrees F. Or, unless, a K'deirah is used.

4: Foods may be returned only to the areas of stand blech where the surface temperature is cooler than Yad Soledet Bo, 113 degrees F.  This bearly warm to the touch.


The Un-Blech is both hotter and colder than a standard blech. To make sure that your food gets hot use short wide dishes like a casserole to warm foods.

Use a crockpot for chulent.

The entire surface is permitted for use.

Drain the fat from the meat or chicken that you intend to rewarm on Shabbos before Shabbos, so the problem of melting fat is not an issue.

Bake or broiled foods may be rewarmed on Shabbos.

Food like rice which are boiled, raise questions. Some feel that they may not be reqarmed others do not see a problem since the Un-Blech can not be used to cook foods. Ask your Rov.

Food can be left on the Un-Blech for long periods of time in short wide dishes. the temp of the food must be at leat 125 degrees to prevent spoilage. If your Rov is not familiar with the Un'Blech, it is best to bring it to him when you ask your questions. As your Rov about warming specific goods.The k"deirah is, to mu knowlege, the only new blech that has been examined by Rabbinic authorities.

A partial list follows: Rav Dovid Feinstein, Rav Herschel Schecter of YU, Rav Kenneth Auman of Young Israel of Flatbush, Rav Dovid Cohen.


First time users - note--before using your Un-Blech for the first time you should calibrate the burner that you intend to use with the K'deirah.

This should be done during the week so you can get the best setting for you range. This is a most important step. Too high a flame will cause the water to boil out before the end of Shabbos.

1. Bring about 6-8 cups of water to a boil in a pot or use instant hot from the sink.

2. Remove the teakettle from the burner and reduce the flame so that it is about 1/4 inch high. (On many ranges this will conform to the first detent or click that you feel as you turn the knobs to adjust the flame.)

a. Electric ranges work perfectly well with a K'deirah Blech. However, since electric coils are much hotter the a gas flame, adjust the temperature so the

the coils do not glow red hot. Red hot coils can melt aluminum pots if they are empty. If the water boils out and the coils are glowing the lower compartment will melt or lose its shape. This will damage the base tray.

3. Place the tray of the K'deirah Blech onto the burner.

4. Pour in the hot water.

5. Place the cover onto the K;deirah

6. After an hour or so check the Un-Blech. If you see steam escaping, your setting is too high, lower the flame a little and repeat the above procedure. Check the tem0erture of the surface, it should be very hot.

When you think that you have the correct setting leave the K'deirah on for the night. In the morning check the temperature of the surface again.

Note: you may hear a low sizzling noise coming form the K'deirah Blech. This is normal. If you hear a rapid sizzling sound, your flame may be too high. Adjust the flame until the sound is softer.

7. Mark the control knob with a pencil and turn off the flame. After a few minutes remove the top and check the water level. If you have about as much water as you started with mark the control knob permanently using a marker. You are ready for Shabbos.


1. Light only only burner on the stovetop. first time users see note above.

2. Adjust the flame to the calibration mark that you made previously. See not for first time users above.

3. Place the K'deirah Blech base tray on the stove top.

4. Pour 6-8 cups of water into the base container and over it. Hint- boil water in your teapot and use the hot water to set up the K'deirah Un-Blech. It will be hot immediately.

Drain off all excess fat and oil from the meat that you intend to reheat. It is best to clean the pot to remove all of the excess liquid.

Liquids that are on the blech before Shabbos may remain on the blech. (See halacha)

Cholent can spoil on a k'deirah because the surface is not hot enough to maintain a cooking temperature. Do not attempt to finish cooking your chulent on the Un'Blech. Use a crock pot for chulent. Remember a chulent, or casserole, contains free liquid. It may not be replaced onto any blech once it has cooled down.

Some rabbonim only allow the rearming foods that were roasted or broiled not boiled. Others do not make this distinction on the Un-Blech.


1. The K'deirah Blech's large flat evenly heated surface is ideally suited for placing a number of tins, dishes or pots anywhere on the surface. There are no restricted areas. To heat your food efficiently and quickly it is best to use flat wide tins or pots. Casserole pots are the ideal shape, but don't forget to allow enough time for both the pot and then the food to hear up. Because the K'deirah Blech and relax for an hour to get a wonderful hot meal.
2. Solids may be rewarmed on the K'deirah Blech
3. Liquids may not be replaced onto the K'deirah Blech once they have cooled.

After Shabbos

1) Shut off the flame
2) Wait until you can touch the surface without burning yourself.
3) Allow the Un-Blech to cool down remove the water
a) Get a small wide mouthed container or dish to use as a scoop.
b) Or, use a siphon
c) Note-If you have a very steady hand, like my wife, you can move the entire base container without scooping out any of the water.

5) Dry the K'deirah Blech before storing it.

The most important thing to keep in mind when you use K'deirah Blech is that it is hotter than a conventional blech over the entire surface except one area. A conventional blech is cool to touch at the end furthest away from the fire, but extremely hot right above the fire. There is no hot spot on the K'deirah Blech. this fact has most profound affect on you Shabbos meal.

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Sept 2005 - 2013 - Kosher Recipes - Kosher Cooking - Jewish Cooking - Jewish Recipes - Jewish Foods