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

1. The oven should not be used for twenty-four hours prior to kashering.
2. Spray all internal surfaces of the oven with a chemical cleanser to remove all surface dirt.
3. Disassemble the inner parts of the oven: remove grates, the shelf separating the oven from broiler, remove the entire broiler and its drawer.
4. 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.
5. Reassemble the oven. Set the oven dial at top heat (broil) for 1« hours. Unless the broiler tray is blowtorched (or heated in a self cleaning oven cycle) 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.
6. Some have the custom of blowtorching the interior surfaces of the oven in order to assure the removal of any remaining dirt.

Self-Cleaning
Self-cleaning ovens are self kashering. Kasher the oven automatically by putting it through one full cleaning cycle, (approximately 3 hours). Don’t forget to clean the top cooking area, as indicated below.

Gas Range Tops

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

Electric Stove Top
Follow the above cleansing procedures. Set the electric burners on the highest setting until they glow red after a few minutes.

There are various customs with respect to cooking milk and meat dishes in the same oven. Some people only cook meat in their ovens, and have small toaster ovens for milk dishes.
A second custom is to wait 24 hours between the cooking of milk and meat. The most lenient custom is to wait until the oven has cooled between the cooking of milk and meat. If the milk or meat is tightly covered (e.g. aluminum foil) it is not necessary to wait. If there is any spillage of meat, the oven may not be used for milk before it is cleaned thoroughly and set at top heat, and vice versa. It is wise to line the oven bottom and check the broiler for any spillage before cooking.

Microwave
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.

Silverware made of one piece of metal can be kashered. However, any utensils with a plastic, wood, or bone handle which will be damaged by boiling water cannot be kashered. If the plastic, wood or bone will not be damaged and can be cleaned properly. it may be kashered, employing the following procedure. Clean the utensils thoroughly of food and rust (especially at the joints). Wait 24 hours. Kasher the silverware by dropping them, one by one, into a vat of boiling water. Make sure that:

1. The water is actually boiling when you place the silverware in the vat (Remember, that placing the utensils in the vat often lowers the temperature of the water below the boiling point).
2. Large utensils may be purged in the water, one side at a time. But make certain that the part that you are immersing is completely surrounded by water.
3. Remove the utensil and rinse in tap water. Use tongs or place a soft wire basket into the pot to help with removal.

1. Metal (not enamel or teflon) pots and pans not used for frying, which can be thoroughly cleaned, can be kashered by the boiling method described above. If there is accumulated dirt under plastic pot handles, they must be removed before kashering.
2. Frying and baking pots and pans can be kashered by slowly and deliberately glowing the utensil with a blowtorch,by placing them in a self-cleaning oven during a full cleaning cycle (not advised). It is usually very difficult to kasher them correctly. If possible, replace these utensils with new ones.

A sink made of metal can be kashered by rinsing every square inch of the sink with boiling water (the water must be boiling right before you pour it.) Porcelain sinks cannot be kashered. In both instances it is wise to purchase plastic sink tubs, one for milk dishes and one for meat dishes.

Counters made of nonporous material can be kashered. (Anything porous like butcher-block counter must be sanded down and then kashered.) Simply follow the procedure applicable to sinks. It is preferable not to place hot utensils directly on the counters.

China, earthenware, porcelain, corningware, corrella, pyrex, duralex enamel, glazed stoneware, may be kashered only by reglazing in a kiln at 900 F for one minute, or in a self-cleaning oven for an entire cycle. Extreme caution should be exercised since very delicate items may not be able to withstand the intense heat. Valuable porcelain dishes which were not used for one year, may, in consultation with your rabbi, be kashered by dipping in boiling water 3 times.
Glassware used for cold, or for tea and coffee may be kashered by soaking in room temperature water for 72 hours, changing the water every 24 hours.

A refrigerator may be made kosher by thoroughly cleaning with soap and water.