- I am curious about the use of microwave ovens for both milchig and fleishig. Is it permissible to use a microwave for both as long as they are covered and the microwave is kept clean, or is it preferable to use it for only one or the other?
- Does using a milk plate in a meat microwave with parve foot affect:
- the status of the food and
- the status of the plate
- It is possible to run your kitchen with one microwave. The preferred method of doing this is to keep the microwave clean, cover the food with plastic wrap or the like, and put a pot holder, cloth or plate under the food plate.
If the microwave is not clean, then when you heat up your food and moisture escapes (this may happen if the food is not covered, especially when liquids are being heated), it may draw the flavor of the residual food that is caked on the walls of the microwave into the food.
Technically, it is acceptable to cover either the milchig or fleishig food every time. The walls of the microwave will attain the status of the food type that is put in uncovered. When the opposite type is put in covered, steam and moisture will not escape and there is no need to worry about drawing flavor of the opposite type into the covered food. Experience has shown, however, that the food is not always covered well and moisture escapes. Therefore, it is best to keep the microwave clean and attempt to cover the food every time. If the microwave is kept clean (i.e., there is no residual food caked on the walls), then even if moisture escapes, it can only draw out flavor that has been absorbed in the walls. That will only happen if the steam escaping the “covered” food reaches yad soledes bo. The kashrus of the food can only be affected if you are certain that the microwave has been used for the opposite food type within the past 24 hours. Even then, it is unlikely that the food will become treif. I have tested numerous household microwaves and have rarely found that the temperature of walls of a microwave reach a temperature hot enough to absorb flavor. Try cooking a potato or heating a glass of water in the microwave for a few minutes and open the door and see if you can hold your hand on the sides and top of the oven for 15 seconds. If you can, then the temperature has not reached yad soledes bo. You need not be concerned that the walls of the oven have absorbed treif or dairy or meat flavor. This also is reason to be lenient on food that was placed in a microwave oven that wasn’t cleaned and the food was uncovered.
In other words, the instructions here are recommendations as to the best way to use a microwave oven in accordance with halachic considerations. However, in the event the microwave was not used in accordance with the recommended guidelines, the food will likely be kosher. Still, every situation should be evaluated on its own merit. If you are unsure, discuss your specific situation with a knowledgeable person in the area of kashrus.
In order to avoid a serious concern of kashrus (that might treif your food), something should be placed under the plate of food every time in case of spillage. There is usually a treated glass plate (sometimes revolving) on the bottom of the microwave; if that becomes dirty with milchig food and you then place fleishig on it, you could potentially have a problem when the plate gets hot. That is why I recommend always placing the plate on a cloth or a plate that is pareve or that matches the type of food being put in (fleishig for fleishig or milchig for milchig). That way, when there is spillage, it will not contact the glass plate that will be in direct contact with the container you use afterwards for the opposite type of food. For example, if you heat up a bowl of onion soup that contains cheese and some of it spills, it will fall onto the milchig plate instead of onto the glass plate. This way the glass plate remains dry of any milchig liquid. You can then place a bowl of meatballs with sauce on the glass plate without being concerned that residual milchig soup may be absorbed by the bowl of meatballs. However, in order to make sure that no fleishig gravy gets on the glass bowl, you should place a fleishig plate underneath the bowl of meatballs. This way, if there is any spillage it will not land on the glass plate either. If you are putting macaroni and cottage cheese in the microwave, it may be sufficient to place a mat or cloth under the bowl, since any cottage cheese that spills will not pass through the cloth to the glass plate. The type of material to be used should be appropriate for the type of food that you are putting in. You have to consider what would happen if something spilled.
If you use a pareve separator between the food and the glass plate, you are taking a risk. If something spills, the separator may lose its pareve status, depending on the temperature of the food that spilled and the material the separator is made of. If nothing spills and no moisture escapes the covered food, the separator remains pareve. If you use a towel or cloth and food spills on it, the separator will remain milchig or fleishig until you throw it in the washing machine. Once it is washed in hot water with detergent it reverts to its pareve status.
- It is even more preferable to have a microwave used exclusively for meat products as apparently you have. The issue arises when you use a dairy plate and parve food.
As mentioned earlier, even if the microwave is not clean, the flavor of meat cannot circulate in the oven unless the mositure reaches a temperature of yad soledes bo, which is uncommon. Test your microwave to be sure. If it does not get that hot, the plate remains dairy and the food remains parve.
If the heat level in the microwave can reach yad soledes bo and there is concern that this happened in your fleishig microwave oven (that had residual food on the walls of the oven) when parve food and a milchig plate was in there, then the food should not be eaten with dairy and the plate should be kashered if possible.
If the walls of the oven were clean of residual food and may have absorbed flavor within the walls, the plate is still kosher and dairy and the food is still parve. The absorbed fleishig flavor should be treated halachically as an eino ben yomo. Flavor from an eino ben yomo cannot negatively affect the plate or parve food.
 Provided that the moisture escaping and reaching the walls of the microwave is yad soledes bo. This will be addressed later on.
 The boiling water can kasher any absorbed flavor in the cloth since cloth, like most materials, is kasherable through hag’oloh. (Exceptions include ceramics, porcelain, china, earthenware and enamel). The general principle with regard to hag’oloh is that whatever method was used to introduce the non-kosher flavor into the vessel can be used to explete the flavor (ta’am). Once the flavor has been in the cloth for more than 24 hours, it cannot treif anything, since even if it gets into another food the flavor would be unfavorable. Nevertheless, there is a rabbinic prohibition on using a vessel even if its absorbed flavor is pagum (tainted or impaired). Using a hand towel to dry hands and dishes would not be included in the prohibition on using a vessel that has ta’am pagum (gezeiroh kedeiroh she’eino ben yomo atu ben yomo). Even using a hand towel or a dish towel as a separator in a microwave between the glass and a bowl of food is not a violation of this gezeiroh, since normally there is no contact with the food itself. Thus, there is no serious cause for concern about the absorbed food in the towel.
However, there may remain some visible particles of food enmeshed in the fibers. Hag’oloh can only kasher absorbed flavor, not food particles. For that reason, it is important to also have detergent in the washing machine in order to neutralize the entangled food. The detergent can only “kasher” the visible food; not the absorbed flavor in the fibers of the towel. Detergent will add an unpleasant, perhaps even objectionable, flavor to the food. Once it becomes inedible for an animal, it loses the status of food and thus will not be considered non-kosher.
Even when a fabric absorbs a non-kosher, fleishig or milchig flavor, it is commonly accepted that washing the fabric in a washing machine with detergent at any temperature will kasher the fabric. The logic behind this is that the detergent is pogem or taints any flavor in the towel or fabric and is absorbed even if the tool of hag’oloh was not used. So while hag’oloh will also work on fabric, it is not necessary to make sure the water is hot (yad soledes bo) when washing towels and fabrics.