Question: I am often in a situation where I would like to kasher a microwave at work or in a hotel. What is the proper way to kasher a public microwave?
Response from the OK:
A microwave works by transmitting micro radio waves through the water content of the food being heated. As the agitation increases, the food generates heat. Once the food gets hot, it heats up the container and the entire chamber fills up with steam. Therefore, it would seem to be relatively simple to kasher.
Just as the non-kosher food contaminated the microwave through its steam, the microwave can be kashered by filling the chamber with steam. The microwave must be clean of all food spills and splatters. One possible problem is that there can be food stuck in the vent (especially problematic if the vent is on the ceiling of the microwave where food can drip down), which is almost impossible to clean.
In addition, the microwave window is made of glass and some poskim do not permit kashering glass, but others are more lenient and permit kashering glass year round (but not for Pesach). In addition, the inner chamber is made from aluminum with a coating of plastic. Some poskim state that it cannot be kashered, but others do permit kashering.
In conclusion, it is preferable not to kasher a microwave from treif to kosher and food should be double wrapped before microwaving. If one must kasher a treif microwave, it should be done in the following manner:
1. Clean the microwave and spray the vent with cleaning solution.
2. It is preferable to clean the rubber gasket and outside as well.
3. If possible, remove glass tray and kasher it with boiling water. Allow microwave to sit idle for 24 hours.
4. Fill a Styrofoam cup with water and microwave for at least 10 minutes.
5. Move the cup to a new spot and repeat step 4 to kashe the place where the cup stood.
L’chatchila (in the first place), it is not a problem to kasher between kosher meat and kosher dairy, but it should not be done as a method to routinely use the microwave for both.
Originally published in the KosherSpirit.com
it was recommended to use styrofoam for kashering purpose not for eating/drinking
The search engines list the composition of styrofoam as polystyrene, benzene and/or pine tree resin. if #7 has a source for tallow being included, could he please let us know. The fact that styro is made from up to 3 ingredients that may cause various illnesses sure does not make me happy. I’vebeen avoiding it for years,especially for hot things. The scary news, mentioned in a star-k article THE STORY BEHIND KOSHER PLASTICS, is not only that many ingredients in plastic materials can migrate into food, but that manufacturers a presently testing ways of making plastics like that on purpose,… Read more »
I would assume that it is not possible to completely double wrap food in a microwave. The issue is that the package could explode if it is sealed. The vapors in wrapped food have nowhere to escape.
It is not true. The cup will not melt.
Experience taught me that it is hard to steam up the microwave
because the fan vents the vapors out.
To overcome that I first bring the water to a boil, then shut the
microwave with the cups inside for a while.
That steams up the inside.!!
The earlier Lubavitcher Rabbonim insisted on eeruy to kasher them, stating that there is no halachic president for
kashering with steam. Who changed that , and on what basis?
how can we use it for hot drinks if its made from beef fat i think win styrofoam cups are not made from beef fat
Styrofoam is made with tallow (a form of beef fat). When heated, the meat by-product is released. It is unlikely that the beef used in Styrofoam is Lubavitch Shchita!
Do not put strofoam plastic with your food in microwave oven
The chemicals from the plastic or the styrofoam will leach in to your foods,and might be a cause of many illnesses,may we be protected from.
Always use only glass ,ceramic of paper
another lubavitch article publishing another chumra filled psak….
… I would just stick with cold food rather than try to kasher a microwave that has obviously been used for treifes.
I have two microwaves in my house (milchig & fleishig) and it is pretty much impossible to get the interior surfaces completely clean, especially at the seams and in the vents. Since I have many demands on my time, I’ve given up trying to get them perfectly clean. I don’t use them for Pesach anyway, so it really doesn’t matter if somewhere a pinpoint-sized piece of something is stuck.
My $0.02.
The article says to use a styrofoam cup. Do not put Styrofoam in the microwave for more than a minute, it will melt.
I was told to put my food in two ziploc bags and warm up like that. When the outer bag looks like it is going to pop, I stop the microwave, let out the air and close it up again and heat it up more if needed. I work in a very large office building and since they will not let me have my own microwave and it is not possible to kashur one everyday, this is what I was told to to.
A small point. In this order the author mentions and highlights the importance of cleaning the showers of food from the walls, etc… Yet, the method supposedly being used to kasher the oven is steam and I quote: ” Just as the non-kosher food contaminated the microwave through its steam, the microwave can be kashered by filling the chamber with steam. The microwave must be clean of all food spills and splatters.” Yet those areas which had food splatters, would seem to need a koshering with hot water, not just steam. And in the lifetime of a microwave, food splatter… Read more »