According to Rav Moshe, Pyrex, Duralex and Corningware cannot be kashered. Others permit the kashering of Pyrex and other heat-resistant glass utensils by the process of hagalah if used for hot food and by miluimVeirui if used for cold food. According to Rav Moshe, dishwashers that are lined with plastic walls cannot be kashered.
Other opinions hold that a plastic-lined dishwasher can be kashered in the following way: First it must be thoroughly scrubbed. Then it should not be used for 24 hours. Then the dishwasher should be turned on to allow boiling water to spray inside. Dishwashers lined with porcelain or enamel cannot be kashered. Gas or electric ovens can be kashered by libun and according to some poskim even by libun kal. According to Rav Moshe, such ovens can be kashered by running them through the self-cleaning cycle.
Microwave ovens can be kashered. They should be thoroughly cleaned and not used for 24 hours. Then a bowl of water should be placed inside. The microwave should then be turned on until the inside is filled with steam.
Mixers used for mixing dough or other chametz can generally not be kashered because it is almost impossible to remove the chametz particles trapped in the machine. Blenders that can be dismantled should be thoroughly cleaned and their metal parts and bowls immersed in boiling water. Coffee percolators, to the extent that they can be thoroughly cleaned of all chametz particles, can be kashered by boiling water inside them. Rabbi Shimon Eider, however, writes that they should not be kashered because it is impossible to clean out all chametz particles.
According to most opinions, whisky glasses cannot be kashered because they retain the smell and flavor of whisky. The Aruch Hashulchan rules that they can be kashered by milui and irui. In view of the fact that there are so many conflicting opinions in this area of halacha, it is advisable to consult a rabbi when in doubt.
