Most metal pots do not allow food to heat properly and may be unsafe when used in a microwave oven, but some types of pots are compatible with microwaves. You can generally use heat-proof glass and ceramic pots, most of which will be labeled for microwave use. Some pots made of metal or other materials are specially designed for microwave ovens, and these will also be clearly labeled.
Why Most Metal Pots are Ineffective
Your microwave oven utilizes a type of radiation that passes through most materials but is absorbed by water, or the water content in foods, and bounces off of metal. Because it is deflected by metal, this radiation is less likely to come into contact with food that you have placed in a metal pot, and the food will not heat properly.
Why Some Metal Pots are Unsafe
Using a metal pot can prevent microwave radiation from being absorbed by food, and this unabsorbed energy may damage your oven. Metal in a microwave can also cause arcing, or sparks created by microwaves under certain conditions. This is especially likely if the pot you are using has metal trim or other thin metal parts. Arcing can even lead to fires in some cases.
Other Pots to Avoid
While most glass and ceramic pots will work in your microwave, there are a few types that may cause problems. Glazed ceramics may absorb some microwave energy and become very hot to the touch. Lead glaze in particular is unsafe for use with food under any circumstances. A pot of any material that has metal trim, gold paint, or other metallic parts is likely to cause arcing.
Glass, Ceramic, and Other Microwave-Safe Pots
The safest and most effective pots to use in your microwave are those that have been specifically labeled for microwave use. These may include pots made of glass, ceramic, metal, or even plastic. If none of your pots are labeled for this use, then you can safely use any heat-proof glass or ceramic pot.
Microwave Ovens and Food Safety
Michigan State University
Beware-not all food containers should be used in the microwave
Ask an Engineer
Why Can’t We Put Metal Objects in a Microwave?