Why is some metal safe to use in a microwave, but others not?
This might be a more scientific question, but it relates to cooking and I thought it was interesting.
I just made my lunch which was a microwavable bowl of chunky soup.
The directions said:
Remove metal lid, remaining metal rim is microwavable.
How can this be?
Best Answer
Metal on its own doesn't necessarily cause electric discharge in a microwave.
What causes the sparking that you see when you put a fork in a microwave is due to the "sharp" edges of the fork. These edges concentrate the voltage at their tips which will cause a spark when it exceeds the dielectric breakdown of air.
Things like sheet pans (with rounded edges), or rounded metal racks are used frequently in microwaves with no ill effect. The absence of any pointed edges allows this. The rim of your bowl fits this requirement.
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Quick Answer about "Why is some metal safe to use in a microwave, but others not?"
Not all metal is safe in the microwave Metal is not safe in the microwave if: There are multiple pieces of metal next to each other (like the tines of a fork) The metal has an extremely thin or sharp edge (aluminum foil, gold trim on tea cups or plates)Why is some metal microwave safe?
The microwaves will not penetrate the metal; they can, however, induce an electric current in the bowl which is likely to have no consequence unless the metal has jagged edges or points. Then "arcing" can occur and sparks will fly. If there is something combustible in the oven, a fire is possible.Why are some materials microwave safe while others are not?
There are many plastic containers that are microwavable, which complicates the whole situation. Many plastics contain chemicals similar to polystyrene and can be very bad for you if used improperly. When heated, these chemicals leach from the container into the food you're cooking.Are there any metals that are microwave safe?
The USDA has a list of safe and unsafe containers for microwaving, as well as guidelines for cooking safely. You can use materials like aluminum foil safely in small quantities as long as your owner's manual gives the blessing. Make sure the foil is new and smooth, not crumpled.More answers regarding why is some metal safe to use in a microwave, but others not?
Answer 2
I think it also has to do with arcing. If the metal is close enough to other metal that electricity can leap the gap, it'll spark. I once stuck a metal bowl--very round on the bottom--into a microwave with a metal turn-table. The bowl got arc-welded to the turn table.
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