Tell Mrs. Adams marshmallows are nothing to worry about, if you use a little finesse. I like to put one jumbo-sized marshmallow on a small plate or in a medium-sized bowl on high power (~1100 watts) for under a minute. You’ve got to keep your eye on it as it balloons, then relaxes, and hit stop before it overruns your dish and/or hits the ceiling of the oven. The flavor will be burned-ish and the texture will be anywhere from perfectly chewy to alien and unpleasant on the teeth. Whatever you do, be sure to brush afterward.
Welcome to the Straight Dope Message Boards, Katishaw, we’re glad you’ve found us. For future ref, when one starts a thread, it’s helpful to other readers to provide a link to the column in question. Saves search time and helps keep us on the same page. No biggie, and johnpost has kindly provided it. You’ll know for next time, and, as I say, welcome!
I remember the early days of microwave ovens. It was the 1970s, and 7-Elevens started having them to heat up food. I was in one in Texas when another customer came in with a bag of food from a hotdog chain called Der Wienerschnitzel. He asked the clerk if he could heat it up in the microwave. The clerk said sure. A few moments later, the guy yelled out, “WHAT’S WRONG WITH YOUR MICROWAVE??!!?” His food was all on fire. Seems Der Wienerschnitzel at that time wrapped their hotdogs with paper that had some foil threads running through it.
Metal works as an imperfect reflector in a microwave. That has 2 effects:
It keeps your food cold and uncooked if it shields the food. This is why you wrap foil around the the ends of chicken legs: to stop the end of the leg from over-cooking.
The metal gets hot, just like water does, from the energy it absorbs instead of reflecting. This causes the metal to melt and/or oxidise (burn).
Metals reflect better if they are better conductors, like aluminium. They burn better if they have a lot of surface area, like steel wool.
There is also another thing happening: you can get sparks (lightning) between two metal points. The spark can heat the metal even if the metal is reflecting well. A thin continuous gold ring on a dish will first get hot due to circulating currents, then fail at some point, then spark and arc at that point.
If you want to put a metal rack into your microwave, you should first make sure it is solid enough so that it can handle the heat, including any heating it gets from the microwaves. Then you should try to choose a metal that is either a very good conductor, so it reflects well, or a very bad conductor, so that it absorbs very little. Thirdly, you should shape it so that it has no adjacent points for sparks: only very large gaps where it has gaps.
In general, it is safe, but pointless, to put an aluminium pan into a microwave: the aluminium pan will protect the food from cooking. You may be able to damage your microwave if you run it without anything to cook.
And in general, it is safe to protect small parts of your food with aluminium foil: it seems to work ok.
Put a wrapped granola or Nutri-Grain bar in the microwave for 10 seconds and enjoy.
A marshmallow in the microwave will just keep expanding. Did this with some friends & the plastic bowl broke before the microwave did (and we irradiated the hell out of that marshmallow).
MODERATOR NOTE: THere were two threads on the same topic, which I’ve now merged. This probably creates a wrinkle in the trouser-leg of time, but them’s the breaks. – CKDH
