Microwaves were the hottest new thing when I was growing up. Touted as the future of quick and easy cooking, there was one in almost every household. The one thing that I remember being drilled into me by my mother was never, ever put metal in the microwave!
So, is this rule founded on reality or is it more of an old wives’ tale? And what actually does happen when you put metal in a microwave?
Here, we unveil the truth about this golden rule, and fill you in on the how’s, whys, dos and don’ts of using metal in a microwave.
What Happens When You Put Metal In A Microwave?
Contrary to what you may have envisioned, if you put metal in a microwave, you are not going to see a massive explosion or fill your house with “radioactive waves.”
The most dramatic result will likely be arcing or sparking, which can certainly damage your microwave – or maybe you’ll get a small fire. But just as likely, nothing at all will happen. It depends on what metal you’re using.
You may have wondered why some microwaves come complete with a metal rack – seems rather contradictory! Or perhaps when prepping yourself a Hot Pocket you’ve mused about the aluminum contained in the liner.
Why is this safe? The metal in aluminum foil is thin enough that it will not so much reflect the microwaves, but absorb them – and the recommended cooking times are just enough to let the foil get hot enough to crisp your food without catching on fire. However, that doesn’t mean that you can tear off a sheet and use it in your microwave.
As for the metal rack, it’s thick and there are no pointy bits, so it is harmless when used properly.
What if you accidentally put metal in a microwave? If you inadvertently leave a metal spoon, it’s no big deal. It’s things like forks – with pointed tines – that tend to cause arcs and sparks.
Why Can’t You Put Metal In A Microwave?
So now that we know it’s not such a clear cut and blanket rule, let’s find out the answer to the burning question: why does metal spark in a microwave?
Your microwave itself is made of metal, including the walls and the mesh on the window. It’s designed this way to keep the microwaves trapped inside – so only your food is cooked and not the immediate environment – or you!
Without getting too technical, the microwaves in your oven, produced by the oven’s “magnetron,” shoot and bounce around the interior before being absorbed into molecules within foods, liquids, and certain other compatible items, thus heating them up.
The molecules that make up metal items are packed very closely together. They can’t absorb microwaves – instead, reflect them.
Again, it gets a little scientific, but in a nutshell, the reaction between reflected microwaves and the charged air inside the oven causes arcing or sparking.
This can result in either a burned spot on the inside of the oven, perhaps a hole in the oven wall, or even irreparable damage to the oven’s electric systems.
Can You Use Aluminum Foil In A Microwave?
Remember that any foil used in a frozen meal or Hot Pocket is especially designed to be extra thin, so is safer.
Aluminum foil is possibly safe to use in small amounts in your microwave, for short times, but we don’t recommend it. Double check your model’s instruction manual, just to be sure, and always monitor your cooking for the entire time.
SEE ALSO: What Not To Put In A Microwave
Because metal effectively blocks heat, you can use small pieces of foil to protect parts of your dish you don’t want overcooked – like the corners of brownies or the edges of a lasagna.
If you are using aluminum foil, make sure that the sheet never completely obscures your food. There’ll be nothing to absorb the microwaves – your food won’t get hot but the foil will and you are likely to wind up with a fire.
Make sure your foil is smooth, with no crinkled areas – again, you might see a fire occurring.
Can You Microwave Stainless Steel?
Stainless steel isn’t different to any other metal with this method of cooking – it’s still going to reflect microwaves.
Much like other metals, it follows the same general rules outlined above: if it’s a flat stainless steel cookie sheet, not much should happen. If it’s a stainless steel fork, you’re going to see lightning!
In general, although certain metals should be safe in your microwave, we think it’s better to be safe than sorry. That means, avoid putting metal in the microwave.
Electronics can be temperamental at times, and it’s not worth the risk of shorting out your entire oven on the off-chance the metal you use will be safe.