Fact check: Microwaving a penny won't shrink it, and it might damage your microwave

Chiara Vercellone, USA TODAY
·3 min read

The claim: Microwaving a penny for one minute will shrink the coin

Most everyone knows some things are not meant to be microwaved, like metal for example.

But some social media users are contradicting that, claiming microwaving a coin will shrink it. It's a claim that is both wrong and dangerous.

"Microwave a penny for one minute to get a mini coin," reads the caption of an image posted July 29, which has been shared over 700 times.

It's part of a long-running prank on various social media platforms, where posters try to trick others into attempting the potentially dangerous action.

The image is a screenshot of a tweet, but the username and date have been cut off. The tweet featured an image of the purported shrunken coin next to a regular-sized penny.

According to Snopes, the image originated in November 2019 on Twitter, but the original account has been suspended. A screengrab of the tweet posted on Reddit shows it had been retweeted more than 11,000 times within one week of posting.

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Putting a coin in a microwave won't shrink it, however. And it could cause harm to the microwave, potentially starting a fire.

USA TODAY reached out to the poster for comment.

Microwaving metal could cause dangerous sparks

Videos of coins being microwaved posted online show sparks appearing almost immediately after starting the microwave.

That's because of how microwaves work.

Microwaves have a magnetron inside that converts the electric power it receives from the wall plug into very short radio waves, according to the U.S. Food and Safety Inspection Service.

That power is transmitted through the magnetron at a high frequency, which then allows water, fats and sugars to absorb it and heat up.

When the energy waves come into contact with metallic materials, it creates sparks due to the high temperature, also known as arcing. The Food and Safety Service recommends stopping the microwave immediately if sparks occur because they can damage the oven and the metal object.

The reaction is milder if the metal has a smooth surface, like a spoon, Live Science reported in 2019.

Regardless, the reaction doesn't cause any metallic objects to shrink.

While the origin of the smaller coins posted on social media isn't clear, they could be props used for magic tricks.

Our rating: False

We rate the claim that microwaving a penny for one minute will shrink the coin FALSE, based on our research. If put in the microwave, the coins will start to spark, but they won't shrink.

Our fact-check sources:

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This article originally appeared on USA TODAY: Fact check: False claim a coin will shrink if microwaved