Microwaved Currency

Image from Reddit

Contrary to popular belief, you can put metal in your microwave oven. It will not make your oven explode or catch fire. But that does not mean it is a safe thing to do.

Microwaves work by shooting electrons at whatever it finds. The electrons create friction as it passes through the surfaces and generates heat. These electrons cannot pass through a metal surface. When you try to microwave metal, you will see sparks as the electrons skip over the metal surface.

Some chefs have discovered ways of using aluminum foil to direct the electrons to use the skipping electrons to add extra heat to one area of the food. As part of the process, the electrons speed up before finding someplace to go. Another technique is to cover areas to minimize the reaction.

Regardless of how you try to control the flow of electrons, they have to find someplace to go. The reaction is the basis of chemistry. A free electron looks to bond with an atom that has more protons than electrons. It balances the equation.

This basic science lesson is to help explain why you do not want to microwave your currency.

You might have heard that using your microwave oven would help kill the COVID-19 virus. Some research says it is plausible, but the idea is for food. If you have any questions about whether your takeout order is safe, put it in your microwave. You can also heat your food in an oven or on your stovetop. As long as you cook the food to over 140°F (60°C), you will kill most pathogens.

But what happens when you put money in your microwave? It will burn!

The Bureau of Engraving and Printing has produced currency notes with a security thread to thwart counterfeiting since 2003. The security thread is a thin ribbon of metal embedded into the currency paper. Hold the currency up to the light, and it will tell you what the denomination should be. On the $100 note, it is a wider strip with a distinct look.

When you microwave money, the electrons will strike the metal thread, pick up speed, and look for a place to land. The next softest material is the currency paper around the security thread. The increase in friction on the currency paper will cause the paper to burn.

Think of it like this: rub your hands together for a few seconds. You will feel your skin begin to heat. Now multiply your hand rubbing by the speed of an electron flying by, and the friction will burn your hands. That is what is happening to the paper.

If you do burn currency paper, bring all the pieces to your bank. The bank will exchange the notes for ones that are not burned and will send them back to the Federal Reserve for disposal.


First, if you are working with collectibles, DO NOT CLEAN YOUR COLLECTIBLE COINS AND CURRENCY! Cleaning collectible coins, currency, tokens, and medals will reduce their collector value. Just don’t do it!

There are many ways you can clean your circulating pocket change. You can wipe them with a disinfectant, including 70% rubbing alcohol or a household wipe that contains alcohol and Dimethylbenzyl Ammonium Chloride (Clorox and Lyson bleach-free wipes contain this chemical). Another method is to wash coins using warm water and a dish cleaning detergent. Finally, leave coins in your pocket when you wash your pants. The only problem with washing coins with clothes is the racket your dryer will make, and you may dent the drum. Currency may require a warm iron to make flat again.

Another method is using ultra-violet (UV) light.

Image courtesy of Phonesoap, a smartphone cleaning device that uses UV-C light.

UV light is classified into three categories depending on the wavelength. UV-A is the longest wave length. UV-B is considered a medium wave length. UV-C is the shortest wavelength. It is also the most deadly.

The short wavelength of UV-C light will penetrate cell walls and kill the DNA within the cells. We are protected from the Sun’s UV-C light by the Ozone Layer of the Earth’s atmosphere. By destroying the Ozone Layer, we let the Sun’s UV-C light penetrate the atmosphere increasing skin cancers.

While UV-C is altering your DNA to create cancers, it is also killing germs using the same properties to alter its DNA.

You can buy lightbulbs that generate UV-C light. However, if you create a UV-C disinfecting station, be careful. Shining UV-C light randomly will cause skin damage worse than a tanning bed. A tanning bed mixes the spectrum of UV light and filter most UV-C light. But a dedicated UV-C light is not good for your body.

Since UV-C light does not generate a lot of heat, you can create an enclosed disinfecting station using almost any material. One example is to create a box using poster board with the edges sealed with duct tape. Cut a hole in the top for the light and then seal the hole with the duct tape. Place your currency inside the box and leave it for 15 minutes.

If you spend a little more money, you could purchase a wall timer. Set the time for the light to turn on after you leave the room and to turn off 15 minutes later. Do not go into the room until the process completes.

There are commercially made devices made with sealed chambers and timers.

Finally, if you want the safest way to disinfect your money, place it in a plastic bag that seals. Close the bag most of the way. Leave about an inch unsealed. Then let the bag sit in a sunny area for about 24 hours. The natural UV-C light will disinfect the money. When you are ready, remove the money and throw the bag away. Use a clean bag for the next round.

Of course, you can avoid all of this by using a credit card that you can clean with a disinfecting wipe when you get home. Contactless payments, like Apple Pay, Google Pay, and Samsung Pay are also alternatives to paying with cash.

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