Can You Put A Thermos In The Microwave?

Whether or not you can put a thermos in a microwave is one of the most controversial issues out there. Can You Put A Thermos In The Microwave?

While it’s generally believed that you can’t or shouldn’t put this metal container inside this opposing metal appliance, many people argue otherwise.

So what is it? Can you put a thermos in the microwave? Simply put, while many people say it can, we say it’s not worth the risk: there are too many variables that can’t be proven or disproved at this point. Instead, opt for alternative products that are microwaveable or can keep your drinks and food hot throughout the day.

Can you really put a thermos in the microwave?

Now, we all probably know why it’s commonly believed that you shouldn’t put a thermos in a microwave.

This storage container is made of metal, usually stainless steel, and metal does not go well with microwaves. 

When this material is placed inside a microwave, it may cause sparks. In turn, these sparks can cause an explosion or fire.

Can You Put A Thermos In The Microwave?

So why are more and more people saying that you can use your thermos inside a microwave?

Let’s first look at the arguments for this question, then some known counter-arguments for why you shouldn’t. But ultimately the choice is up to you.

Reasons why you can microwave a thermos

We are not advocating for this team, but of course we had to familiarize ourselves with their reasoning. So these are the reasons why some people argue that you can use a thermos inside a microwave.

Can You Put A Thermos In The Microwave?

1. Stainless Steel Is Too Thick

Many people argue that the reason metal (such as aluminum foil) creates sparks and causes explosions is because of how thin it is.

So because a thermos has significantly thicker metal walls, they say it won’t get as hot and ultimately never cause sparks.

2. A thermos has no corners

Next, it is believed that sharp corners and edges of metal objects are much more likely to cause sparks. There are plenty of video experiments you can see online that seem to support this claim.

So, because a thermos is completely round and rimless, they think it won’t be as likely to create a spark.

3. The lid is open

Because you open the lid of the thermos when you heat its contents, they argue that there isn’t an excessive amount of pressure buildup that could lead to explosions.

Reasons why you shouldn’t microwave a thermos

Now, as you may have guessed, there are still more reasons why you shouldn’t. And honestly, our position remains that it’s not worth the risk.

Can You Put A Thermos In The Microwave?

Yes, many videos show people heating thick round metal objects with no problem. But we think the risk is still too high, not to mention how energy inefficient it is.

Take a look at some of the biggest reasons why microwaving a thermos is dangerous and, quite frankly, inefficient.


1. How thick are the walls really?

There is honestly no way to know precisely how thick the walls of a thermos really are. So what if, according to Murphy’s Law, you buy a product that actually has pretty thin walls? Is it worth the risk?

Furthermore, most of the experiments are carried out with objects made of pure stainless steel. What if your thermos was made from a more reactive metal?

2. Food or drink will heat up unevenly and slowly

It’s a known fact that everyone said when doing their experiments: because of the thick metal walls, food takes forever to heat up!

Also, the only area where heat can enter the container is at the top, which is usually quite small compared to the volume it contains. So is it worth it?

3. The term “highly unlikely” is used too often

This is something that really annoys us when people try to refute a mostly proven claim. The term used in all of these “yes, you can” articles is “highly unlikely,” so that means there’s still a chance for things to grow.

We know for a fact that metal is reactive in microwaves. Isn’t that reason enough not to take the risk?

When people say “highly unlikely”, they are basically saying “it’s not our fault if something goes wrong, even if we’re trying to convince you otherwise”.

It’s a dangerous term to use and we think it makes their claims less credible. If you’re not willing to back your statement up with safety (and science), you can’t expect others to take that risk.


If you’re siding with the “I’d Rather Not Chance” team with us, then here are some alternative products you can try that will keep your food warm, most of them are even microwave-safe!





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