Can You Put A Thermos In The Microwave? (Find Out Now!)

Emily Carr
by Emily Carr

It’s a cold winter day, and you want to warm up. You have a thermos of hot coffee that needs to be heated, but you’re unsure if the microwave is going to do the trick. Will putting it inside cause any problems?

It’s advised to avoid putting most thermoses in the microwave unless labeled as “Microwave-Safe.” To reheat your thermos-stored food, place the cup in hot water or pour boiling water inside after removing the components. Avoid putting your thermos container in the freezer, as it may result in toxin leaching and food contamination.

Continue reading to find out if it’s safe to put a thermos in the microwave and how to do so. Furthermore, we’ll cover how long thermoses last and if microwaving them impacts their lifespan.

Is It Safe to Put a Thermos in the Microwave?

Thermos LLC is a manufacturer of an insulated, vacuum-sealed, and double-walled flask that preserves the temperature of its components for up to 5 hours. The company was originally created in 1904 but has since become more generalized.

Today’ thermos’ is more of a common term that applies to any type of double insulated flask made of many materials. Typically, it is not recommended to microwave a thermos due to the stainless steel components.

Most thermoses are made of metal or glass. Metal is an electrical conductor and can create sparks and a fire hazard when heated in a microwave.

Glass is generally okay to use inside (unless it came from the refrigerator); however, the double-layered design may not allow for the thermos to expand appropriately. Without this capability, the glass will shatter.

On the contrary, this THERMOS brand container is specifically made to be microwaved. So, it really just depends on the cup. We recommend checking the label and avoiding microwaving your thermos unless it is explicitly labeled as “Microwave-Safe.”

How to Safely Heat Up a Thermos

Since using the microwave is out of the question, what’s the best way to reheat your thermos?

You have 2 options:

  • Pour the components out, and pour boiling water inside.
  • Keep the ingredients inside, and put the entire thermos into a pot of hot water.

While we prefer the first option, let’s talk about how each one works.

Pouring Boiling Water Inside Your Thermos

This choice will require storing your food or liquid in a separate container for the meantime.

  • Put your thermos’ internal components in a different container.
  • Bring water to a boil (enough to fill 3/4 of your thermos)
  • Use caution, and pour the boiling water into your thermos.
  • Put the lid on, and let it sit for 10 minutes.
  • Dump the water into the sink.
  • Refill your thermos with the stored drink or food.

Putting Your Thermos in Hot Water

This seems like the easier solution. Although, it requires ensuring the lid of your thermos is tightly secured and adding a little bit of cooling time at the end.

  • Seal the lid of your thermos, and give it an extra turn to guarantee no water will get inside.
  • Heat up water on the stove- enough to allow your thermos to sit in the pot upright.
  • Bring the water to a simmer and pull the water off the stove.
  • Place your thermos inside for 30 minutes (it takes a while for external heat to penetrate).
  • After the allotted time is up, carefully remove your container and dry it off.
  • Let your cup cool on the outside for 10 minutes before touching.

How Do You Clean the Rust Off of a Thermos?

If your thermos gets a little rusty inside, it’s not too difficult to clean.

To remove the rust from your thermos, follow these steps:

  • Add 1 tablespoon of baking soda to 2 cups of water.
  • Using a toothbrush, carefully scrub the rusty stains on your thermos.
  • Once the spots are gone, rinse and dry your cup.

This process will have your thermos looking as good as new!

How Long Does a Thermos Last?

A thermos is a durable and versatile container.

It’s able to keep foods hot and cold for up to 5 hours and has a lifespan of around 5 years or more. However, this will depend heavily upon the type of thermos you have.

The lifespan of your thermos will depend on how often it’s used and how well it’s taken care of. If you’re looking for a reliable and long-lasting container to store your food or drink in, this cup is the perfect option!

Does Microwaving a Thermos Shorten Its Lifespan?

Because microwaving your thermos is usually not recommended (unless specified), doing so will most definitely shorten its lifespan.

In worst-case scenarios, it can even ruin your microwave. This is because the metal parts of your thermos can create electricity and start a fire.

It’s always best to check the label of your thermos to see if it’s microwave-safe. If it’s not, avoid putting it in the microwave at all costs!

Related Questions

Does a thermos keep ice frozen?

This will vary based on the brand of thermos you bought.Generally speaking, most thermoses are able to keep ice cold for a couple of hours, while other companies claim to retain ice for a couple of days. It’s also going to depend on what’s inside- water and ice, just ice, and how much?No matter what, your thermos should be able to keep your ice-cold for a couple of hours- at the very least!

Can you put a thermos in the freezer?

You can put your thermos in the freezer without damaging the cup. However, freezing temperatures can leach chemicals from the metal into your food or drink.That’s why it’s advised to keep your thermos out of the freezer. If you want to store something cold, you can put it in the refrigerator instead or add some ice cubes to your drink.Additionally, some users suggest that due to the double-wall vacuum design, the components won’t even be frozen. This barrier is constructed to protect the insides from external temperatures anyway.

Is a thermos dishwasher-safe?

Most thermoses can be used in the top rack of a dishwasher. Even though it’s possible to do, it’s still not advised for preserving the longevity of the cup.The best way to clean your thermos is by hand using soap, water, and a gentle sponge.If it’s extra dirty, you can throw it in the dishwasher every once and a while.

In Conclusion

In short, you cannot put a thermos in the microwave without fear of damaging your appliance. The same goes for putting it into the freezer- unless you want to risk leaching chemicals from the metal into what’s inside.

If you wish to warm the internal components, heat up water on the stove and place your thermos inside for 30 minutes, with 10 minutes of cooling afterward. Alternatively, you can empty the insides and store boiling water in the thermos for 10 minutes. Replace the food or liquid when you’re done!

It’s best to wash your cup by hand in order to preserve the stainless steel. Using these care methods will ensure your double-wall vacuum seal stays intact.

Use the methods detailed above to reheat food inside your thermos and enjoy it up to 5 hours later!

Emily Carr
Emily Carr

Emily is a copywriter with over five years of experience in crafting content for the home renovation and remodeling industry. She loves house projects, whether it be painting a room or tweaking small design elements to transform a space. Her favorite aesthetic is french modern because of its clean lines and airy feeling! When not writing, Emily loves to travel and check out architectural details all over the world.

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