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Cleaning and Maintaining Thermos

Tips and Tricks for Cleaning and Maintaining Thermos

Remember your mom saying I kept hot water in a thermos when you caught the common cold. So, have you ever wondered how the water remains hot in the Thermos and also what your mom does for cleaning and maintaining thermos.

I was eager to know how Thermos could keep water hot even after long hours. Also, a question would pop into my mind frequently about what Thermos is made up of and how to clean the Thermos.

In this blog, we will discuss cleaning and maintaining Thermos and briefly discuss the history and working of a Thermos.

The Journey of Thermos

It was 1892 when Scottish chemist Sir James Dewar invented the Vacuum Flask, and the journey of Thermos began. However, Thermos was commercially manufactured only in 1904.

Today, there are multiple thermos brands all around the world. However, the working principle of the Thermos is still the same, which we will discuss later in this blog. 

The Principle Behind Working of Thermos 

The secret behind the working of a thermos is a vacuum. Confused about what a vacuum is? Vacuum here means the absence of air.

 A thermos is usually made up of a double-walled container inside it that acts as an insulator made up of stainless steel, glass, or plastic. The air between the walls is sucked during the making of the Thermos, creating a vacuum. 

When there is no air between the layers, there’s no chance there is heat transfer between the inside and outside of the Thermos.

The absence of air makes it impossible to transfer heat, making heat retained in the place where it is, in simple words, the drinks you keep in the Thermos.

So, the science behind thermos can keep hot things hot and cold things cold simply by making it impossible for heat to escape through heat transfer to the outer environment.

Cleaning and Maintaining Thermos 

clean and maintained thermos and a cup

Cleaning and maintaining Thermos can become easier if you use suitable materials and procedures.

Here are some easy steps you can follow to clean your Thermos in a super easy way: 

For Routine Cleaning 

Routine cleaning of a thermos is essential if you use it regularly. This ensures that your Thermos remains clean without any residue inside it.

What do you need for a routine thermos cleaning? 

  • Mild dish detergent
  • Warm Water
  • Bottlebrush
  • Small towel

Follow these steps for routine cleaning of your Thermos:

  • Add some warm water into the thermo flask along with a tablespoon of mild dish detergent.
  • Let the thermos flask soak the solution for three to five minutes to remove general residues.
  • Using a bottle brush, gently scrub the inner side of the thermos flask, making sure that you scrub all the places inside the Thermos.
  • Remove the water that consists of dish detergent and rinse it with warm water.
  • Try wiping the inside of the Thermos with a small towel and let it dry.

Cleaning to remove stains

If you are thinking of cleaning stains on your Thermos, then mild dish detergent and water won’t be enough to remove the stains.

Following are the things that can help you remove stains from Thermos

  • Baking Soda
  • Vinegar
  • Warm Water
  • Bottlebrush 
  • Small Towel 

Here are a few simple steps to make your thermos stain-free: 

  • Take about half a cup of vinegar and pour it into the bottom of the Thermos.
  • Then, add two tablespoons of baking soda to the Thermos.
  • Now fill up the remaining portion of the Thermos with warm water 
  • Leave it for an hour, then scrub it with a bottle brush.
  • Remove the water and rinse it with clean, warm water.
  • Use a small towel to wipe out water as much as possible 
  • Finally, allow it to air dry.

Cleaning for Removing Grimes 

Though you can use baking and vinegar to remove grime and stains, I have another easy option for removing grime.

Here are materials necessary for removing grime that can be readily available at your home: 

  • Ice and Salt
  • Warm water 
  • Small towel 

Follow these easy steps to remove grime from your Thermos quickly:

  • Add some ice cubes along with a few tablespoons of salt.
  • Close the lid of the Thermos and shake it for a few minutes.
  • You can repeat the process if you’re unsure about grime removal.
  • After completing, rinse it with some warm water.

Removing odors from the Thermos 

I’m sure you also want to remove odors from your Thermos. After you routine clean your Thermos or clean to eliminate stains or grime, you can follow the following steps to remove odors from the Thermos.

  • Add two small cups of white vinegar into the Thermos, cap it, and shake it for around a minute.
  • Now, remove the cap, fill about half of the Thermos with lukewarm water, and use the bottle brush to scrub the inner side of the Thermos gently.
  • Cap the bottle again and shake the Thermos.
  • Finally, Empty the Thermos, rinse it with warm water and allow it to air dry.

What should you avoid while cleaning a thermos for a longer thermos life? 

  • Avoid the use of chlorine or bleach, as they can be too harsh and may damage the stainless-steel interior.
  • Handwashing a thermos is better than using a dishwasher for cleaning a thermos.
  • Follow a regular cleaning routine after using a thermos to maintain a longer life.

Also, if you have a metal water bottle and are confused about cleaning it, get to know the easy steps for cleaning and maintaining your metal water bottle by going through How to Clean a Metal water bottle like a Pro.


Cleaning and maintaining a thermos is easy if you follow the proper steps using suitable materials. As Thermos are helpful for everyday life, it’s important that we clean them regularly as well as keep them maintained for more prolonged use. 

However, the life of Thermos will also depend upon the quality of the Thermos. Better Vacuum Flask is one of the best options if you’re looking for a quality thermos.

Also, Better Home Appliances has a wide range of home appliances, from water bottles to geysers, that are of high quality and within your budget.

So, when are you thinking of cleaning your Thermos?

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