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Cleaning Thermos Can Be Simple

October 2nd, 2023

Thermoses are one of the most versatile accessories. A thermos keeps our favorite beverage at the optimal temperature throughout the day. Due to its specific shape and design, cleaning may be challenging unless users grasp through the following tips to keep the thermos perfect and avoid deterioration.

Soap and water

Having used the thermos bottle for the whole day to store hot (or cold) drinks, or other types of liquid, we may notice some residues trapped inside. We can clean them with soap and water.

Firstly, pour water in the thermos, close the lid and shake vigorously. Pour out the water and add dish washing liquid, cap the thermos, and shake it well. Remove the cap and drain the flask.


Using water to clean the vacuum flask

Secondly, for the stains which have accumulated for a long time and thus difficult to be removed, allow the soapy water to stay for a few minutes. This will give more time for the soap to act.

Scrubbing tool

Scrubbing tool can be useful to help remove stains.

To remove dirt from the inside of the flask, we may need a scrubbing tool. As some thermoses may have narrow or small top opening, scrubbing tools or toothbrushes may work the best. If a scrubbing tool is missing, we can wrap or tie a washcloth into a stick or spoon and poke it inside the thermos bottle: 

  • Scrub the inside with the cloth wrapped spoon; 
  • Add boiling water to the thermos, cap and shake it well to clean;
  • Remove the cap and drain the water.

Vinegar and Baking Soda

Vinegar and baking soda are effective in thermos cleaning.

Please prepare:

  • Vinegar 
  • Baking soda 
  • Hot water

Note: Baking soda and vinegar have a foaming reaction, so we should make the mixture above the sink to avoid spills.

Pour around half a cup of distilled white wine vinegar into the flask and add around a tablespoon of baking soda. Then fill the bottle up with hot water to free the stains and distribute the cleaning mixture throughout the inner wall.

In order to boost the cleaning power of the baking soda/vinegar solution, let it stay in the thermos for a few minutes before giving it a thorough shaking. 

When the foaming of the soda/vinegar solution has subsided, cap the flask firmly. Shake the flask lightly, and then remove the cap to release pressure. Recap the flask and shake it thoroughly for a minute or so to clean and deodorize it. We can use tools to remove the residue thoroughly. Rinse the thermos with hot water two to three more times.

Rice or Eggshells

Put a handful of uncooked rice in a jar with water and detergents like dish soap. Close the lid of the plug and shake it well to clean. Remove the lid and drain the water.

We can do the same thing using eggshells. Boil an egg and clean the eggshell, then peel and crush it. Put all of the eggshells into the thermos and do the same thing as the rice above.

Lemon juice

If there is any concern over using chemicals to clean the thermos, we can use acidic products like lemon juice. Squeeze a few tablespoons of lemon juice into the thermos flask and leave for one to two minutes before scrubbing and rinsing.


Lemon juice can be used to clean the thermos.

Ice and Sea Salt

Fill about a quarter of the thermos flask with crushed ice, add two to three tablespoons of sea salt. Be sure to close the lid tightly and shake vigorously. The mixture will remove the stains inside. When finished, empty the contents and rinse the flask.

Sea salt used along with crushed ice can also help remove stains.

Tips and Advice

  • Do not put thermos in a dishwasher, as the detergent and the washing process will be too abrasive for it.
  • Bleach can also be hazardous to a thermos, so please avoid using it. Never use chlorine bleach to clean a stainless steel thermos, as the bleach can damage the steel weld.

Cleaning and maintaining the flask in the right way helps increase its durability and also ensure that the bottle is germ-free.

Rang Dong, Vietnam’s leading manufacturer of vacuum flask products, has a range of thermos bottles and flasks that ease customer’s way of storing favorite beverages in a hygienic way. 

Should you have any questions, wish to share your ideas about vacuum flasks or request a quotation, please send us an email to: export@rangdong.com.vn.

Our website: vacuumflask.rangdong.com.vn

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