Did you know, the vacuum flask was invented in 1892? Dewar flask, named after its inventor, Sir James Dewar was initially used for storing chemicals at a stable temperature! Today, a flask or an insulated water bottle is a popular household item! Over the years, just like every other thing, the flasks have evolved too. You can find high-end insulated water bottles in various different sizes, shapes and colors! Not just sustainable, the insulated water bottles are smartly engineered to retain the temperature of your drinks, hot or cold, for longer!

How does an insulated bottle keep your steaming-hot coffee hot and chilled lemonade cold?

An insulated water bottle is quite different from your normal stainless-steel bottles. Insulated bottles have double layers with vacuum between the two layers. This vacuum effect is created because when there is no air, there is no transfer of heat! So, a vacuum insulated flask keeps your coffee hot by retaining the heat, while it keeps your chilled lemonade cold by shielding it away from external heat!

This simply means you can enjoy a cup of hot coffee from your flask even hours after brewing it, all you need to do is pour it hot into a flask! To quench your thirst in summer, fill your flask with ice-cold water, and you can have chilled water from the flask for up to a few hours straight!

Now that it’s established how capable an insulated water bottle could be in retaining the temperature of your beverages, the focus shifts to cleaning the bottle after every single use! Your insulated bottle can be handy; however, it needs to be thoroughly cleaned after every use when you carry your favorite beverages.

1.Tea – The magic of a hot cup of chai cannot be replaced by anything else! Mid-morning in your office or an early evening on your porch, sips of hot chai from your insulated bottle along with something to munch on is all you need to get you excited! Tea definitely has an aroma that lasts longer even after you rinse your flask with water. Your flask will need to be cleaned with a detergent to make this odour disappear.

2.Coffee or Latte –The bitterness of coffee tastes terrific, and it makes for a great pick-me-up drink. Carrying your fresh brew in your thermos flask to work is a great idea, cleaning the flask with a mild detergent after you reach home is an even better one!

A rinse with tap water is a great idea after you finish up, however, a few easy steps to thoroughly clean it after you get back home will make your flask all ready for the next beverage you plan to carry! The list of beverages that you can carry to work, gym, shopping or for that quick meeting with a friend in park is quite endless –

  • Hot chocolate
  • Soup
  • Hot oatmeal
  • Warm milk
  • Infused water
  • Congee
  • Rasam

Here is also a small list of cold beverages that you can carry in the thermos flask –

  • Iced tea
  • Cold coffee
  • Chilled Milk
  • Smoothie
  • Fruit juices
  • Dalgona Coffee

Getting the odour and stains out of your flask

Investing in an insulated bottle with a wider mouth makes cleaning a breeze. However, the construction and design of insulated bottles often demand a proper cleaning process and maintenance, more so if you are using the bottle for storing your coffee and juice! A deep cleaning procedure once in a while along with conventional detergent-and-water method you normally follow works wonders in keeping your flask squeaky clean!

1.Detergent and a soft brush

For mild stains and a persistent odour in your thermos bottle, using detergent can be an easy cleaning solution. Detergent not just removes the odor, but also weakens the tough stains that have settled, making it easy to scrub them out. Add warm water to the bottle. Add a scoop of mild detergent and allow it to settle for about 2-5 minutes, by which the accumulated dust will weaken.

Use a brush with soft bristles to scrub off the scrap, if any, left in the flask. Gentle scrubbing allows to get rid of the micro particles that are settled at the bottom of the bottle. Rinse again with warm water to ensure the detergent is completely washed off. This method is simple, quite effective and quick too.

Make your own cleaning detergent at home

If you are someone who finds it unsafe to use the chemical infused products for cleaning your bottle, this is just for you! A DIY project that helps you come up with a make-at-home detergent for cleaning a vacuum flask is quite easy. Use natural ingredients that are available at home and make your own bottle-cleaning detergent-

  • ½ cup white vinegar
  • 2 tbsp baking soda
  • Ten drops of tea tree oil or any essential oil you have at home

Add the essential oil to the vinegar. To this blend, add baking soda and pour in a bottle. Add water (approximately 2 cups) to this. Then, gently shake to mix all the ingredients and, voila, you have your own handmade cleaning detergent. You can dilute this with more water if you find it strong!

2.Dishwasher Detergent

This is one of the easiest methods to clean a flask. You can use a dishwasher detergent that is readily available in the market. The method is simple and easy to implement; you just have to pour about one tablespoon of dishwasher detergent to warm water, shake it thoroughly, and leave this mixture for several hours. Rinse it with tap water, and leave the bottle open for a few hours to get the detergent smell out of the way!

3.Vinegar with baking soda

If you are regularly carrying caffeinated beverages, your thermos may have some tough stains, which you may find, are not easy to remove. The strong odor and tough stains probably need something strong, just like how you prefer your coffee! Cleaning the flask with bicarbonate soda is a simple method but with useful results. Vinegar mixed with baking soda will create foam as the mixture reacts. Here is a method you can follow with these ingredients-

  • Vinegar
  • Sodium Bicarbonate (Baking soda)
  • Warm Water

Pour a spoon of vinegar with half spoon of baking soda into your insulated bottle. The mixture will froth up. Once the froth settles, add water. Avoid covering the bottle lid due to the reactive nature of the mixture. Leave it for about 10 minutes or more depending on the stains. Later, a brush can be used to wipe out the stains quickly. Rinse the bottle again to make sure that the vinegar and soda mixture is thoroughly removed. Cleaning a flask with bicarbonate soda is one of the most effective and trusted ways for cleaning the deep stains in it.

4.Salt and ice cubes

Exfoliating is great for removing not just dead skin from your face, but super effective for removing the scale from your insulated bottle! Gentle exfoliation with readily available ingredients at home is easy, efficient, and it doesn’t affect the inner surfaces of the bottle.

Fill a quarter or half of the bottle with ice cubes, preferably small cubes or crushed ice. Sprinkle 2-3 spoons of salt over the ice. Larger salt grains like sea salt work well for cleaning. However, if you have normal table salt at home, it does the job too. Just be a little generous with the salt! Shake the bottle for about 2 minutes gently, making sure the ice and salt mix reaches every nook and corner of the bottle. Leave it on for a few minutes, and rinse with tap water. This can be done weekly, or twice in a month as needed!

5.Lemon Juice

Acidic products generally work well for cleaning surfaces! However, it is important to understand the design of your thermos to come up with one magical ingredient that will make cleaning mush simpler! Squeeze a few tablespoons of lemon juice into your flask along with a glass of water. Shake it well for a good minute or two, and later rinse with water. Lemon juice alone is capable of getting rid of the odour and stain accumulated in your insulated flask.


Yet another easiest and effective solutions to get a spotless and clean bottle is by using teabags. To get rid of the stains in your bottle, add boiling water to a teabag kept in the flask. Leave the mixture overnight. In the morning, empty the water and teabag mixture, and rinse well with tap water.

7.Denture tablets

Denture tablets are a gentle and easy answer for cleaning a flask at home. Pour hot water into the bottle along with a denture tablet. Leave the bottle open, without its lid. The mixture will react, foaming and then settling. Let it rest for about 30 minutes and you can rinse well with tap water.

What are denture tablets?

Denture cleansing tablets are gentle and widely used for cleaning insulated flasks. The main ingredient in these tablets is sodium bicarbonate. It has the property to wipe away the stains and dirt. The tablets are widely used for cleaning crusty surfaces of casseroles, coffee tumblers and flasks!


Insulated flask is a great invention, thanks to its capacity to retain the temperature of the beverage poured in for a considerable amount of time. A delicious beverage at the right temperature is all that is needed to turn a dull moment into a brighter one! No one says ‘No’ to a bowl of warm soup on a cold day, and a glass of refreshing sherbet on a warm summer day! An insulated drinkware makes for a great investment, it helps in keeping you hydrated, while you can enjoy your favorite drink just the way you like it,warm or cold!

The design and construction of most flasks are different, and it is important to follow the cleaning instructions that come with it. While picking up a flask, choose one with a wider mouth, it makes cleaning and loading your drink in it both easier! While you are buying a flask, add a cleaning brush with gentle bristles to your shopping cart and half the job of maintaining bottle hygiene is done! A tap water rinse after every use followed by a deep clean method once you reach home is the routine that will help in keeping your bottle spotless, and odour-free too!