There is no stressing enough how handy thermos flasks come in especially in this cold season when a cup of tea does more than quenching your thirst.

However, the problem comes in when you have to properly clean it. Prone to get stains due to it constantly being filled with tea and other hot drinks, getting to the bottom of the surface is a mean task because of its build.

If we’re honest enough, most people clean where they can reach and see. That is, the top and outside surface leaving all the dirt to linger inside. Despite a thorough rinse on the inside, deposits will start to gather in time no matter how much water and soap you use.

Before you know it, your flask has a musky smell every time you open.

A good basic clean with a brush and soap and water does the trick most of the time but every once in a while, you need to get in there and do a really deep clean. This is how.


A tea bag

As ridiculous as it sounds using a tea bag works. Most stains are caused by tea stains and sugar fragments. Put a tea bag into the flask and fill it with boiling water. Close the flask with the lid tightly placed and leave it until the next day. Empty the flask and wipe with a steel wire to remove the stain rings completely.


Bicarbonate of soda or baking soda

Put three teaspoons of baking soda into the flask and fill with boiling water. Leave it to soak for 30 minutes then rinse it clean. This will not only clean but remove any odors within the flask.



Before throwing them away, save your egg shells for later. Dry them out in the sun or oven for a few minutes. Crush them up and pour into the flask with boiling water and shake. The shells will help break up any encrusted residue or stains.



Pour a tablespoon of salt into an empty flask and drop in a few ice cubes. Close the flask and shake it gently. Pour out the ice and thoroughly rinse. This will completely clean of the bottom surface from any stains.


Distilled white vinegar

This is among the best and safest way to clean a flask. To start, ensure the flask is completely dry inside. Pour four tablespoons of the distilled vinegar into the flask and shake vigorously for five minutes and leave it for about 10 minutes to soak in any dirt. Pour the vinegar and rinse it with water.


Lemon juice

Put a few tablespoons of lemon juice in the flask and shake vigorously for about 30-60 seconds. Afterwards, make sure to rinse it out well. You do not want to leave any trace of lemon juice because it can ruin the taste of your tea. To dry the flask, simply leave it open and turn it upside down. 


Dishwasher powder

To clean the inside of a thermos from coffee stains or other stains, put one tablespoon of powdered soap for automatic dishwasher into thermos. Fill with hot water and let it stay overnight with cap off.