How To Properly Clean a Stanley Thermos

I love using my large Stanley Thermos to keep coffee or soup hot for hours or even just to use as a water bottle when I'm bushwalking or going to the beach with the kids.

However, my Stanley thermos is super tall and the opening isn't that big so it can be really difficult to clean inside it. Especially when there is leftover coffee or soup caked onto the bottom of it.

Over the years I found a few good techniques and ways to clean my Stanley thermos that get rid of the grime and mold and stop my thermos smelling. So how do you properly clean a Stanley thermos?

For everyday cleaning fill your Stanley thermos with hot water and dish soap and leave to soak for 5 minutes. Brush the inside will a bottle brush and leave to air dry. To deep clean a Stanley thermos putting some steel wool inside and cleaning with a stick works great. Dry rice or a bottle cleaning tablet is another great alternative.

There are a bunch of different ways to clean your Stanley Thermos and I use a combination of these to keep my Thermos is tip top condition, even after I've left it for a week with old soup in it.

First, Rinse Your Thermos Well

It is a good idea to rinse the inside and outside of your thermos before doing a proper cleaning. This is just to get rid of any lingering food or drink particles.

I like to fill my thermos with warm water and give it a good shake for a quick rinse.

If you have the time then soaking your thermos with hot water will help soften up everything inside making it easier to remove.

When I've left my thermos with old soup of coffee that has caked to the sides I fill my thermos up with either hot water from the tap or I actually go to the effort of boiling the kettle and using boiling water.

I then leave the water to sit for anywhere from 5-30 minutes, or even longer, depending on how caked on the food is. This makes cleaning the inside of the thermos with your bottle brush so much easier.

Get A Firm Bristle Bottle Brush

Because my Stanley Thermos is super tall it can be really difficult to clean the inside sometimes.

I've tried a bunch of different bottle brushes over the years and I find brushes with soft bristles make it harder to clean the inside compared to bottle brushes with super hard thistles.

You always want to get a rounded bottle brush like this one at Amazon so that you can easily scrub the bottom of the thermos and not just the sides.

The Trazon Dish Brush Set comes with 3 different bottle brushes. But what I like about this set is how firm the bristles are. Perfect for cleaning a Stanley thermos.

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If you don’t own a bottle brush there are some other alternatives like a cloth or a sponge on a stick.

Although, be warned, cleaning with a sponge and stick is harder than it looks!

However, sometimes I will do this with steel wool to REALLY clean the inside of my thermos when it's stained and needs a solid clean.

Everyday Cleaning: Use Dish Soap and Water 

You should ideally be washing your Stanley thermos after each use, and you can do this by using warm water and your usual dish soap. Any brand will work. 

How to wash your thermos using dish soap and water:

  • Fill the thermos with warm water and a small amount of dish soap
  • Leave inside the thermos to soak for 5 minutes 
  • Close the lid and shake for thermos for 30 seconds 
  • If you own a bottle brush you can scrub the inside of the thermos 
  • Open the lid and empty the soapy water 
  • Using the emptied water wash the outside of the thermos
  • Rinse thoroughly and dry 

Once dry, you can use your thermos immediately after. 

IMPORTANT NOTE: Store Your Thermos With It's Lid Off

One of the big mistakes I made was after cleaning my thermos I would store it with the lid on. It make sense to keep everything together.

However, I found that unless I cleaned and dried my thermos perfectly that when I would open the thermos it would smell a bit funky, especially if it's been months since I used it.

By storing your thermos with the lid off you ensure it stays dry and it won't harbor and grow mold from the tiny bits of moisture trapped inside it.

ALSO IMPORTANT: Don't Forget To Clean The Rubber Gasket

When you're cleaning your Stanley Thermos make sure that every so often you take the rubber gasket from the lid off and give it a good clean as it can accumulate mold over time.

To remove the rubber gasket use your fingers to pull it off or use a dull butter knife to remove it being careful not to cut or break it.

Give the rubber gasket a good scrub with a brush or dish cloth and make sure you also clean in the lid where the rubber gasket sits.

Once clean rinse and dry before putting the rubber gasket back on.

For A Deep Clean: Use Dry Rice

Even if you have a thick bristle bottle brush sometimes there can be hard to reach places (like the top of the neck of the bottle or the base) that are difficult to clean.

If you're noticing staining, residue or a funky smell in your bottle then one of the best ways to give the inside an incredible good clean is using dry rice.

This works because dry rice acts as an abrasive. When you shake your bottle with rice in it the rice granules hit the sides and brush away any residue.

What you'll need:

  • 1 cup of dry rice (white or brown is fine)
  • Small amount of dish soap
  • Hot water

How to clean your thermos using rice:

  • First I like to soak my thermos in hot water for 5-10 minutes to soften any residue
  • Empty the thermos and pour in approximately 1 cup of dry rice
  • Squirt in some dish soap
  • Fill 2/3 full with hot water
  • Close the lid and shake the thermos vigorously for 1-2 minutes
  • Drain out the water
  • Remove the rice and discard
  • Rinse well and dry

You can see how well this technique works in the video below:

Cleaning Using Denture Tablets or Bottle Cleaning Tablets

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This may sound odd, but denture tablets and bottle cleaning tablets are a great way of cleaning your thermos and removing build-up inside the thermos. 

What you need: 

How to clean your thermos using denture/bottle cleaning tablets: 

  • Fill the thermos 2/3 with warm or hot water
  • Swirl the water around the inside. You want the entire thermos to be wet inside 
  • Place 1 – 2 denture/bottle cleaning tablets inside the thermos 
  • There may be a chemical reaction, so leave the thermos in the sink and do not put the lid on
  • Leave to soak for 30 minutes 
  • Using a bottle brush or sponge, scrub the inside of the thermos 
  • Empty the water and rinse the thermos thoroughly to remove any leftover denture tablet residue

These tablets often use a combination of citric acid plus other chemicals to cause a reaction that removes residue from the walls of your bottle and kills bacteria leaving it super clean.

This is a really easy and lazy way to clean your thermos but also leaves it smelling great.

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Cleaning Using Baking Soda and Vinegar 

Instead of buying cleaning tablets you can get a similar result with baking soda and vinegar.

Vinegar is great as it's a natural mold killer and baking soda is a natural cleaning agent and abrasive. Combined they cause a reaction which makes for even more effective cleaning.

You will notice that this cleaning mixture comes up all the time when researching ways to clean a thermos, and this is because it is such a great method.

Stanley even lists it on their website as a recommended cleaning method. 

White distilled vinegar is great at removing foul smells from a thermos, which is what a dirty thermos is often plagued with.

What you will need: 

  • Baking soda 
  • White distilled vinegar 
  • Hot water 
  • Bottlebrush

How to clean a thermos using baking soda and vinegar:

  • Pour in the white vinegar. 
  • Add one tablespoon of baking soda to the thermos. You will notice that the mixture will start fizzing and frothing 
  • Once the chemical reaction has subsided, you can pour in the hot water 
  • Leave the mixture to stand for 10 minutes. This will remove any tea or coffee stains inside the thermos.
  • Scrub inside the thermos well using a bottle brush
  • After 10 minutes, empty out the thermos and rinse the inside thoroughly. I suggest rinsing the thermos twice. 

As tempting as it, do not place the lid on the thermos when filled with vinegar and baking soda. This is because the mixture is very reactive and releases gas and this can make the lid difficult to get off.

Only white distilled vinegar should be used as brown vinegar smells and will make your thermos smell vinegary. 

Cleaning Using Salt and Ice

Not only is salt awesome in food, but it can be used to clean your thermos because it has natural anti-bacterial properties. 

The reason salt works is that when you shake the bottle the salt particles smash up against the sides and it scrubs the inside of it…that is until the salt is dissolved. This is similar to the rice method but you are using salt and ice as the abrasive instead of rice.

What you will need: 

  • Crushed ice or small ice cubes 
  • Salt (Sea salt or Kosher salt) 

How to clean a thermos using salt and ice: 

  • Fill the thermos with your ice a quarter of the way fill 
  • Add 2-3 tablespoons of salt. For a smaller thermos, use two tablespoons of salt 
  • Close the lid and make sure it is secure 
  • This is the fun part, shake the thermos like you’re making a cocktail. Do this for one minute.  
  • Empty the thermos and make sure to properly rinse the salt from it. Salty coffee is not recommended. 
  • Dry with a paper towel or leave to air dry

Shaking the full thermos allows the rubbing of the ice and salt to exfoliate and clean the inside of your thermos. It is also a great chemical-free alternative. 

You just need to be quick once you’ve added the salt, as the ice will begin to melt quite quickly.  

Dry rice is a great alternative to this, as these rice particles shrub the insides of the thermos.  

Cleaning Using Dishwasher Powder 

This is a great cleaning alternative if you don’t have any liquid detergent, as the powder exfoliates the inside of the thermos. 

What you will need: 

  • Dishwashing powder 
  • Hot water 
  • Bottlebrush or sponge

How to clean the thermos using dishwashing powder:

  • Put one tablespoon of dishwashing powder in the thermos 
  • Pour hot water to the brim 
  • Close the lid and shake the thermos for 10 seconds  
  • Leave the liquid in for as long as you like. Some people leave it in the thermos overnight. 
  • Pour half the liquid out and, using a bottle brush or a sponge, scrub the inside of the thermos
  • Rinse and dry the thermos using a clean towel