Best Thermos Flask

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Thermos flasks are essential for when you are out hiking or completing any outdoor activities for that matter! Whether you are a tea or coffee lover, or even wanting to take hot soup on your walks with you – there will be a thermos flask for you. There are even thermos flasks that are now designed for keeping cold drinks refreshingly cool for those warm summer walks.

As wonderful as thermos flasks are, there are plenty of flasks out there that really aren’t worth your money! They will leak in your bag, leaving your other precious belongings wet and stained, or you may just find your lovely warm brew more resembling an iced tea! There really is nothing more disappointing when you are trying to enjoy a nice walk! Our article aims to provide you with all the information you need to make an informed purchase of a thermos flask!

What to Look For in a Thermos Flask

Thermal flasks will have particular features that make them good at what they do – keeping your drinks warm or cold! Choosing the model with these features will leave you able to reap the benefits of your informed purchase!


The capacity of your thermos flask is one of the main factors that you need to consider. They will range between around 250ml, all the way up to 1L. It is important to remember that bigger isn’t always better! Yes, a larger capacity will mean that you can take more liquids out with you when you are out and about, but this also means more to carry and can lead to more waste if you do not end up using it all.

Consider how long you are usually going to be away from home for (and therefore using your flask) as this will give you an idea of how much you are likely to need. It is also worth considering whether they will be anyone with you that you may have to share your drinks with!

TOP TIP: If it helps, it is worth considering that an “average” size cup of tea is around 200ml (depending on the cup of course). So if you purchase a 600ml capacity thermos flask then that will be enough for 3 cups of tea while you are out and about!


Thermos flasks are made out of different materials but the most common are stainless steel or plastic. Plastic models will be considerably cheaper and lighter than metal models, however they won’t retain the heat nearly as well as stainless steel models and are more prone to breakage if they are dropped or knocked. Metal flasks are also easier to clean, which is vital if you are planning on using your thermos flask for different things – last thing you want is a tea tasting of coffee or a coffee tasting of soup!

Another benefit of stainless steel is that it won’t leave that metallic taste that other metals will when you are drinking. It is important to consider though, that they will be slightly heavier (although more modern models are getting lighter and lighter).

Heat Retention

The heat retention for your thermos flask is crucial – without it you might as well just buy a normal flask! Thermal flasks vary massively in the different levels of heat retention they can offer, as this depends on the way in which they have been made and the different materials that they are made from. Some will only be able to keep your drinks warm for around 3 hours, whereas others will be able to keep them warm all the way up to 20 hours! This makes a massive difference if you are planning on going for a long walk or journey that means you are going to need your drinks or food to last all day!

If you are wanting to use your flask for cold drinks as well then you will need to check that it is up to the task, as some flasks won’t work with cold drinks and you will soon find them back to room temperature! However, if the flask is compatible with cold drinks then you will usually find they can keep drinks cool for longer than they can keep them hot – sometimes up to 24 hours!

Flasks that will be most effective in keeping your drinks warm (or cool) will be double layered or vacuum sealed, so these models are well worth looking out for when making your purchase!

TOP TIP: If you pre-warm your flask using hot water before filling it with the drink or soup that you are wanting to use then it will stay much warmer for longer!


There are many different styles of lids that can be found on thermos flasks and the lid that is right for you largely depends on both personal preference and what you are going to be using your flask for. Regardless of this though, you need your lid to be secure and tight, with a good water-tight seal. This is crucial if you are going to be carrying your thermos flask in a backpack! Equally, you do want the lid to be easy to screw on and off – the best way to check for this is reading different reviews online!

If you are going to be wanting to store a thicker liquid, such as soup, in your thermos then you will need to purchase a flask with a larger lid and pouring option, many of these will come with a “cup” that forms as part of the lid so that the liquid can be served into this and drank in a more conventional manner.

However, this type of lid will be less than ideal for anyone that is wanting to have their drink on the go, as it will easily lead to spillages. If you are going to be drinking your drink whilst out walking or on the go then you will need a smaller opening on your lid that will let out less liquid at once – this is also better for heat retention if you are needing your liquids to stay warm for longer!

Extra Features of Thermos Flasks

If you are looking for the best thermos flask for your money then it is well worth watching out for these extra features when you are trying to find the right one for you…

  • Handles – A handle on your flask can make your life so much easier when you are trying to drink out of it (particularly if the flask is hot or you have bought a particularly large model). However, make sure to remember that this will add to the amount of space that it takes up when you are carrying it around, and may stop it fitting in the handy outer pockets of some backpacks that are designed for flasks!
  • Warranty – Many of the best thermos flasks will come with a warranty/guarantee, which is important to look out for! If you are going to be paying a decent amount of money for your flask you want to know that it is going to last and be up to the task!
  • Silicone cover or fabric casing – Some flasks will come with a silicone outer cover that will help to protect the flask from dents and scratches if you drop it. Others will come in a fabric casing, which not only protects from damage but will also soak up any leaks and save other items that you have near the flask (although these do make the flask more fiddly to use!).
  • Consider a lid with two openings – Some flasks will only have one, small opening, which is fantastic for keeping your drinks nice and warm, but this makes it very difficult and time consuming to fill your flask – we would recommend having two different parts to the lid – a larger part for filling the flask and then another part for drinking or pouring.
  • Vintage flasks – There are many “traditional” vintage flasks that are available for sale that have a much more classic look than modern flasks. If you are looking for a more quirky, stylish purchase then this might be for you, but they are usually smaller and may not retain heat as well!

Frequently Asked Questions

How can I clean my thermos flask?
For general cleaning, you can wash your thermos flask in the same way that you would wash the rest of your dishes – simply use warm water and washing-up liquid. Just remember to rinse it with hot water afterwards! Occasionally though you will need to do a deep clean with your thermos flask. This can be done using hot water and one teaspoon of bicarbonate of soda. Leave this to soak for a while (but do not put the lid on your flask!) and then rinse with hot water.

How long will tea/coffee stay fresh for in a thermos flask?
Hot drinks, such as tea and coffee, will still be able to be drunk after around 8-10 hours in a thermos flask (sometimes longer depending on the quality of the products that you have used). Any longer than this and you will probably find them not taste quite the same!

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