How does a thermos flask work?
A thermos flask for coffee or a travel mug can keep boiling water hot or cold water cold.
The material is typically stainless steel, and the metal sides have an insulating effect that helps the contents stay warmer or cooler than the surrounding temperature.
If you choose a thermos flask, you can use it to take hot water for coffee on trips, or use it as a food flask for things like baby purée. It also works well as a metal drinks bottle to take to work, study or on daily journeys.
On our table setting pages, you can explore more serving and drinkware categories, and under jugs and carafes you can compare thermos flasks with other products for serving and carrying drinks.
Benefits of using thermos flasks
Thermos flasks and other insulated products are practical when you are heading out.
That applies whether you are spending time outdoors or have many hours of travel by car or train ahead of you. A longer journey is easier when you have coffee with you, and tea is just as pleasant when you can drink it at your own pace while you are away from home.
For many shoppers, this category is a practical place to start when the main need is to keep drinks or food at the right temperature on the go. If you are instead looking for serving pieces for the table, you can continue to categories such as serving jugs, water and wine carafes or decanter sets.
How to clean thermos flasks
Has the taste of coffee stayed in one of your flasks, and now you want to use it for tea or baby purée instead? There is a simple way to deal with that.
Try adding 1-2 tablespoons of baking powder to the flask, then fill it with boiling water. Leave it overnight if possible, or for at least 30 minutes.
After rinsing the flask thoroughly with water several times, it should be fresh again, without any remaining coffee taste.
Can thermos flasks go in the dishwasher?
That depends on the brand.
Some metal drinking bottles can be washed in the dishwasher, while others cannot. It is always best to check what your thermos product is designed to handle.
What you can rely on is hand washing with washing-up liquid and water. For thermos flasks in steel and similar insulated cups, that is always a safe option.
A practical thermos flask with cup
It is useful to have an insulated drinks flask available.
That way, you can take coffee with you or keep your drinking water cold, even on a warm summer day. If you choose a thermos flask with an integrated cup in the lid, you get two functions in one: a bottle for storing coffee, water or something else, and a cup to drink from while you are on the move.
When comparing products in this category, a practical way to choose is to start with what you want to bring. Some shoppers need a flask mainly for coffee or tea, while others are looking for a food flask or a bottle for cold water. From there, it becomes easier to narrow down your choice by size and design.
Should you choose a large or small flask?
If you are looking for a thermos flask for children, a small 0.5 litre flask can be a suitable option. It can be used for drinking water, or filled with baby purée or yoghurt.
You can also find children's flasks decorated with child-friendly motifs and playful colours. For some, that makes them more appealing than classic grey or black designs.
If you want a flask to take with you and need enough drinking water for the whole family, a larger thermos flask of 1 litre or more can be a better match.
For most situations, size is one of the easiest ways to compare products on the page. Smaller flasks are useful when you want something compact for one person, while larger models give you more capacity for longer outings or shared use. You can also compare whether you prefer a classic flask shape, a travel mug format or a model with a cup built into the lid.
How thermos flasks fit into the wider range
Thermos flasks are one part of a broader selection of jugs, carafes and insulated serving products. If you are comparing options across the range, it can help to think about whether the product is mainly for taking drinks with you, serving at the table or keeping drinks warm during a meal.
If your focus is table service rather than transport, you may also want to look at vacuum jugs, which are a relevant alternative within the same overall category. For hot drinks served at the table, teapots and milk jugs can also be useful to compare with. And if you are browsing pieces for sauces or smaller table service details, you can continue to gravy boats.
Here on the page, you can explore thermos flasks from brands including Thermos, Alfi, Funktion and Tiger. That makes it easier to compare different looks and formats in one place and choose the thermos product that matches how you want to use it.
Frequently asked questions
How does a thermos flask keep drinks hot or cold?
A thermos flask is typically made from stainless steel, and the insulated metal sides help the contents stay warmer or cooler than the surrounding temperature. In everyday use, this means that hot water, coffee or cold water can hold their temperature for longer while you are out and about.
What can I use a thermos flask for?
A thermos flask can be used for hot drinks such as coffee and tea, but it can also be used for cold water or food such as baby purée. In practice, this helps you use the same type of product for work, study, travel or day trips, depending on what you want to bring with you.
How do I choose between a small and large thermos flask?
The main difference is capacity, so it helps to start with how many people it needs to serve and what you want to carry. In everyday use, a smaller 0.5 litre flask can suit one person or a child, while a 1 litre flask or larger can be more practical for longer outings or family use.
Should I choose a classic flask, a travel mug or a flask with a cup in the lid?
This depends on how you want to use it day to day. In practice, a classic flask may suit carrying more drink, a travel mug can be useful for drinking on the move, and a flask with a cup in the lid makes it easier to pour and drink without needing a separate cup.
How can I remove a lingering coffee taste from a thermos flask?
You can try adding 1 to 2 tablespoons of baking powder to the flask and then filling it with boiling water. Leave it for at least 30 minutes, or overnight if possible, and then rinse thoroughly several times. In practice, this helps freshen the flask so you can use it for tea or baby purée instead.
Can thermos flasks go in the dishwasher?
That depends on the brand, as some insulated bottles are designed for dishwasher use and others are not. In everyday use, this means it is best to check the product guidance first, while hand washing with washing-up liquid and water is the safest general option.
What should I compare when choosing a thermos flask online?
A practical place to start is with what you want to bring, such as coffee, tea, cold water or food. This makes it easier to narrow down the filtered choices by size, shape and design, including whether you want a classic flask, a travel mug format or a model with a cup built into the lid.
What is the difference between a thermos flask and other drink-serving options?
A thermos flask is mainly designed for carrying drinks or food while helping to keep the contents at the right temperature. In practice, this makes it more suitable for travel and daily journeys, while products such as serving jugs, carafes and teapots are more focused on table service.