Basically, thermos flasks, also called insulated flasks , function according to the same principle: They consist of an outer and an inner vessel, which are separated from each other by a vacuum layer .
Due to the vacuum, the heat cannot be transported well to the outer wall. In addition, the cold from the outside does not come into contact with the inner wall. This means that the drink inside the jug stays warm for longer. For cold drinks, the principle works the other way round.
1. Closure | 2. Outer shell (plastic) | 3. Inner container (glass) | 4. Vacuum | 5. Mirror layer to reflect heat radiation
In thermos flasks with glass inserts, the inner bottle is mirrored. The reflection reflects the heat radiation back into the interior. Thus, the temperature of the drinks remains constant and the ambient temperature is kept outside.
Common insulated jugs keep warm for up to 12 hours and cold for up to 24 hours .
The material is the most important factor here. High-quality thermos jugs with a mirrored glass bulb keep warm the longest . Jugs with a stainless steel insert usually don't keep the temperature quite as long. Learn more about the advantages and disadvantages of the material here .
Other factors also affect how long it lasts. Insulated jugs should be filled completely. The more air there is inside, the faster the liquid will lose its temperature . Therefore, choose the right size when buying.
" Preheat the vacuum jug with hot water before you pour in the actual drink. This will keep the coffee and tea warm for a long time. For the cooling effect, use cold water." - Kerstin, interior design expert
Thermos flasks made of plastic (1) are lighter, partly cheaper and have an individual design due to bright colours. Thermos flask with stainless steel shell (2) more stable and robust and have a noble look.
Glass insulates better than stainless steel , as it does not transmit heat or cold well and also reflects the heat or cold radiation due to the reflective coating on the inner wall.
Modern thermos jugs often have an insert made of shatterproof stainless steel . Metal does not retain heat as well as glass, here stability is the great advantage . Therefore, stainless steel is often used for insulated bottles and thermo mugs, which should be insensitive during transport.
Keep in mind, a glass inner vessel can break if dropped. There are thermos flasks where the inner glass insert can then be replaced .
Insulated bottles (1): Due to their elongated shape, bottles are especially suitable for carrying in a bag or backpack . Insulated bottles for on the go are usually made of robust stainless steel and have a lid that can also be used as a drinking cup.
On the way to school, to the office or during sports, more and more thermo mugs are being used. Because the small cups are sustainably reusable, robust and practical to store.
Pump jugs (2): Pump jugs are designed for serving and have a large capacity . By simply pressing, many cups can be poured in succession.
Vacuum jugs (3): The design vacuum jug is well suited for use at home , on the coffee table or at the workplace, as it has a capacity that is sufficient for several people or for a longer period of time.
"Many modern vacuum jugs today can rival classic tea and coffee pots in terms of design, making them a harmonious addition to a stylish coffee table." - Kerstin, interior design expert
The tilt closure of Stelton's EM 77 vacuum jug (1) opens by itself when pouring and can be used with one hand. The closure of the design classic can be exchanged with a twist closure at will, so that the jug can be transported leak-proof.
With the classic screw cap (2), the lid is opened slightly for pouring. Most twist-off lids are also completely removable, making them easier to clean. Two hands are almost always needed to open a screw cap.
Thermos jugs should be easy to use. With pressure locks the jug can be opened practically with one hand. With the Quick-Press (3) the lid is opened by pressing a button once before and once after pouring.
A click closure (4), like the push closure, is easy to open with a click. A classic thermos bottle also has a lid that can be unscrewed and used as a cup.
Thermos flasks fizz, when the air in the flask heats up and expands . Due to the design of the thermos, the seal in the lid may not be completely tight. Then the air flows out and the hissing sound is produced .
The phenomenon can be solved in the short term by closing the lid completely or turning it slightly open so that the air can escape more easily.
In general, thermos flasks are available with a capacity of 0.5 litres and thermos flasks with a capacity of 1 to 2 litres . Pump jugs are often even larger with up to 5 litres.
Think about how many cups you want to get out of a thermos. The capacity of the cups you want to use is also interesting. The more you drink, the larger the jug should be and be able to fill a corresponding number of cups.
Drinks cool down faster in a thermos when there is air in the pot instead of hot coffee or tea. So if you only fill the jug halfway because you don't need that much content, the drink in the thermos won't keep warm for as long. Therefore, already choose a vacuum jug in the right size for you when buying.
Thermos jugs are usually not dishwasher safe . Therefore, you should not put your thermos in the dishwasher or submerge it in water when rinsing. If water gets into the vacuum between the inner and outer shell, there is a risk that the thermos will be damaged.
Nevertheless, cleaning a thermos is usually straightforward.
The vacuum jug should be rinsed with warm water after use and set out to dry.
For a more thorough cleaning, some table salt or baking soda can be dissolved in hot water and left to soak in the pot for several hours. For stubborn dirt and to combat coffee smell and taste, a little bit of denture cleaner with hot water can help.
When cleaning, only a soft dishwashing brush and some washing-up liquid should be used. After cleaning, the jug should be rinsed well and stored with the lid open to avoid bad odours inside.
The exterior can be wiped with a damp, soft cloth and then dried with a tea towel.
You would like to buy thermos flasks online but need assistance? Feel free to contact our customer service at any time. We are available to help you with your purchase, give recommendations and can quickly clarify questions. Then let us conveniently deliver your desired item directly to your home.