Buying vacuum flasks online: how to find the ideal model
1. How do vacuum flasks work?
How are vacuum flasks made?
Basically, vacuum flasks and vacuum jugs all work on the same principle: they consist of an outer and an inner container separated by a vacuum layer.
The vacuum prevents heat from travelling easily to the outer wall. At the same time, the cold outside doesn't come into contact with the inner wall. This keeps the drink inside warm for longer. For cold drinks, the principle works the other way round.
1. Lid | 2. Outer casing (plastic) | 3. Inner container (glass) | 4. Vacuum | 5. Mirrored layer to reflect heat radiation
Why are vacuum flasks mirrored inside?
In vacuum flasks with a glass liner, the inner flask is mirrored. The mirrored surface reflects heat radiation back inside. This keeps the temperature of the drink constant and keeps the ambient temperature out.
How long do vacuum flasks keep drinks hot?
Standard vacuum jugs keep drinks hot for up to 12 hours and cold for up to 24 hours.
The material makes the biggest difference. High-quality vacuum flasks with a mirrored glass liner keep drinks hot the longest. Jugs with a stainless steel liner usually don't hold the temperature for quite as long. Find out more about the pros and cons of each material here.
Other factors also affect how long drinks stay hot. Vacuum jugs should be filled completely. The more air there is inside, the faster the liquid loses its temperature. So choose the right size when you buy.
"Preheat your vacuum jug with hot water before pouring in your drink. That way, coffee and tea stay hot for a long time. For a cooling effect, use cold water." – Kerstin, interior expert
2. Materials: stainless steel or plastic vacuum flasks
The outer casing: stainless steel or plastic
Plastic vacuum flasks (1) are lighter, sometimes less expensive and come in bright colours for an individual look. Vacuum flasks with a stainless steel casing (2) are sturdier and more robust and have a refined look.
The liner: glass or stainless steel
Glass insulates better than stainless steel, as it doesn't conduct heat or cold well and the mirrored coating on the inner wall also reflects heat or cold radiation.
Modern vacuum flasks often have a liner made of unbreakable stainless steel. Metal doesn't retain heat as well as glass, but its big advantage is its sturdiness. That's why stainless steel is often used for vacuum bottles and travel mugs that need to withstand being carried around.
Bear in mind that a glass liner can break if the flask is dropped. Some vacuum jugs allow you to replace the glass liner if this happens.
3. The right shape for different uses
Vacuum bottles (1): Thanks to their elongated shape, bottles are particularly suitable for carrying in a bag or rucksack. Vacuum bottles for on the go are usually made of robust stainless steel and have a lid that doubles as a cup.
More and more people use travel mugs on the way to school, to the office or for sport. These small mugs are reusable, robust and easy to stow away.
Pump jugs (2): Pump jugs are designed for serving and have a large capacity. A simple press lets you pour many cups one after the other.
Vacuum jugs (3): A design vacuum jug is ideal at home, on the coffee table or at work, as its capacity is enough for several people or for a longer period.
"In terms of design, many modern vacuum jugs can now hold their own against classic teapots and coffee pots, so they make a harmonious addition to a stylish coffee table." – Kerstin, interior expert
4. The right lid
The tilting lid of the EM 77 vacuum jug by Stelton (1) opens automatically when you pour and can be used with one hand. On this design classic, you can swap the lid for a screw top if you like, so the jug can be carried without leaking.
With a classic screw top (2), you open the lid slightly to pour. The lids can usually be removed completely, which makes cleaning easier. You almost always need two hands to open a screw top.
Vacuum flasks should be easy to use. With push-button lids, you can open the jug with one hand. With Quick-Press (3), you open the lid by pressing a button – once before pouring and once after.
A click lid (4), like a push-button lid, opens with a simple click. A classic vacuum flask also has a cap that you can unscrew and use as a cup.
Why do vacuum flasks hiss?
Vacuum flasks hiss when the air inside heats up and expands. Depending on the design, the seal in the lid may not be completely airtight. The air then escapes, causing the hissing sound.
For a quick fix, close the lid completely or unscrew it slightly so that the air can escape more easily.
5. Size and capacity
In general, vacuum bottles are available with a capacity of 0.5 litres and vacuum jugs with 1 to 2 litres. Pump jugs are often even larger, holding up to 5 litres.
Think about how many cups you want to get from a vacuum jug. The capacity of the cups you plan to use also matters. The more you drink, the larger the jug should be, so that it can fill enough cups.
Drinks cool down faster in a vacuum flask when there is air in it instead of hot coffee or tea. So if you only fill the jug halfway because you don't need much, your drink won't stay hot for as long. That's why it's worth choosing a vacuum jug in the right size for you when you buy.
6. How to clean your vacuum flask properly
Why can't vacuum flasks go in the dishwasher?
Vacuum flasks are usually not dishwasher safe. So don't clean them in the dishwasher or submerge them in water when washing up. If water gets into the vacuum between the inner and outer casing, the vacuum flask may be damaged.
Even so, cleaning a vacuum jug is usually straightforward.
After every use
Rinse the vacuum jug with warm water after use and stand it up to dry.
For light residue or heavier dirt
For a more thorough clean, dissolve a little table salt or baking powder in hot water and leave it in the jug for several hours. For stubborn dirt, or to remove coffee smells and flavours, a denture cleaning tablet in hot water can help.
Use only a soft washing-up brush and a little washing-up liquid. After cleaning, rinse the jug thoroughly and store it with the lid open to prevent unpleasant smells inside.
Cleaning the outside
Wipe the outer casing with a soft, damp cloth and then dry it with a tea towel.
7. Summary - what to consider when buying a designer vacuum flask online
• Glass has better insulating properties but isn't as sturdy as stainless steel. Stainless steel is mostly used for vacuum bottles and travel mugs, as these need to withstand being carried around
• Plastic vacuum flasks are lighter and come in attractive bright colours. Vacuum flasks with a stainless steel casing, on the other hand, are sturdier and more robust
• Vacuum bottles are particularly suitable for on the go, classic vacuum jugs work well at home, and large pump jugs are designed for serving
• With push-button, click or tilting lids, you can open the jug with one hand. Screw tops close more securely and are better suited for transport
• Choose the right size from the start, as flasks that aren't completely full don't keep drinks hot for as long. The more air there is inside, the faster the liquid loses its original temperature
• Vacuum jugs are usually not dishwasher safe, so simply rinse them with hot water after each use and stand them up to dry.
Buy design vacuum flasks online at Connox – your benefits at a glance
- High-quality vacuum flasks – originals from top design brands
- Personal support from our customer service team
- Fair delivery costs
- Secure payment thanks to SSL encryption
- Delivery in just a few working days
Shopping advice at Connox
Would you like to buy a vacuum flask online but need some help? Our customer service team is always happy to help. We'll support you with advice while you shop, make recommendations and answer your questions quickly. Then simply sit back and have your chosen item delivered straight to your door.
