Answer: with a glass bulb. First, glass conducts heat worse. A simple example: pour boiling water into glass and steel mugs and grasp them with your hands. Steel will begin to burn in a few seconds, and glass much later. This means that metal dishes give off heat to the environment faster.
- Blocking contact with the external environment: The thermos bottle has two walls, between which a vacuum is created.
- Blocking free heat radiation: the walls of the thermos are covered with a heat-reflecting layer of silver or copper.
Secondly, in the manufacture of glass flasks, a better vacuum is created. Yes, the vacuum can be “bad” and “good”. Bad -it is a very rarefied gas, but still. It remains between the walls of metal flasks due to the imperfection of the air pumping technology used for them.
In addition, a crime against the user is committed ... by the very stainless steel from which the cylinders are made. It turns out that most metals absorb gases from the environment, and the decrease in pressure between the walls of the cylinder causes the gases to evolve back. Because of this, the quality of the vacuum deteriorates even more. Some manufacturers, in particular Thermos, use non-standard technologies for the production of metal flasks, which improve their thermal properties.
ON A NOTE
How to test a thermos: pour hot water into it and wait 5 minutes. If the body is hot, the properties of the thermos are impaired.
Which thermos is best for herbal teas
Answer: with a glass bulb. Due to the same property of absorbing gases, metal flasks "fix" the smell after brewing herbs. We know from our own experience that it can get boring. The scent of good Ceylon tea goes better with the scent of fallen leaves than with the harsh scent of some thyme. For anti-cold teas, yoga elixirs and vitamin extracts of rosehip, take a thermos with a glass flask - it is easy to clean.
Which thermos to choose for harsh travel
Answer: with a metal bulb. During extreme travel, a thermos has a decent chance of being firmly attached to something solid. A fragile glass flask will most likely not withstand such treatment, and a thermos with a metal one will get off only with a dent on the body.
Ordinary thermos glass is "afraid" of sudden temperature changes. You can't just take and fill a thermos with a cold glass flask with boiling water - it will crack. At the same time, there are thermoses with cylinders made of special glass resistant to thermal shock. As a rule, manufacturers give them brand names and proudly mention them in the product description.
ON A NOTE
A high-quality thermos will "give out" scalding hot tea after 12 hours of travel. After 24 hours, the temperature of the drink will be about 50 ˚C, if you do not open it before.
What size should a thermos for drinks be
The more tea is “charged” into the thermos, the longer it stays hot. So it is better to take a kilogram of excess weight than to sip on a semi-warm liquid, hugging a cold gun in the middle of a snow-covered forest. But the neck of the thermos should be narrow. The largest amount of heat is lost through it, so food thermoses with wide lids are definitely not suitable for a long journey.
Should you use one thermos for everything?
There are so-called universal thermoses designed for food and drinks. They are large, with a wide lid from which tea or coffee can be poured under pressure. The trouble is that they use metal flasks. Once you pour a bucket of borscht into such a thermos, you will receive tea and coffee with borscht aroma from it for a very long time.And a large lid leads to irrational heat loss. Better to buy two or even three thermos for different occasions.
Keep the tea hot!
