A thermos flask is a chrome-plated container used to keep drinks and other liquids hot or cold for longer. Due to its design, the thermos delays the temperature equalisation between the environment and the stored liquid. Inside the thermos is a double-walled glass vessel that reduces heat conduction. In addition, a mirror coating prevents heat loss through heat radiation.
When buying a thermos flask, various criteria should be taken into account. The most important feature is effective insulation, so that the contents are kept warm or cold for a particularly long time. Since thermos flasks are used in everyday life, it is also important that they are robust and unbreakable. The closures should seal well to allow for trouble-free transport. In addition, the thermos should be easy to fill and easy to clean.
To prevent a brownish layer from forming due to coffee deposits in the thermos flask, it should be cleaned regularly. However, it is not advisable to use conventional brushes as their bristles could scratch the delicate material inside the jug. Instead, it is advisable to use special brushes or a dishcloth. Dishwasher tabs, for example, can be used as a cleaning agent. To do this, fill the jug with hot water, add a tab, let the solution soak in and then rinse the jug thoroughly. Baking soda or vinegar are also suitable for removing deposits from the thermos.
The length of time a thermos jug will keep its contents warm depends on the model and its insulation capacity. Most thermos flasks can keep coffee warm for about five hours, some models even up to ten hours.