The thermos is almost in each family, and all know rules of the treatment of him. However not to the superfluous will remind of features of operation of modern thermoses with various systems of covers most long to keep them in a condition of qualitative heatsavings. For some recommendations though are simple, but them quite often neglect. 
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Before each use I recommend to rinse an internal flask of a thermos with warm water for removal of residual smells. It is one of actual problems today which it is however simple to eliminate, having taken as a basis the following simple recipe. For elimination of a persistent unpleasant smell fill up in a flask of 2-3 tablespoons of soda, add up to the top boiled water and let’s settle 20-30 minutes after that merge contents of a thermos and again rinse it.
Store a thermos the open. This council only seems simple. Cases when washed out, but not dried thermos densely closed a cover are frequent; then it is very difficult for opening. And when opened – it was necessary to eliminate an unpleasant smell.
After long operation some hostesses notice on a flask (in a thermos) a white raid or white spots. It occurs because of action of the mineral substances containing in water. 5 %-y solution of vinegar or lemon juice in this case will help. If spots did not manage to be washed in the simple way, fill a product with hot water in temperature of 70-80 degrees Celsius with addition of 1 teaspoon of baking soda and, having densely closed a cover, leave for the night. After that merge contents, carefully rinse and wash up a thermos.
Ugly raid from tea and coffee which appears on an internal surface of a cover of the thermoses which are long in operation, it is easy to remove by means of any modern liquid detergent with insignificant addition of soda. Also do not forget that the thermos can be spoiled, if to its cleaning to apply abrasive washing substances.
For the same reason I recommend to apply a wooden or plastic spoon (from firm, qualitative plastic, not disposable) to hashing in a flask of tea, coffee, herb infusions and other drinks. Metal spoons can scratch a surface of a heatsaving-up vessel from within.
(Including an artificial ice), a brine, the sour and aerated drinks, and also the heated oil it is necessary to exclude flask filling by ice, if you want to keep the thermos serviceable a long time.
Many use a thermos for preservation of heat of hot drinks within several hours or food – when the thermos is specially intended for food and has a wide throat. But on functional features of the thermosaving-up device it can be applied and to cold preservation.
Before application to destination fill in in a thermos hot or cold water (depending on temperature of liquid/food with which will fill a thermos), close a cover and leave for 3-5 minutes. It is necessary in order that the temperature of walls of a flask became approximately to equal temperature of contents of a thermos, differently the flask will take away on itself a part of heat of the product placed in it.
The usual thermos for the household and tourist purpose, having one flask, the average price, at observance of recommendations of the producer keeps temperature to 60 degrees Celsius within 8 hours. That is if boiled water is filled in, it is obvious that after 8 hours of storage its temperature should not in a good thermos fall below 60 degrees. It not maximum, namely average requirements to household unspecialized products of wide consumption.
That drinks or food most long kept heat, it is recommended to fill with them all volume of a thermos. Fill a thermos so that air inside remained as little as possible, but thus there was a place for installation of an internal cover, and contents thus did not spill too much. Then it will more long keep heat.
Always screw up against the stop an internal cover of a thermos. All thermoses with different systems have such cover: and where only the screw cover, and that have both a screw cover, and additional push-button system is provided. Thermoses with a stopper almost did not remain, but their consideration and is not meaningful, as there everything is extremely clear: for the best preservation of heat in a flask it is necessary to establish most densely a cap stopper in a thermos mouth. To exclude course in thermoses with push-button system, track, that the button was established in situation (closed) "is closed". For check of it it is enough to overturn for some seconds a thermos a mouth down. Also for achievement of the minimum losses of heat put on a thermos an external cover and a cover – where it is provided.
All details of a thermos, including stopper of an internal cover of push-button type, wash only manually, having provided situation "is open" in push-button system. For the period of drying a cover of a thermos do not close. In the same "open" situation also store a thermos.
Regardless of that thermoses from stainless steel seem strong, I do not recommend to check specially in practice this circumstance. Cases when after blows of the case of a thermos about external obstacles (generally at transportation), owing to even insignificant dents on the case of thermoses from stainless steel, they lost thermoinsulating properties are in practice known.