Great invention of mankind - a thermos - a real help in everyday life: in a campaign to seize and fresh food in the hospital recovering carry, and to work, a trip, a business trip with him to take. The table and the house is always at hand, all the food, drink a piping hot, keeps the warmth of the soul mistress. How to choose a thermos that he had long held the heat or cold? You need to know a few simple rules.

Who invented the vacuum flask

Thermos for a little more than a hundred years: in 1892, the Scottish scientist James Dewar perfected already invented Veynholda glass box, which was intended for long-term storage of hot or cold substances. Physicist turned Container double-walled flask with a narrow neck to reduce the evaporation of the liquid, silver interwalled space and pumped the air out of him. Thanks to the invention, the first Dewar was able to obtain and retain liquid and solid hydrogen.

For economic use of Dewar first time in 1904 began to apply the German company Thermos (Thermos GmbH), which exists to this day, releasing the best in the world thermoses. Their motto is impressive: "Keep warm. Since 1904 ". Interestingly, the German name of Dewar as the inventor of the thermos is not recognized. Reinhold Burger, a German scientist, a disciple of the Scot, a manufacturer of glass instruments, issued a US patent for its name in 1907, as the inventor of "the vessel with double-wall vacuum between them." Since then, it took many years, but the thermos has undergone very little change. For a long time the name became a household word, although in some countries it is still a registered trademark.

Basic rules of selection

Before you buy a thermos, you must define the purpose. If thermos will have to play the role of guardian of heat or cold on long hikes and trips, it is best to opt for full metal instrument. If the purpose of use - brewing teas and herbs at home, you can buy a cheaper counterpart in a plastic case with a glass bulb. For hot or cold drinks better choice - a thermos with a narrow neck, as he slowly will give heat or cold. With button, a tube or a conventional cap that needs to be unscrewed, any modification thermos permanently retain the desired temperature.

For stationary use, at home or in the office, will serve as a great pump-action thermos, which has a special lever, actuating a pump device. Transportation for this home assistant is undesirable, it is quite massive and heavy. For solid food and first courses are suitable thermos with a wide neck, from which you can easily remove the hot soup or meatballs Cutlets: a variety of national cuisines . This representative of a large family Dewar has one feature: it stores heat longer homogeneous and uniform meals, ie porridge or soup to be hotter than stew, or pancakes, because it is better to pour the hot sauce and then tighten the impressive cover.

There is also netonuschy thermos, the so-called floating, specially designed for boating, water sports, or fishings. It thanks to a special device foods remain even when filled thermos afloat, will not go down. Universal thermos perfectly combines and a thermos for drinks, and the vessel for the first and second courses. The neck is equipped with such dishes so that unscrewing the large cover, it can also put a solid food, and opening the narrow neck - pour drinks.

How to check the quality

Thermoses come with a glass bulb and a completely metal. Glass flasks longer retain heat, but more fragile, metal, made of stainless steel, more durable. Before choosing a thermos, you must read these instructions carefully, and find the address of the manufacturer. Lack of information - an alarming signal, better to abandon such purchases. In the instruction it is important to find a list of equipment and check its availability.

Quality begins with the study of appearance, structural integrity, absence of chipping, cracks, dents. The second step - verification of integrity, for this you need a thermos tightly and shake if no cap or cork, or the bulb does not emit any sound, so long thermos will keep the set temperature. The third step - it is necessary to examine the inner content of the thermos, for this you need to open the lid, remove the stopper the flask and smell: the pungent smell is an indication that the device is made of substandard materials and safety in the food it can be questioned.

At home, you can check the thermos empirically by pouring boiling water into it cool and tightly closed plug and cap. If for 15-20 minutes, the temperature of water is not changed, so the device can serve for a long time. If the body is hot thermos while, experience a failure, it is time to return to the store thermos. In a qualitative device may become warm only cover the body at the same time must always be the ambient temperature.

Jeanne Pyatirikova

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