Process of preservation of products contains many and many thousands of years. Even at excavation of ancient Egyptian pyramids canned food which was put together with a sarcophagus of the died Pharaoh were found. These canned food did not lose the nutritious properties though since their burial there passed about three thousand years. Carcasses of birds embalmed special structure, filled in with oil and tightly sealed in clay jugs. Thus, hit of air to canned food was blocked, and they long remained.
France and canned food
Then Napoleon Bonaparte is the emperor of France, for a big reward, suggested everyone to invent a way thanks to which food for a long time would remain. It became in order that in the French army, in campaigns, there was always a fresh food that soldiers were vigorous and also the lack of normal food was the cause of many diseases which literally mowed down soldiers to the introduction them in fight.
Such method of conservation was thought up and still the principle of action did not change. To warm products before boiling (that is to kill all microorganisms which promote decomposition of products) and then to shift them in also sterilized container. Then hermetically to cork and thus the preserved products can be stored very long time.
In our 21 century it is not enough that changed in ways of conservation in house conditions. Products undergo heat treatment, also glass jars are boiled and twist covers.
How to open a jar?
For opening of iron covers from cans the special can opener was thought up. By means of it all canned food perfectly opened, but progress did not stand still and banks with the turning-off covers were thought up. These covers significantly accelerated process of preservation in house conditions, but here to process of opening of the twisting covers on bank there can be problems.
That without efforts to cope with untwisting of a cover, it is necessary to degrease carefully hands and a cover, to wipe them dry. For a good skhvatyvaniye of a hand with a cover food wrap is used.
It is also possible to apply an ordinary elastic band which is put on a cover banks. And the most fascinating: it is necessary to twist not a cover, and to bank, rotating counterclockwise.
Easily it is necessary to open a jar with the twisting cover some sharp object (knife, a fork, the screw-driver), to accurately hook edge of a cover until cotton is heard. It means, air got to sealed to bank and now it is easily possible to open a cover about banks.