A couple of tablespoons of baking soda should be poured into a thermos and pour boiling water on top. In an hour you need to put in a handful of coarse salt. Instead of salt you can also use crushed egg shells or fine sand. Next, you need to tightly close the thermos lid and thoroughly shake its contents. After this procedure, the inner surface of the flask will Shine like new.
Copes with dark cleaning plaque and citric acid. Enough to fill a tablespoon of it in a thermos and pour boiling water. Next, you need to wait until the water has cooled. If the first time RAID will not depart until the end, then the procedure should be repeated again. Then the inner surface of thermos will definitely become clean and shiny.
You can try to clean the thermos in the following way. You need to fill a quarter of it vinegar, Apple cider, and the rest pour boiling water. The resulting solution should be allowed to steep for a couple of hours. Then you should pour it away and rinse the inner surface of the flask clean with cool water.
There is another way to get rid of plaque. A third of the thermos to pour ordinary white sold in any hardware store. Then fill the thermos with boiling water to the top, close the lid and shake the contents. Using this method from a thermos disappear all kinds of dirt. Naturally, cleared of plaque thermos a few times, rinse with warm, soapy water and rinse.
To get rid of plaque on the inner surface of the flask can be lowered into him a couple of tablets for cleaning dentures, the Gulf of boiling water and leaving for the night. In the morning, simply rinse the flask with clean water and allow to air dry.
Thermos after every use need to be cleaned in hot soapy water. The only way to protect the inside surface from the formation of unwanted plaque.