A thermos can be useful not only in winter, but also in other, much warmer times of the year.
True, in this case, its owner may encounter such a nuisance as a dirty coating - it often covers the inside of the thermos.
The reason is any liquids that get into the thermos: tea, coffee and other drinks.
Regular dishwashing detergent cannot wash away such dirt – after using it, dirty streaks still remain inside the thermos.
If you are still racking your brains over what to wash the product with to get rid of the annoying plaque, there is good news.
Citric acid will help you achieve perfect cleanliness.
It is enough to add 2-3 tablespoons of lemon juice (the exact amount depends on the size of the thermos being cleaned) and pour boiling water inside.
The liquid should reach the edges of the thermos. Leave it filled with cleaning solution for 8-10 hours, or better yet, overnight.
In the morning, pour out the citric acid solution and rinse the thermos with running water. Now you can evaluate the cleaning result - there will be no trace of scale left.