If you often use a thermos, regardless of the season, then you have most likely noticed a dirty film inside.
The reason for its occurrence is tea, coffee and other drinks that have been in a thermos.
Regular dishwashing detergent does a poor job (if not completely) of removing dirt – after such washing, stubborn deposits remain virtually untouched.
In this regard, the question arises: what needs to be done to achieve perfect cleanliness?
In fact, the solution to this problem is very simple and has long been known to experienced housewives.
It turns out that in order to get rid of plaque, you need to pour two or three tablespoons of citric acid into a thermos (the exact amount depends on the size of the thermos) and fill it to the brim with boiling water.
Leave the thermos for 8-10 hours, or better yet, overnight.
When the morning comes, drain the water, wash the thermos with a sponge with a drop of detergent, then rinse with clean water and enjoy the result - only a memory will remain of the plaque.