A thermos is a practical tool designed to keep drinks hot or cold for hours. With these advantages, the thermos is ideal for everyday use because of its comfort and efficiency in one easy-to-carry package. Made from quality materials such as stainless steel with a double vacuum layer, the thermos keeps your drink at the desired temperature, even when carried outdoors.
However, a thermos that is used continuously can experience quite annoying problems, such as the appearance of black crust on the inside. This black crust is usually formed from drink residue, dirt, and mineral deposits from water left in the thermos. If left alone, black crust can affect the taste and cleanliness of the drink stored inside.
However, this problem not only reduces the comfort of using the thermos, but also has the potential to affect the user's health. Black crust that accumulates can become a breeding ground for dangerous bacteria and microorganisms. If not cleaned regularly , a flask full of scale can become a source of contamination which has a negative impact on health.
Unfortunately, even now, there are still many people who are confused about cleaning thermos bottles, especially if they are crusty. It takes a brush and special cleaning agent to make the crust really come off. Luckily, an Instagram user @nichaluthfiah once shared a simple trick for washing a thermos full of black crust.
Through one of the uploaded videos, he admitted that he only used one simple ingredient. Reported by BrilioFood from Instagram @nichaluthfiah on Tuesday (30/7), the simple ingredient in question is citrus.
 Instagram/@nichaluthfiah
How to use it is quite easy. First of all, boil water in a pan until it really boils. After that, pour boiling hot water into a thermos. Only then add enough citrus.
 Instagram/@nichaluthfiah
Next, close the lid and shake the thermos so that the citrus inside can dissolve. If so, let it sit and soak the thermos for 1-2 hours. A mixture of citrus and hot water can help remove stubborn black crust in the thermos.
 Instagram/@nichaluthfiah
After 2 hours, the crust in the thermos will mix with the water. You can open the thermos and throw away the water inside. You will see black crusty bits and fine grains mixed with the water.
 Instagram/@nichaluthfiah
If so, then wash the inside of the thermos using a brush and dish soap. Finally, rinse until completely clean under running water. That way, the thermos will shine again and be more hygienic to use. Basically, citrus or citric acid is a natural ingredient that is effective for removing black crust on thermos because it has strong acidic properties. This acidic property allows citrus to dissolve and break down mineral deposits, stains and dirt that form black crust. Apart from removing scale, citrus is also effective in eliminating unpleasant odors that remain in the thermos due to the remains of the drink being absorbed by the scale. Well, citric acid helps clean and freshen the thermos, so that the drinks stored in it are not contaminated by odors.