It is difficult to do without a thermos during trips and hikes. It is nice to drink hot tea or coffee on the way. In addition, it is convenient to use for brewing various herbal decoctions and infusions. Broths and soups are also poured into the thermos, and in the model with a wide mouth – even second dishes. But in the process of operation, scale appears on the walls, dirt accumulates, and an unpleasant smell appears. Let’s analyze how to wash the inside of a thermos from black deposits. This can be done in various ways, and we will tell you about the safest for the device and the most effective in cleaning.

Reasons for the appearance of black plaque

A thermos is a stainless steel product in the shape of a cylinder, inside which a glass or metal flask is located. There is an air gap between it and the outer walls. The device is hermetically sealed from above with a lid. Thanks to this, the initial temperature of the substance inside is maintained. But during operation of the thermos, plaque, separations, and scale appear.

The main reason is strong brewed tea or coffee. If you pour such a liquid into a thermos, after an hour a brown or black coating will appear on the walls, which is difficult to remove. It is difficult to wash it. The peculiarity of the drink is that it contains a large amount of tannins. These are insoluble particles from tea leaves that simply have nowhere to go, so they settle on the walls of the vessel. The longer the tea is in the container, the thicker the coating. The same applies to the coffee drink.

The second reason for the appearance of plaque is the use of hard water. Tap water usually contains a large amount of iron, calcium, and magnesium. When these elements are heated, they turn into carbon dioxide. It is because of it that a hard coating remains on the walls of the container. Lime scale can be removed in several ways.

But even if you thoroughly wash the flask and neck and do it after each use of the device, it will not save you from the appearance of scale and unpleasant stains. But you can use special improvised means.

How to wash the inside of a thermos from black deposits

The main methods

There are several ways to clean a thermos from the inside of a tea scale. But their use also depends on the material from which the bulb is made – glass or stainless steel. The first material is fragile and requires special care. You can wash the inside of the flask with improvised means that can be found at home.

Using vinegar

You can remove plaque and scale inside the thermos using acids. They are quite aggressive, so they have a negative effect on metals, including stainless steel. But they can be used in relation to glass flasks. For example, vinegar is the best option. You can use both synthetic and natural. The concentration should be approximately 6-9%. Such a tool acts as a solvent. Pay attention to the following:

  1. Pour vinegar into a thermos half or a third of the flask.
  2. Then add boiling water.
  3. Close the flask and leave for 2 hours.

It is allowed not to dilute the vinegar. Then it will take less time to dissolve the plaque. But vinegar essence should not be used. Acetic acid is hygroscopic, so it will additionally collect all bad smells. Drain the liquid and thoroughly wash the walls of the flask.

Lemon, citric acid and soda

The most ecological cleaning of a thermos is the use of lemon. It is necessary to cut the lemon into small pieces, and then place it in the flask. Leave it like that for the whole night. Thanks to this, not only the plaque disappears, but also the unpleasant aroma.

Citric acid is another inexpensive, but effective method to get rid of scale and plaque in a thermos. Pour 2 tbsp into the flask. l. means with a slide and pour boiling water. Then leave everything for several hours or all night – it already depends on the thickness of the layer of black plaque. At the end, it remains only to rinse the container in clean water. If the stains still remain on the walls, the procedure must be repeated again.

Baking soda (sodium bicarbonate) is used as a gentle agent with mild abrasive properties. It is suitable for both metal and glass flasks. This is a fairly quick way to wash the container inside. It is necessary to pour soda powder on a kitchen sponge, and then carefully rub the walls of the container. If the bulb is narrow and long, then it will not be possible to wipe everything in this way, since the hand and fingers will not be able to penetrate inside. In this case, it is recommended to use another method.

To reach the very bottom of the flask, you can use a sponge, pushing the sponge as far as possible. If the plaque is dense and hard, then it will not be possible to deal with it the first time. The procedure will have to be repeated several times. But it is best to start soaking before that.

how to wash a thermos

Application of groats

Oddly enough, you can wash the thermos from the inside using cereal. It perfectly removes plaque in the flask. It is recommended to use rice, pearl barley or peas. They represent a kind of ecological sponge. When they swell in boiling water, porridge with a loose structure is obtained. It cleans various surfaces well.

You need to do the following:

  1. Put a few tablespoons of raw groats in a thermos and pour boiling water over it.
  2. Close the container tightly and leave for an hour. To increase the efficiency of cleaning, add 2 tbsp. l. ordinary baking soda.
  3. After an hour, when the cereal swells, it is necessary to shake the thermos with force, but do not open it.
  4. At the end, it remains to pour out the contents and wipe the walls with a sponge.


Surprisingly, carbonated drinks help to wash the thermos from blackness inside. Many people already know that children’s favorite sweet carbonated drinks, such as Fanta, Coca-Cola and Sprite, cope well with limescale. They are usually used to clean teapots, but you can easily use this simple tool for a thermos as well.

It has been observed that Coca-Cola works best. It removes the layering from tea well. Such drinks contain orthophosphoric acid. It is used in dentistry to bind teeth, and is also used when soldering metal parts. To clean a thermos, you must first boil the drink, and then pour it into a flask and close the container. Then it remains only to wait during the day.

Effective underwear

Sodium hypochlorite, which is popularly known as laundry, helps wash the thermos from any dirt. The product has antibacterial, whitening and disinfecting properties. Its concentrated form should be used with extreme caution. The product contains aggressive chlorine.

It quickly destroys scale and plaque, but at the same time it can also corrode seams, plastic and rubber parts. The thermos, of course, will become clean, but it will no longer perform its functions due to the fact that the gaskets will deteriorate. Because of this, he will not be able to keep warm. That is why it is forbidden to use linen in its pure form to clean the thermos.

It is necessary to dilute the product with ordinary water in equal proportions, and then wet a kitchen sponge in the product and wipe the container from the inside (including using a scouring pad to get to the bottom). The laundry will also remove the unpleasant smell from the flask. After such cleaning, you need to wash the device with soap, and then dry it without closing the thermos. Although for some period the aroma of linen will still be heard, albeit distantly.

how to clean a thermos

Alcohol and baking powder

Ammonium alcohol will help to clean the inside of the thermos. This is a rather aggressive environment that has a caustic aroma. But ammonia will quickly destroy the unpleasant smell from the thermos, remove stains and plaque. But it should be taken into account that if the flask is made of stainless steel, then with prolonged contact of the metal with ammonia, it begins to deteriorate. Experts advise mixing chalk and ammonia in equal parts, and then apply this agent to a kitchen sponge and start rubbing the bulb. The option is suitable for glass surfaces. It is necessary not to soak, but to act as soon as possible.

A great option to clean the inside of the thermos is baking powder, which is used when preparing dough. It contains citric acid and baking soda. Thanks to this composition, the product removes plaque well. To clean the flask, you need 3 tbsp. l. pour baking powder inside, and then pour warm water. Leave the thermos closed for 3 hours. After that, drain the solution, and clean the flask with a rag and a sponge. The procedure can be repeated several times.

Prohibitions during cleaning

To get rid of the black coating inside the thermos, people resort to various tricks. But you need to act carefully and carefully so as not to damage the bulb from the inside. It is forbidden to use the following:

  • metal sponges;
  • stiff hairs;
  • egg shell;
  • sand;
  • cleaning powders;
  • acids with a high concentration.

Such means will quickly damage the surface of the bulb inside. It will be scratched or corroded, it will become thin. Because of this, it becomes unstable. In addition, the thermos ceases to perform its functions well, since it will no longer keep heat for so long. In addition, bacteria accumulate in small scratches. It is difficult to get them out of there. And this is already dangerous for the health of a person who will drink from a thermos.

cleaning the thermos

Preventive measures

In order to prevent plaque from appearing in the thermos, it is necessary to follow a number of rules.

First of all, so that layers do not appear, it is necessary to drink a hot drink as soon as possible. The longer the tea stays in the thermos, the more plaque is formed. It is not recommended to drink yesterday’s tea or to infuse it for more than 15 minutes.

Secondly, it is recommended to use only soft water. It does not contain minerals in large quantities, due to which fatty scale is formed.

Thirdly, you must always dry the thermos after each use and washing. It should never be left with moisture inside, closed or turned upside down. The bulb should be dry. Then an unpleasant aroma will not collect in it, scale will not appear.

How to wash the inside of a thermos from black deposits