About us

Vacuum flask: History, structure and user’s guidance

October 2nd, 2023

A vacuum flask (also known as a flask, Dewar bottle or flask bottle) is a household appliance used to hold boiling water, ice, liquid from beverage to food to objects that need to be preserved. The vacuum flask is designed to store stuff at a temperature above or below the ambient temperature. This article will show you how a vacuum flask is going.


The vacuum flask was invented by Scottish physicist and chemist Sir James Dewar (1842-1923) in 1892 following an improvement from Newton's calorimeter barrel. Since Newton's machine was bulky, with many parts, it was difficult to preserve and clean it under laboratory conditions. 

For accurate testing, the calorimeter requirement is maximum isolation between the internal temperature of the vessel and the outside environment. Sir Dewar built a type of vacuum flask capable of thermal insulation initially as laboratory equipment.

But Dewar's vacuum flask design quickly became a commercial item in 1904 by Reinhold Burger and Albert Aschenbrenner, two German glass carvers who found that it could be used to retain the temperature of cold or hot drinks.

A vacuum flask design.


A vacuum flask is made from two parts: the inner part and the shell. The shell is cylindrical, its height depends on the shape and size of the plug. The cover can be made of plastic or metal and comes with each type of cover (plastic flask with threaded plastic cap, metal flask with wooden lid). 

The flask cap prevents heat transfer of the flask with convection, and also prevents water from overflowing. The top of the poster also has a handle for convenient transportation, the body of the poster carries the brand name (or decoration). The bottom part can be removed and installed, inside there is a small rubber pad that is used to fix the plug.

The core of the flask is actually a two-shell flask, connected at the mouth, made of silver-coated glass to radiate the heat rays back to the water in the flask. Between the two layers of glass is a vacuum that blocks heat transfer. The bottom of the flask with vacuum holder is the place where the air is drawn between the two layers of the flask. It helps retain within six hours 70 degree C of water out of 100 degree C.

Vacuum flasks with various artworks designed by Rang Dong.

How to preserve the flask

The vacuum flask needs to be rinsed thoroughly before the first use. For a newly bought flask, we need to pour warm water in about 30 minutes in advance, only then comes the boiling water to avoid breaking the flask. However, it should be noted that, if the plug is broken, the water may contact the silver layer, affecting the purity and not good for health. 

If water cools quickly, it means the flask may have been damaged. Silver flakes may be flowing in the water poured from the flask, and cracks can be seen inside.

Using vinegar to clean the flask

In this case, the plug should be replaced immediately. If a plug is used for a long time, we could use hot vinegar to clean it by pouring into the flask, cover it tightly, shake gently and soak for about 30 minutes. Then pour out and rinse with water. The flask should be placed outside children’s reach to avoid accidents. 

In case the water source in the area is contaminated with substances such as Calcium or Magnesium,  sedimentation deposits will appear at the bottom of the flask. In that case, vinegar or lemon can be used to remove them. 

Should you have any questions, wish to share your ideas about vacuum flasks or request a quotation, please send us an email to: export@rangdong.com.vn.

Our website: vacuumflask.rangdong.com.vn

Relevant news
Five key facts about glass refill in a vacuum flask
October 2nd, 2023
Five key facts about glass refill in a vacuum flaskFive key facts about glass refill in a vacuum flask

Many thermos users may wonder about the structure and principle of the glass refill for vacuum flask, what is the best type or if the black dots visible on the surface of a glass refill are going to affect our drinks. Let's check the following facts of a glass refill to see if these factors have any impact on the quality of the vacuum flask or the beverage kept inside.

Rang Dong’s most impressive vacuum flask
October 2nd, 2023
Rang Dong’s most impressive vacuum flaskRang Dong’s most impressive vacuum flask

RD-1045 N1.E is the most favorite vacuum flask with dominant features and durability. Millions of customers have been impressed at the first sight and they are willing to pay money to own it. The product is popular in the Middle East, American Latin and Southeast Asia. Let’s go to this article for discovering the reason why people like this flask so much.

A vacuum flask reduces heat loss to preserve hot drinks
October 2nd, 2023
A vacuum flask reduces heat loss to preserve hot drinksA vacuum flask reduces heat loss to preserve hot drinks

In general, the human blood temperature is at around 37 degree Celsius and we always keep it stable, just to survive. The task for a vacuum flask is also to keep a stable temperature for the liquid it stores inside, and in order to do that, it has a special design to help reduce the heat loss. It is very simple and effective, but how does a vacuum flask reduce heat loss?

Special features make Rang Dong’s vacuum flask stand out
October 2nd, 2023
Special features make Rang Dong’s vacuum flask stand outSpecial features make Rang Dong’s vacuum flask stand out

Rang Dong is proud to be Vietnam’s leading manufacturer of vacuum flasks, which account for 85 percent of Vietnam’s market. With more than 60 years of experience in vacuum flask production and having mastered technology, the company is confident in making every new product that can win customers’ trust.

History of Rang Dong’s vacuum flask production
October 2nd, 2023
History of Rang Dong’s vacuum flask productionHistory of Rang Dong’s vacuum flask production

Since Rang Dong’s establishment in 1961, the vacuum flasks produced by the company have become an indispensable item in many families in Vietnam’s northern region and later, nationwide. “Rang Dong” is now a familiar and reliable brand in the country of more than 90 million people.