A relatively unnoticed or unused item in many of today’s insulated and heated homes, but for people in lesser-equipped houses, colder climates, or outdoor activities in the winter months, a thermos flask can be key to keeping that refreshing hot drink at a toasty temperature, and keep cold drinks… not frozen, with any drink now able to be taken in as fresh as when it was made. Who came up with this small and portable, yet powerful insulator for liquid?
The answer is James Dewar, a physicist and chemist from Scotland, first came up with the idea of the ‘vacuum flask‘ (also known as the ‘Dewar flask’ at the time) in 1892. After a German scientist Reinhold Burger made a similar discovery, that it could keep hot drinks warm, he created a company to sell the flasks (it would be sold on a few years later) starting in 1904 under the company name of Thermos GmbH, the only trader of the device at the time. The business soon took off with the public, and due to its unique brand name, adopted the flasks to be known as ‘thermos’.
The product would be the recipient of several innovation-based awards, and the company grew its invention to test new materials, sizes, and purposes (such as a food jar). As well as being a crucial drinks-carrying device for the British military during World War II, the flask would also be used in scientific experiments for atomic energy. The product would continue to grow, and now can be used to maintain the condition of, and transport important medical material, such as blood transfusions, amongst a wide range of uses.
Today, thermos flasks are made from either plastic, metal or glass, and with the use of hollow walls and a vacuum-based insulator, any possible heat transfer is prevented when the cap (which often doubles as a drinking cup) is on. The video below from German TV (audio in English) demonstrates the basic function of the product, and the history of it in Germany: