The origins of the modern Thermos flask can be traced back to the laboratory of Sir James Dewar, a 19th Century Scottish scientist, where he experimented with low-temperature materials. Producing liquid oxygen at temperatures below -183 C, the problem of storage proved particularly challenging and in 1892 Dewar developed his own solution, the vacuum flask.
His invention consisted of two glass-walled chambers separated by a vacuum, which prevented air currents from moving heat in or out and a silver coating created a reflective layer to reduce additional transfer of heat by radiation. Dewar built on his sub-zero expertise, becoming the first person to produce liquid and solid hydrogen and then to co-invent cordite, a smokeless gunpowder. Eventually knighted in 1904 in recognition of his significant contributions to science, the full potential of his vacuum flask had yet to be realised.
Meanwhile, Rheinhold Burger, one of Dewar’s former pupils, realised that the vacuum flask might have commercial applications. He improved on the fragile design by enclosing the glass chamber in a robust metal casing, secured with protective rubber mountings and in 1904 he sold the idea to a German company of glassblowers. Such a novel invention deserved an impressive name and a competition was soon launched to find one. The eventual winner, a resident of Munich, could never have guessed that his choice would still be a household name in the 21st Century. Derived from the Greek word for heat, “therme”, the Thermos flask had arrived.
Initially, production proved slow and expensive as each glass vessel was hand-blown by skilled craftsmen and only a small number of flasks could be completed in a day. Despite this Thermos expanded, becoming an international concern and in 1911 a London-based subsidiary made an important breakthrough in the mechanisation of flask production. Output increased, prices fell and the vacuum flask became a must-have item with its miraculous claim to keep fluids hot for 24 hours or cold for three days.
An intensive marketing campaign declared it “the bottle of the 20th Century made for up-to-date people” and “a necessity for every modern household from Pole to Pole.” Endorsed by Earnest Shackleton on his trip to the Antarctic and the Wright Brothers in their aeroplane, the Thermos was taken on many famous expeditions, increasing its status even more.
As the flask increased in popularity, new products became available including the classic pint-sized “Blue Bottle” and the “Jumbo Jug,” a gallon-sized jar for storing food. The development of stronger Pyrex jars in 1928 led to the creation of huge 28 gallon containers. These were used in shops as ice cream cabinets or to store frozen fish although commercial refrigeration took over in the 1930s.
World War II brought big changes for the Thermos Company in Britain. Nearly all its resources were directed towards military demands as the vacuum flask became standard wartime issue. It has often been claimed that every time a thousand bomber planes went out on a raid, over 10,000 vacuum flasks went with them. A former pilot recalls how provisions were scarce but, “my kit always consisted of Thermos flasks of tea and coffee and packs of sandwiches.”
Even today, it appears to be valued by servicemen, worldwide. A soldier, recently on duty in Afghanistan, describes how the Russians customise their Jeeps. “Commanders make them plush -fitting curtains, quilted seat covers, fans and drinks cabinets (always containing a Thermos flask of black tea).” After the Second World War production refocused on civilian requirements and the population seemed keen to renew its acquaintance with the pint-sized miracle.
Already established as a domestic favourite for the storage of food and drink, the Thermos flask had wider implications for science, medicine and technology and its list of applications continued to grow through the second half of the century. Its insulating properties proved critical in the field of medicine as it provided an ideal medium for the transport of insulin, human tissue samples and eventually donor organs. Vacuum flask technology has also been applied to aircraft instrumentation, weather detection equipment and is used in the nuclear power industry and international Space programmes.
In a rapidly developing world, this innovative product has worked hard to keep up with current trends and establish itself as a 20th Century icon. As cheap flights made travel more accessible and new technology led to extreme sports, the introduction of the first stainless steel vacuum bottle in 1966 ensured that the flask could meet the demands of a new generation of adventurers. With environmental issues on the agenda today, the obvious energy saving benefits may hold the key to its survival for another century.