Vacuum flasks and bottles to hold hot and cold drinks can be found in almost every household, but few people know that the vacuum flask, otherwise known as a thermos flask, was originally developed to hold liquid oxygen. In 1903, the contract for this went to a gentleman from Berlin called Reinhold Burger and he invented the “thermos bottle,” a double-walled, or lined container that kept the temperature of its contents stable for up to 24 hours. He developed it into a household bottle to keep drinks warm in 1908 and advertised it with the slogan: „ „Hält kalt, hält heiß – ohne Feuer, ohne Eis,“ which means, “keeps cold, keeps hot – without fire, without ice.“ In 1909 Burger sold the patent and the brand name „Thermos“ to Thermos AG in Berlin and the Thermos bottle Company in the USA.
Today the oldest European thermal container producer is the „Helios Dr. Bulle GmbH & Co. KG“ company. It was founded in Ilmeanu in Thuringia in 1909 and has been located in Wertheim since 1950. „Alfi Zitzmann GmbH“, another thermal container producer, which is now part of WMF, the Württemberg Metal works Factory in Geislingen, has also been located here since 1949 – another company that came from Thuringia that was founded in Fischbach in 1914.
Thermal containers are vacuum containers. A vacuum is a hollow space that doesn’t let warm or cold out. Thermal containers are made of two glass flasks placed one inside the other, with an interior mirror coating. The mirror-coating reflects the warmth or the cold back inside and prevents it escaping and was created as a by-product of mirror production - in the same way as the mercury, or „farmer’s silver,“ was used to coat the inside of Christmas tree decorations.