As part of his research into liquid gases, chemist Sir James Dewar invented the Dewar flask, which was the forerunner of the Thermos flask. In order to maintain the low temperatures required to store gases that had been converted to liquids, Dewar employed a double-walled vessel with silver plating. This enclosed a vacuum, keeping out heat and ensuring the liquid gas could be stored for long enough to enable its properties to be discovered. Additionally, in 1898 Dewar was the first to collect liquid hydrogen, which is today used as a rocket fuel. This painting shows the chemist at work with a variety of his flasks. Unfortunately for him, Dewar did not acquire a patent for his invention and from 1904 the German firm Thermos began manufacturing insulated flasks.