From the Greenhouse into the Fighter Bomber: How ‘Metal Paper’ Became the World’s Thermal Insulator

Abstract

When the thermodynamicist Ernst Schmidt in Munich discovered aluminium foil’s properties as a thermal insulator in 1924, he first analysed it under both laboratory and product testing conditions at the polytechnic in Danzig (Gdańsk). The first findings that Schmidt gathered on aluminium foil, concerning its use as a thermal insulation material on a large scale, were gathered when the piping of Dresden’s municipal long-distance heating system was insulated with it. This application of aluminium foil as an insulating material affected energy efficiency in economic proportions for the first time. This contributed considerably towards the establishment of the professional discipline of thermal economics (Wärmewirtschaft) in Germany’s polytechnics at the end of the 1920s and later worldwide. When Schmidt was appointed director of the Institute for Engine Research at the Aeronautical Research Institute in Braunschweig in 1936, besides being involved in the development of liquid-propellant and solid-fuel rockets for military purposes, for the Wehrmacht and the Waffen-SS, he became increasingly occupied with the thermal insulation of those devices. Immediately after World War II, Schmidt was able to continue his research at Britain’s Royal Aircraft Establishment in Farnborough and later on at the universities in Braunschweig and Munich. His academic research particularly allowed him to continue to develop aluminium foils as insulation materials. This paper aims to retrace the path towards the exploration of aluminium foil as a thermal insulation material. It also shows how aluminium foil and its multifarious applications, more than other materials, emerged as a major economic factor in the twentieth century within the context of municipal and state energy economics. Civilian and military research projects that incorporated aluminium foil early on as a thermal insulator are also described.