The focus of this essay is on substitute materials, particularly the research on substitute metals. The two periods of autarky in Germany were of primary influence on this field. Engineers and construction engineers proved most important in this context despite inter-institutional cooperation between the disciplines of metals research, materials testing, and technical mechanics. Engineers had to solve construction problems respecting the materials used and to analyse components in terms of economic efficiency. However, the research on substitute metals not only meant (...) the substitution of one substance for another. It also implied economizing and recycling scarce materials. These activities required tacit knowledge. Engineers succeeded to some degree but the German war economy paid a high price for it. Each technical system demanded a case-specific approach. Typically a loss of effectiveness, reliability and durability of the products containing substitutes had to be taken into account. (shrink)