Project (2013-2014)

Chemical Knowledge and the Armourers’ Art

The suit of plate armour appeared (uniquely) in Europe in the fourteenth century and remained in use for war and sport for three centuries. Armourers were not simply unlettered village craftsmen but systematic practitioners of applied chemistry. The production of steel required an empirical knowledge of the operation of furnaces to produce the desired product. Heterogeneous though this product might have been, a consistent outcome for the manipulation of its properties to combine hardness with toughness required accurate control of temperature and time. Its decoration involved both the availability of mineral acids to etch the steel and knowledge of displacement reactions, because steel cannot be directly gilded but must be coppered first.

Written accounts of steelmaking or its heat-treatment are seldom informative, because craftsmen are strongly motivated to preserve trade secrets. The sale of recipes only appears to take place after their utility has passed away, and sixteenth-century printed books are full of recipes that were deliberately misleading or incomplete, so our determining the original procedures must depend upon the results of artefact analysis. Nevertheless, although it might have been thought that the world of these craftsmen who practised chemical technology did not impinge upon the Medieval scholastics who wrote about alchemy, there are several cases where the scholastics were evidently aware of developments in ferrous metallurgy; in particular the availability of crucible steel from the Orient, and the production of cast iron in the blast furnace was known by the fourteenth century.