Up until recently, architects credited stonemasons for developing brilliant feats of engineering to create Europe’s great Gothic cathedrals. Experts believed that concrete was the main medium used to hold up structures like Northern France’s Cathedral of Saint Peter of Beauvais. The building, which was begun in 1225, features staggeringly high vaulting, flying buttresses, and an intricate stone facade.
It isn’t that historians have never observed iron reinforcements in Gothic cathedrals before—they can be seen clearly in Beauvais and other structures from the era, and iron has been used sparingly in construction as far back as ancient Greece and Rome. But few thought that such technology was put to work for structural purposes much earlier than the Industrial Revolution. It was assumed that the iron rods and reinforcements visable in Gothic cathedrals were installed by later generations in order to help brace the aging buildings.
Iron was thought impossible to date, but the new process identified tiny traces of carbon left behind when the metal was smelted, allowing the team to carbon-date the actual wood burned to extract the iron from ore.
At Beauvais, the researchers were able to prove that the iron used to hold up the 157-foot-high choir (the tallest ever built in Europe) dated all the way back to 1225, which indicates that it was used in the original construction. The discovery clarifies our understanding of cathedral building techniques and makes the job of a medieval architect look just a little easier.