The Eiffel Tower: did you know it’s not made of steel?

Did you know that the Eiffel Tower, one of the great icons of engineering, is not made of steel?

Contrary to what many people think, this iconic Parisian structure is made almost entirely of puddled iron, a material that was key to the Industrial Revolution and marked a fundamental stage in the history of metal construction.

Used in the 19th century before the popularisation of modern steel, was obtained through a traditional process that consisted of removing impurities from pig iron in special furnaces, stirring the material manually.

This produced iron that was much more ductile, resistant and less brittle than traditional cast iron, which made it possible to erect structures as bold and slender as the Eiffel Tower, inaugurated in 1889 and composed of more than 18,000 pieces assembled with millions of rivets.

At the time the tower was built, steel existed, but it was still expensive and difficult to produce on a large scale. For this reason, puddled iron was the choice for large public works and railway projects. This material is characterised by its low carbon content (less than 0.1%), which makes it more malleable and easier to work with than cast iron, although its production was much more laborious, as it required a great deal of manual intervention.

From the end of the 19th century and, above all, in the 20th century, the emergence of new industrial processes, such as the Bessemer converter and the Siemens-Martin furnace, revolutionised steel production, making it much more accessible and versatile. Modern steel, an alloy of iron and carbon (along with other elements), made it possible to build even taller, lighter and stronger structures, gradually replacing puddled iron in architecture and engineering.

The main difference between the two materials lies in their composition and manufacturing process. Puddled iron is softer and more ductile, but steel is much stronger, more elastic and more durable, allowing structures to be lighter without losing strength. In addition, steel can be treated in different ways to improve its resistance to corrosion and inclement weather, as is the case with the stainless and galvanised steels that we use today at Hierros Mora Antón for our projects.