In the information age, it is very easy to not only source building materials online from suppliers with an emphasis on quality but also easy to learn about how the materials you choose to use work and why this is the case.

With this in mind, it can be difficult to conceive of either a building material or a way to optimise an existing construction material that has been lost to time, but there are more cases of lost construction art than you might expect.

For example, flexible, strengthened glass was allegedly invented by a Roman inventor, who after showcasing it to the emperor Tiberius via a drinking bowl that could not be shattered, was subsequently beheaded so as not to lower the value of gold and silver.

Another example that is more tangible but no less impressive is an iron pillar in Delhi, India, which is well over 1600 years old and yet despite this has no signs of corrosion or rust damage, something that is seen as practically inevitable with iron and was at one point so amazing it was associated with extraterrestrial life.


What Made The Iron Pillar Special?

A lot of the origins of the Iron Pillar of Delhi are somewhat unknown, although several surviving inscriptions suggest a potential timeframe for the construction of the pillar as being at some point in the early fifth century.

Yet despite its age and the lack of rust-proofing knowledge and capabilities we have now, the Iron Pillar has survived and endured with far less rust than a lot of modern examples of wrought iron, attracting the attention of metallurgists and historians alike.

It was believed to have been initially constructed outside of the Udayagiri Caves, a shrine that was constructed and developed at a similar time, before being moved to its current location near Mehrauli in Dehli, possibly as a direct result of the city’s founding around 1052 AD.

When it was initially discovered and started to be studied in 1831, it was considered to be an incredibly impressive feat of iron smithing, as it was constructed with an immense resistance to corrosion, leaving a lot of the pillar barely touched by time.

A potential explanation of why was first published in 2000 by R. Balasubramaniam of the Indian Institute of Technology Kanpur posited that the particular construction conditions of the iron, including a high amount of phosphorus, which was traditionally seen as a damaging contaminant in Victorian wrought iron.

Phosphorus can in excessive amounts cause iron to become exceptionally brittle in cold temperatures, hence why it became known as coldshear to ironmongers.

However, by not using lime in the blast furnaces and using wood with high phosphorus content, ironmongers instead helped to create a corrosion-resistant film.

This, in turn, provides a passive resistance to atmospheric conditions, allowing the iron to survive for thousands of years.

Until this discovery, however, the Iron Pillar of Delhi confounded a lot of materials scientists, despite most facets of its construction being well-known and well-established, to the point that author Erich von Däniken believed it was proof of the existence of aliens for years.

This ended when someone politely informed him that despite being impressive, it was rust-resistant rather than rust-free, and was not constructed with methods unusual to the time.