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D - 6: When Bronze Casting and Metal Trading had a Second Wind

Updated: Mar 26, 2021

Many years ago, I travelled from Rome to Bologna to see all of Michelangelo’s master pieces. The trip started in Rome where you find most of his work. The Sistine Chapel, the Pieta in the St Peter’s Basilica, his Noah on Pope Julius II’s tomb in San Pietro in Vincoli, the Capitoline Hill, the Dome of St Peter and the façade of the Villa Farnese. It continued to Siena, then to Florence and ended in Bologna – with no work of Michelangelo. But I wanted to see the Basilica of San Petronio, where his 11 foot statue of Julius II stood before it was scrapped.

The Tomb of Pope Julius II with Noah at the Center in San Pietro in Vincoli - would have loved to show the only surviving sketch of Julius II's bronze statue - there is one in the archives of the Rothschild Foundation but it is not published

Yes, you read correctly. When the French led troops kicked the Papal Forces out of Bologna in 1511, they looked for bronze to cast guns. And they found it. Statues got toppled and church bells lowered. Amongst the loot was Michelangelo’s bronze statue of Pope Julius II. In wars, art was and is looted as trophy. We do not need to look further than to the Louvre in Paris or the British Museum in London. They are full of it. But in 1511, It was not the trophy value the troops were after. The war effort required more guns and they were after the metal – regardless of whether Michelangelo’s statue was a treasured piece of art.

Gun technology arrived in Europe sometimes around the 13th century from China where it was in use for already 200 years. European barrels were primitive at first. Made from wood they were held together with iron bands. The name barrel actually stuck and a gun barrel is still called a barrel today. But the design was far from ideal. A wooden barrel could not resist the pressure of gun powder and had to be replaced frequently. Also, it was almost impossible to aim with a wooden barrel. But you could fire a projectile, make a lot of noise and smoke and maybe frighten some horses.

German Bell foundry in the 18th century

The quest for something more solid for making cannons was on. Stone was too rigid and cracked under lateral pressure. Steel could only be made in small quantities, just enough for a harness, a helmet or a sword. There was one large object however, the Europeans knew to cast – church bells. The technology dates back to the 5th century AD when large bell towers became the norm.

Casting bells and cannons have more in common than first meets the eye. Both objects are open on one side and closed on the other. They are hollow inside and have strong side walls. Both have to have the right balance between rigidity and flexibility, otherwise they crack. Both require 100% homogeneous alloys. Bells to produce the perfect sound – vibrations have to travel smoothly through a bells body – cannons to withstand the uneven explosive discharge. It took bell founders centuries to figure out the optimal balance but on the way to the optimum they learned how the varying composition of alloys changes the behaviour of the metal. Bronze weapons in Phoenician times were made with one part tin and nine parts copper, church bells with 80% copper and 20% tin – the softer tin makes them more flexible and the sound rounder.

It did not take long to apply this know-how to casting gun barrels. The casters found that an alloy of 88% copper, 8-10% tin and 2-4% zinc was ideal. Gun metal was born. Sadly, there were only two sources for copper or tin. Mines far away from home – or the bells and bronze statues of your neighbour. Have you ever wondered how much of our art disappeared in these melting foundries? I fear quite a lot. Far fewer bronzes survived from antiquity than marble statues. Did ancient artist prefer marble so much over bronze? I guess putting a question mark here is the right response.

English 18th century bronze cannons by caliber – the classification is by weight of the cannon ball – the cut on the left shows you the similarity with church bells

Of course, you cannot build your entire armament industry on robbing your neighbor. Thus, mining of copper and tin had a second wind. When you travel to Cornwall you will find many old mines which were operated in the 15th to the 18th century. Metal trading had a boost as well and the Genovese played an active role in shipping the raw materials. The geology of Europe had not changed since Phoenician times. Tin mainly came from Cornwall and Copper primarily from Anatolia. The demand for these metals was low for centuries but picked up in the late Middle Ages with the expansion of old and the creation of new towns (=new church bells) and the mass production of bronze cannons. By the 16th century metal trading was again as strategically important as during the Bronze Age.

There is one prominent example in history when the process of melting art for making cannons has been reversed. When in Paris, take the time to visit the Place Vendome – not because Princess Diana loved to stay there at the Ritz – but for the Vendome Column. It is made from 180 cannons captured from Austria and Russia at the Battle of Austerlitz in 1806. The monument was completed in 1810. Napoleon wanted an equivalent to Trajan’s Column to celebrate his glorious conquests. He saw himself as the true heir to the Roman Emperors. The column tells us in pictures the story of his successful 1806 campaign which took him from Boulogne to Ulm and then to Vienna and made him the master of Europe - for a few years.

Napoleon’s column at the Place Vendome

Luckily, no more guns are made of bronze today. There is thus little chance that the column will be melted down. You do not have to rush to visit it. Anyway, there are few visitors who actually have a closer look at the monument. I guess most do not understand its significance. Had it been cast by Michelangelo, am sure this would be different!

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