Secrets of India’s master sword-makers revealed

Friday 13 February 2015

ISIS scientist Dr Francesco Grazzi setting up the ENGIN-X measurements

ISIS scientist Dr Francesco Grazzi setting up the ENGIN-X measurements (Credit: STFC)
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The skilled craftsmanship that produced pure, strong steel for Indian swords has been revealed in new tests carried out at STFC’s ISIS pulsed neutron source in Oxfordshire. The ISIS instruments were able to study the metal without needing to damage the sword by taking samples.

Scientists and conservationists from the UK and Italy teamed up to examine a 75cm-long, curved single-edged Indian sword, called a shamsheer, that is more than 200 years old.

They used two methods of testing the sword – metallography, which tested the composition of the metals used, and neutron-diffraction, a non-invasive technique using STFC’s ISIS to shed light on the forging process and the materials used.

The antique sword, which is from the Wallace Collection in London, was tested by scientists using two ISIS instruments – INES, which focuses on material science, archaeometry and detector tests, and ENGIN-X, which is more commonly used to test major engineering components such as aircraft wings or train wheels. INES was used to determine the composition and microstructure of the metals used; and ENGIN-X showed how the steel was formed to distribute strain on the blade.

INES Instrument Scientist, Dr Antonella Scherillo, explains. “Our analysis showed that the blade is made of very good quality, high carbon steel with few impurities. We were able to see that, when it was shaped, the metal was allowed to cool slowly rather than being plunged into water. And the methods used to forge the blade were different in the upper and lower parts to make it strong in battle.”

The team established that the steel used is quite pure. Its high carbon content shows it is made of wootz steel, which has a specific band-like pattern. This forms when craftsmen allow cast pieces of metal to cool down very slowly, before forging them at low temperatures.

Dr Joe Kelleher, Instrument Scientist for ENGIN-X, said, “The STFC ISIS team has been able to reveal more information on raw material and production techniques used to forge the shamsheer by applying Time-of-Flight neutron diffraction analysis. Neutrons are an invaluable tool to perform such a compositional and microstructural characterization in a non-destructive way, thanks to their high penetration power into the metal. It was interesting to apply these techniques to something as old and valuable as the sword compared to the major engineering projects we are normally involved with.”

"Ancient objects are scarce, and the most interesting ones are usually in an excellent state of conservation,” said Eliza Barzagli from the Institute of Complex Systems and the University of Florence, who led the research. “Because it is unthinkable to apply techniques with a destructive approach, neutron diffraction techniques provide an ideal solution to characterize archaeological specimens made from metal when we cannot or do not want to sample the object."

Joe Kelleher added, “Warfare has been a significant driving force for the development of materials and other technology throughout history, just as it is today. Experiments like these are necessary to study the history of science, and to learn what technology was known at different points in history and different cultures. The craftsmen often did not record their methods and in some cases actively protected their trade secrets”.

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