Antonio Stradivari was an 18th century violin maker. Before he died, his son asked him the secret of his incredibly sounding violins. Antonio's answer was that a really good craftsman should be able to discover the secret by himself. So, the secret was buried with him. Until now.
Joseph Nagyvary of Texas A&M University has been struggling to uncover the Stradivarius secret for the past 30 years and now it appears that he has finally did it. His conclusions are published in the current issue of Nature in an article co-authored with Joseph DiVerdi of Colorado State University and Noel Owen of Brigham Young University.
"This research proves unquestionably that the wood of the great masters was subjected to an aggressive chemical treatment and the chemicals - most likely some sort of oxidizing agents - had a crucial role in creating the great sound of the Stradivarius and the Guarneri," Nagyvary says. "Like many discoveries, this one could have been accidental. Perhaps the violin makers were not even aware of the acoustical effects of the chemicals. Both Stradivari and Guarneri wanted to treat their violins to prevent worms from eating away the wood. They used some chemical agents to protect the wood from worm infestations of the time, and the unintended consequence from these chemicals was a sound like none other," he adds.
Antonio Stradivari made about 1,200 violins, an unknown number of guitars and mandolins and one harp. He was so fond of his violins that he would only sell one when he was ready to part with it. Today, there are only about 600 Stradivarius violins remaining and they are valued at up to $5 million each. There are only two of his mandolins left.
Guarneri del Gesu was a contemporary of Stradivari and, although he is less known to the public, experts consider his instruments equal in quality. Consequently, they have similar prices.
The main obstacle in discovering the secret behind the Stradivarius and Guarneri violins was that they had to do it without destroying the violins! They employed spectra analysis (infrared and magnetic resonance spectroscopy) which can tell you the chemical composition of a material. They analyzed each instrument's backboard.
"This is highly gratifying for me, because it proves what I first proposed 30 years ago - that the chemicals used to treat instruments and not the unadulterated wood itself - were the reasons for the great sound of these instruments," said Nagyvary. "I was criticized and ridiculed when I made these claims, and to have undeniable scientific proof that I was correct is very satisfying, to say the least."
Jon Whiteley, the curator of music at the Ashmolean Museum in Oxford, UK, who owns two of Stradivarius' violins and one of his guitars is still skeptical of the discovery. "The quality of the alpine wood and the varnish is critical of course," he said, "but it's the shape of the resonating soundbox, and the curvaceous, arching way it bows outwards that gives the unique tone."
The shape of the violin is of course important but that might be the easy part to reproduce. The chemical treatment of the wood is also vital because it makes the backboard vibrate in a specific way. Any sound can be understood as a superposition of "resonances" - of simple sinusoid waves having various wave-lengths. The particular resonances involved in a sound give its tone color and the chemical composition of the material is relevant to what resonances are emitted by the vibration of that material. For example, a vibrating metal string gives a different kind of sound than a plastic string. Similarly, a properly treated wood backboard gives a Stradivarius vibration while another backboard gives just a common violin sound.
In 1998, Nagyvary had discovered how to reproduce some of the Stradivarius-like resonances by treating a violin backboard bade of modern maple wood with salt water and grape juice. In 2001, he discovered that he can create an even more similar sound to that of a Stradivarius by adding borax, which is an anti-woodworm treatment Stradivari is likely to have used. "The next step is to identify the chemical agents involved," Nagyvary said. "To do that, more precious wood samples are needed."
They have now discovered that a chemical wood preservative used in timber yards around Cremona in Lombardy, where both violin makers worked, is responsible for the violins' sound quality. The analysis of the wood has shown that it has a different chemical composition to maple grown in the region today. "The great Italian masters prepared their wood by artificial means. The violin backs appear to have been brutally treated with salts of copper, iron and chromium as wood preservers," Nagyvary said.
The reason why Nagyvary said that Stradivari probably discovered his manufacturing process by chance is that Stradivari could barely read and had no scientific training whatsoever. "They would just find salt crystals in local quarries and dissolve them in water - they didn't know what they were throwing in." Nonetheless, he made the most famous violins of all time and his violins still work almost three centuries later, precisely because of the wood preservation technique.
"In the past, there has been a lack of cooperation from the antique violin business, and that has to be overcome. It may help us to produce violins and other instruments one day that are just as good as the million-dollar Stradivarius. And this research could also tell us ways to better preserve instruments, too."