New chemical clues emerge for the unique sound of Stradivari violins

Enlarge / A 1729 Stradivari called "Solomon, Ex-Lambert" exhibited at Christie's in New York in March 2007. Don Emmert/AFP/Getty Images

Musicians and music lovers have long appreciated the sonic richness of the violins created by Antonio Stradivari, especially at the dawn of the 18th century (the so-called "golden period"). Scientists have also been fascinated by why Stradivari violins seem to sound so much better than modern instruments; it has been an active area of ​​research for decades.

A recent paper published in the journal Analytical Chemistry reported that nanoscale imaging of two such instruments revealed a protein-based layer at the interface of wood and varnish, which may influence the natural resonance of wood, and hence the resulting sound. Meanwhile, another article published in the Journal of the Acoustical Society of America showed that the better resonance of older violins produces louder combined tones, which can also affect the perception of musical tones.

I've written extensively on this topic in the past, and you can read a handy summary of some of the research in this area to date here. According to my 2021 article, the unique (perceived) sound cannot simply be due to the geometry of the instrument, although Stradivari's geometric approach has given us the characteristic shape of the violin. One hypothesis is that Stradivari used alpine spruce that grew during a period of unusually cold weather, which brought the annual growth rings closer together, making the wood unusually dense. Another popular theory concerns the varnish: that Stradivari used an ingenious cocktail of honey, egg whites and gum arabic from sub-Saharan trees, or perhaps salts or other chemicals.

>

It is the polish that has received the most attention in recent years. The theory dates back to 2006 when Joseph Nagyvary, professor emeritus of biochemistry at Texas A&M University, made headlines with an article in Nature claiming that these are the chemicals used to treat wood - not necessarily the wood itself. - who were responsible for the unique sound of a Stradivarius violin.

Specifically, these were copper, iron, and chromium salts, all of which are excellent wood preservatives, but may also have altered the acoustic properties of the instruments. He based his findings on studies using infrared spectroscopy and nuclear magnetic resonance to investigate the chemical properties of the panels of several violins (the panel is the instrument's largest resonant component).

Further evidence in favor of Team Varnish comes from a 2016 study by researchers at the Swiss Federal Laboratories for Materials Science and Technology (EMPA). They studied how the chemical composition, thickness and degree of penetration of a varnish into the wood affected the acoustics of the instrument. Researchers have found that all varnishes increase the damping capacity of wood, that is, its ability to absorb and stop vibrations...