Stradivarius violins are highly prized collector’s items. According to some musicians, they produce elegant music with a level of clarity that is unparalleled by modern instruments. And it’s the finishing touches — mysterious treatments applied hundreds of years ago by Antonio Stradivari — that contribute to their unique look and sound. In a step toward unraveling the secret, researchers report on nanometer-scale imaging of two of Stradivari’s violins, revealing a protein-based layer between the wood and varnish. The study was published on October 17 in ACS’ Analytical Chemistry.
A Stradivarius is one of the violins, violas, cellos and other string instruments crafted by members of the Italian family Stradivari, particularly Antonio Stradivari, during the 17th and 18th centuries. They are highly prized as extremely valuable collectors items and commonly regarded as some of the finest instruments ever constructed.
It was reported in previous studies that some stringed instruments built by Stradivari have a hidden coating underneath the shiny varnish. By filling in and smoothing out the wood, this coating would influence the wood’s resonance and the sound that’s produced. Knowing the components of this film could be key to replicating the historic instruments in modern times. So, Lisa Vaccari, Marco Malagodi, and colleagues wanted to find a technique that would determine the composition of the layer between the wood and varnish of two precious violins — the San Lorenzo 1718 and the Toscano 1690.
Using synchrotron radiation Fourier-transform infrared spectromicroscopy, a technique previously used on historic violins, the research team discovered that both samples had an intermediary layer. However, this method couldn’t differentiate the layer’s composition from the adjacent wood.
Next, they turned to infrared scattering-type scanning near field microscopy (IR s-SNOM) to analyze the samples. The IR s-SNOM apparatus includes a microscope that collects images tens of nanometers wide and measures the infrared light scattered from the coating layer and the wood to collect information about their chemical composition. The results of the new method revealed that the layer between the wood and varnish of both instruments contained protein-based compounds, congregating in nano-sized patches.
Because IR s-SNOM provided a detailed 3D picture of the types of substances on the violin’s surface, the scientists say that it could be used in future studies to identify compounds in complex multi-layer cultural heritage samples.
Reference: “A Nanofocused Light on Stradivari Violins: Infrared s-SNOM Reveals New Clues Behind Craftsmanship Mastery” by Chiaramaria Stani, Claudia Invernizzi, Giovanni Birarda, Patrizia Davit, Lisa Vaccari, Marco Malagodi, Monica Gulmini and Giacomo Fiocco, 17 October 2022, Analytical Chemistry.
The authors acknowledge CERIC-ERIC and Elettra Sincrotrone Trieste for access to experimental facilities and financial support.