Materials Engineering of Violin Soundboards by Stradivari and Guarneri

Abstract

We investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions—borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second‐harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

The impact of alkaline treatments on elasticity in spruce tonewood

“…When the combination of pre-treatment and sizing is considered, an increase in the penetration depth can be observed if compared to the direct application of sizes on untreated plates, especially when KOH is applied. This result, together with a reduction of the density in the upper portion of pre-treated specimens, and thus of the equivalent density of specimens, may confirm the action of alkaline treatments as an artificial support in wood drying or aging 2 .…”

“…The surface of the tonewood usually undergoes three main types of treatment during the finishing process. First, the plates are pre-treated with alkaline solutions to enhance wood durability and prevent biological attacks 2 . We will refer to these as pre-treatments .…”

“…Indeed, it is commonly accepted that varnish does not only contribute to the aesthetic appearance of violins, but it also plays an important role in the wood protection 13 and sound production [14][15][16][17][18][19][20] . Conversely, very few works suggested possible chemical compositions for primers and provided a tentative explanation about their function 2,21 . Primers…”

Reviewed Commentary: Factory-Grown Wood, the Future of Forestry?

“…The science that emerges as fiber-based and architectural products are developed could enable growing materials with specific physical, mechanical, and even acoustical properties for musical instruments. Using adulterated wood is not an uncommon practice-Stradivari himself did not rely solely on the properties of maple and ebony, but incorporated borax, zinc, copper, and alum (Su et al 2021). Su et al (2021) have already posited that engineered wood can reintroduce the cellulose rearrangement and hemicellulose fragmentation created by famed Cremonese violin makers of the 1700s.…”

“…Using adulterated wood is not an uncommon practice-Stradivari himself did not rely solely on the properties of maple and ebony, but incorporated borax, zinc, copper, and alum (Su et al 2021). Su et al (2021) have already posited that engineered wood can reintroduce the cellulose rearrangement and hemicellulose fragmentation created by famed Cremonese violin makers of the 1700s. Modern analytical techniques have allowed scientists to identify the properties of prized musical instruments-can these properties be replicated via FGW?…”