Under the Microscope: When I was young my mother gave me a violin she had used as a girl, hoping that I would learn to play it, but I regret to say I never took lessons. Prof William Reville writes.
Her violin was a modest instrument, and I used jokingly to refer to it as the Stradivarius. Violins made by the Italian violin maker Antonio Stradivari (1644-1737) have a reputation among musicians for producing sounds of unrivalled beauty.
Nobody knows the secret of Stradivari's unmatched mastery of his craft. The latest theory holds that the perfect sound of Stradivari's violins results from the dense woods used in their construction, which in turn resulted from slower tree growth in the middle of the "Little Ice Age" that prevailed in western Europe at the time. The proposal was published in the journal Dendrochronologia by Lloyd Burckle and H. D. Grissino-Mayer.
Dendrochronology is the science of the dating of past events (principally climate change) through the study of tree rings. Each year a tree adds a layer of wood to its trunk and branches, creating the annual rings we see when viewing a cross-section. Wide rings are produced in good years of growth and narrow rings in poor, dry years.
The violin was first developed in Italy in the early 1500s. The craft of violin-making reached its peak in the 17th and early 18th centuries in the workshops of the Amati, Stradivari and Guarneri families. The most famous was Stradivari, who established his workshop in Cremona in 1644 and worked there until his death. Stradivari made more than 1,100 instruments - violins, guitars, violas and cellos - of which more than 600 survive.
The main parts of the violin are the front, or soundboard, usually made of spruce; the back, usually made of maple; the ribs, which join front and back to form a hollow soundbox; and the fingerboard, pegbox, scroll, bridge and tailpiece. The strings are tied to the tailpiece, rest on the bridge, are suspended over the fingerboard and run to the pegbox, where they are attached to tuning pegs that can be twisted to adjust the pitch of the strings.
Musicians generally agree that the violins made by the 17th- and early-18th-century Italian artisans sound superior to modern instruments. There is considerable debate about why this is the case. The superior sound is generally attributed to a combination of the skills of the craftsmen combined with a "secret" ingredient. Candidates that have been proposed as the secret ingredient include the use of a special varnish, chemical treatment of the wood, drying the wood, seasoning the wood and using very old wood from historic structures.
Each of these candidates has been found wanting. There is no record that early violin-makers dried their wood in ovens. Wood seasoning has been ruled out because of the considerable variability in the lengths of the seasoning periods, even among individual violin makers. Scientific analysis has revealed no "secret" varnish. And the idea that Stradivari used wood from ancient castles or cathedrals has been discounted because dendrochronological analysis has dated the spruce in his violins as having grown in his lifetime.
Maple and spruce are generally used because they have superior mechanical and acoustical properties to other woods. Stradivari probably used the forests of the nearby southern Alps as his source of spruce. Only trees grown at higher elevations in poor soils have the slow growth and dense grain that give a superior tone to violins. Wood that grows quickly is less able to withstand stress and is likely to be less resonant, producing a duller and more muffled sound.
However, high-density wood is found in trees grown at higher elevations around the world. Therefore, the unique quality of Stradivari's violins cannot be explained by generally invoking the properties of high-density wood. If wood is the answer, there must have been something unique about the wood used by Stradivari. And this certainly seems to be the case.
The Little Ice Age prevailed in Europe from 1450 to 1850. But a particularly severe climatic regime gripped Europe during the lifetime of Stradivari. This period, known as the Maunder Minimum, lasted from 1645 to 1715, when the intensity of solar radiation and activity was lessened, causing a sharp dip in temperatures of one or two degrees. The Maunder Minimum is evident in tree-ring records from high-elevation forests in the European Alps.
Burckle and Grissino-Mayer hypothesise that the unique conditions of the Maunder Minimum, with longer winters and cooler summers, produced wood that had slower, more even growth: desirable properties for producing higher-quality soundboxes. During Stradivari's later decades, his "golden period", he used spruce that had grown mostly during the Maunder Minimum. The lower temperatures, combined with elevation and soil conditions, produced spruce with unique and superior sound quality.
This combination of climate and environment has not occurred since Stradivari's golden period, and the authors suggest that this is the explanation for the superlative qualities of the Stradivarius.
William Reville is associate professor of biochemistry and director of microscopy at University College Cork