THE MAGIC TOUCH

New research has revealed how Stradivari, Amati and Guarneri ‘del Gesù’ all used tonewood that had been heavily treated with chemicals prior to carving. Wenjie Cai and Hwan-Ching Tai explain the study’s findings, and suggest it could indicate that the Cremonese makers were influenced by the contemporary alchemical beliefs

Taking a spruce sample from a Cremonese violin for chemical testing

DAVID HUME

For centuries, luthiers have speculated that the master Cremonese makers may have subjected the spruce and maple they worked with to some kind of modification before using it to make an instrument. The most common belief is that it was simply dried in the air for 5 to 20 years, but many other scenarios have been proposed, including: treatment with acid or alkali; baking; freezing; boiling; chemical baths; and floating the wood in rivers, ponds, lagoons or even oceans. These speculations arose partly because makers needed to account for the thinness of soundboards used by Stradivari and Guarneri ‘del Gesù’, which can average around 2.4mm in the centre, as opposed to 2.9–3.5mm in modern instruments There were some who asserted that modern soundboards could be made as thin, while others were concerned about unbalanced tone and long-term risk of cracking. These debates have inspired scientists to analyse Cremonese wood shavings, collected during repairs, to look for unusual traits.

In 1984 researcher Joseph Nagyvary examined shavings from the top of an Andrea Guarneri cello, and reported finding a concentration of aluminium that reached 700ppm (parts per million), compared with less than 10ppm in natural spruce. In 2013 we began a research project in collaboration with Nagyvary, Brigitte Brandmair, the Chimei Museum and restorers around the world, to investigate the material properties of Cremonese soundboards. We used a wide range of spectroscopic, microscopic and chemical techniques, and found similar types of spruce in Cremonese soundboards as in modern instruments – but the Cremonese spruces exhibited unnatural elemental compositions and oxidation patterns that suggested artificial manipulation. This article will examine the findings of this study in depth, and also explore the possibility that the early Cremonese luthiers were influenced in their search for the optimum tonewood treatment by the alchemical researches of the city’s apothecaries.

In our study, we investigated wood samples from six Cremonese spruces (figure 1) and six maples. All the samples were taken at depths of greater than 0.3mm from the interior side, away from surface contamination. Using inductively coupled plasma mass spectrometry (ICP-MS), we determined the extraneous elements added by Cremonese makers, compared against background references, including old building materials and cheaply made 18th-century violins from Europe.

We found no extra aluminium in Nicolò Amati instruments, and sparing amounts in those of Stradivari (less than 50ppm), but high levels in instruments by ‘del Gesù’ (1,300ppm in spruce and 2,900ppm in maple). This could not be attributed to mineral preservatives pre-applied by wood suppliers, nor random contaminations during later centuries. The soluble aluminium salt in Guarneri’s family recipe was probably alum sold by local apothecaries – KAl(SO 4) 2, NH 4 Al(SO 4) 2, or Al 2 (SO 4) 3. For comparison, immersing a small maple flake in a one per cent solution of KAl(SO 4) 2 for three days raised aluminium levels by 660ppm.

FIGURE 1 Very small samples of spruce from the Cremonese instruments were needed for the chemical examination

PHOTOS AND DIAGRAM HWAN-CHING TAI

The Amati recipe contained fungicides like borax and sulphates of iron, copper and zinc. Their low concentrations (tens of ppm) suggest surface treatments. In addition to inheriting the Amati recipe, it seems Stradivari and Guarneri conducted more audacious experiments that raised aluminium, sodium, chlorine, potassium and calcium levels by thousands of ppm. One of the purposes may have been wood stabilisation and stiffening. Guarneri applied alum to crosslink wood fibres, while Stradivari applied salt seasoning, causing Na and Cl to rise far above sweat contamination levels, altering the activity of water in the wood, as well as its distribution. Another trick was alkaline treatment to remove nutrients and soluble substances, and partially fragment hemicellulose. Guarneri used lime: Ca(OH) 2. Stradivari used potash: K 2 CO or KOH. This may have served to lower moisture absorption, in order to reduce internal damping and improve dimensional stability.

THE PURPOSE OF WOOD TREATMENT

We were surprised to find that luthier Rémy Gug had preempted our findings more than 30 years ago, in two articles in The Strad (‘Salts of Wisdom’, July 1987, and ‘Salted Soundboards & Sweet Sounds’, January 1991). In his historical analysis of using alum, vitriols (metal sulphates) and table salt to treat Baroque tonewoods, his findings showed remarkable agreement with our own. His foresight was inspired by Nagyvary’s report of elevated aluminium and iron levels in the Andrea Guarneri cello, and Karl Schnur’s 1985 analysis of an old violin bridge which contained elevated levels of copper, sulphur, sodium, chlorine, potassium and aluminium. Interestingly, ancient Chinese luthiers also advocated alkaline treatment for artificial ageing and acoustic tuning. They would immerse tonewood in a lime pool for one or two months, then wash out the calcium carbonate precipitates for up to four months in a running creek –a risky procedure by any means.

Amati’s wood preservation strategy apparently worked well. So why would Stradivari and Guarneri risk damaging the wood with much more aggressive chemical experiments? Some modern experiments, using nitric acid and potassium silicate to ‘improve’ the tonewood, have been disastrous when overdone. In our opinion, Stradivari and Guarneri took such risks to achieve acoustic tuning, not merely for wood preservation.

In Stradivari’s spruce and maple specimens, there were striking correlations between aggressive chemical treatments (sodium, chlorine and potassium) and the rearrangement of cellulose. The bundling of cellulose in the spruce of a 1720 Stradivari cello is illustrated in figure 2. This probably altered the speed of sound along different directions of the wood. Importantly, this bundling phenomenon was not observed in an older Amati spruce.

Cremonese wood treatments may have been rather complex and cannot yet be reverse-engineered. We did not find direct evidence of spruce and maple being floated in rivers or oceans, nor being subjected to baking, boiling or sunlight treatment. But nor could we not rule out these possibilities. Much research remains to be done regarding the chemistry of wood ageing, especially on how chemical processing may affect subsequent ageing.

ALCHEMY AROUND CREMONA

So far, scientists have found more than two dozen ingredients in Cremonese varnishes, and at least eight mineral additives in Cremonese woods. Such chemical complexities greatly exceed the expectations of violin makers and scholars. It is very likely that Cremonese makers had consulted experts with alchemical knowledge, but who might they be?

The word ‘alchemy’ of medieval Europe comes from the Arab al-kimiya (the prefix ‘al’ is a definite article), which may have originated from khemia (black earth) in the Coptic language or kim-iya (golden juice) in southern Chinese dialect. Gerard of Cremona (1114–87) translated the first practical chemistry manual into Latin: Liber de aluminibus et salibus (LAS, ‘The Book of Alums and Salts’). All the mineral additives found in Cremonese woods had been described in LAS, and were easily obtainable from local apothecaries. There was also a Hebrew copy of LAS circulating in northern Italy in the 16th century, which contained marginalia about a reader’s discussions with Giovanni Battista Nazari, an alchemist who published Della tramutatione metallica sogni tre in Brescia in 1572.

FIGURE 2 Cellulose rearrangement in Stradivari’s spruce

Medieval alchemy had three levels of meaning. In its narrow sense, ‘transmutation alchemy’ was the futile pursuit of turning base metals into gold. In a broader sense, ‘practical alchemy’ was the technology for producing metals, medicines, perfumes, pigments and suchlike. Then there was ‘spiritual alchemy’, a system of philosophy that sought to decode the mystery of living and non-living things, intertwined with astrology, occultism and magic.

Alum, salt and potash were all employed in the practical alchemy of gut string making. In 1663, string makers of Padua used high-purity potash (K 2 CO 3 obtained by heating ‘winestones’, potassium bitartrate) for cleansing, table salt for preserving, and alum for stiffening. So Stradivari probably knew about these chemicals for the violin business. Moreover, Stradivari’s young adult life was closely associated with two senior architects: Alessandro Capra (also an engineer) and Francesco Pescaroli (also a woodcarver), who may have possessed practical knowledge about wood coating and wood preservation.

The first chemistry professorship in Italy (Ad lecturam Chymiæ) was established at the University of Mantua by the Gonzaga family in 1625. The curriculum followed the chemical medicine of Paracelsus (1493–1541), the father of modern toxicology, who was more interested in manufacturing medicines than creating gold. The Gonzagas even asked Claudio Monteverdi (1567–1643), a former employee, to help acquire chemical reagents and laboratory equipment.

Monteverdi grew up in Cremona as the son of an apothecary (druggist) and continued to practise alchemy throughout his career. His friend Paolo Piazza even called him ‘gran professor della chimica’. In Monteverdi’s time, the symbolism behind alchemy was the search for perfection and the purification of the soul. Although there was no historical record of interactions between Monteverdi (a viol player) and Amati, it would not be surprising if they had discussed alchemical issues in music.

CREMONA’S APOTHECARIES

In 2007 the city of Cremona published a book, Aromatari, Speziali e... Fondegheri, about the early modern history of its apothecaries. From 1400 to 1800 they were called speziali (‘spice sellers’). Around 1500, Brescia and Cremona ranked as the ninth and tenth most populous cities in Italy respectively. Both were devastated by the plague of 1630 and never fully recovered (Table 1). The number of registered speziali in Cremona also dropped accordingly: in 1530 there were around 40 per 1,000 citizens), whereas by 1645 there were 18, and by 1710 just 15.

However, the average over those two centuries gives one speziali per 1,300 Cremonese citizens – comparable to Florence in 1561 and Venice in the early 1600s, two cities well known for flourishing apothecary businesses. The speziali was not only a place to buy perfumes, drugs, sweets and wall paints, but also a community hub for socialising. The owner was usually a druggist/alchemist who knew how to manufacture chemical products for sale. Some physicians and barber–surgeons also served their clients inside apothecaries. In this context, we may understand why Monteverdi’s father was described as a druggist, physician and surgeon.

Unfortunately, we did not find the name Monteverdi in the 1586 survey of speziali in Cremona, a document provided by José María Lozano (figure 3). We do not know if the Monteverdi family operated an independent business. During the 16th century, Cremona was a cultural centre with many painters, sculptors and architects. Its famous painter families included Campi, Anguissola and Presenti. There must have been speziali that sold artists’ materials of high quality, including pigments, oils and varnish resins. It should not have been difficult for violin makers to find knowledgeable alchemists for consultation.

INDUSTRIAL BRESCIA

Although only 30 miles apart, Brescia was ruled by Venice from 1426 to 1797, while Cremona was ruled by Spain (1510–1707) and then Austria (1707–97). Brescia was a more industrial town than Cremona, being a centre for metallurgy and paper making for Venice. We wonder if Brescian luthiers could have engaged in wood treatments by learning from the city’s industrial alchemy.

For example, Renaissance paper makers used lime to stop the fermentation of hemp rags and alum (with gelatine) to size the paper, which were chemicals found in Guarneri’s wood.

There are anecdotes that Cremonese luthiers purchased their spruce in Brescia – from the Bachi family in the 16th century (according to Francisco Bontempi) or from the Banchetti family in the 18th century (according to Paolo Stradivari). Alpine spruce could have been transported to Brescia via the waterways feeding Lake Garda or Lake Iseo. Balkan curly maples, on the other hand, were likely transported by sea to Venice first. Brescia under Venetian rule probably had easy access to Balkan maple. We do not know if Cremonese luthiers purchased their maples from Brescia.

Before the invention of the violin, Bartolomeo Antegnati founded an organ making dynasty in Brescia, which built hundreds of organs as well as virginals and spinets. Clustered around Antegnati’s house were the lutherie shops of Zanetto Micheli, Girolamo Virchi, Gasparo da Salò and G.P. Maggini. His great-grandson, the famous Costanzo Antegnati, taught Bernadino Virchi (nephew of Girolamo) to be an organ builder, and chose the 20-year-old Maggini to be a witness for his testament in 1600. Before the 1630 plague, the Brescian instrument makers formed a close-knit network, while the Amatis worked in relative isolation in Cremona.

TABLE 1 Historical populations in selected Italian cities (thousands). Bubonic plague devastated all of Italy in 1347–48 and the northern cities in 1629–31.

FIGURE 3A 1586 survey of speziali in Cremona

Producing and servicing organs for seven generations, the Antegnatis probably operated a lumber yard and a metal workshop, and accumulated knowledge on the long-term preservation of wood and metal pipes. They used spruce for virginal soundboards (1554, Santa Giulia Museum) and probably also for organ pipes (as in Callido’s Venetian organs). It is plausible that Brescian violin makers had acquired seasoned tonewood from the Antegnati lumber yard or its suppliers. It would be interesting to analyse wood samples from Brescian instruments and Antegnati organs to look for signs of chemical processing.

ALCHEMICAL CONCEPTS OF MUSICAL INSTRUMENTS

In Paracelsian alchemy, stringed instruments were associated with the element of salt. This was expressed in ‘The Alchemical Room’, an illustration from 1595 (figure 4). The oratory on the left represented mercury (spirit), the laboratory on the right represented sulphur (soul) and the musical table in the centre represented salt (body). On the musical table lay a violin/lira da braccio, a lute, a cittern, a harp and a bell. Alchemists considered the vibration of music as a form of transmutation, a defence against sorrow and bad thoughts. This may explain why Bernard Palissy wrote in 1580 that common salt helps the voice of all living things, even all kinds of metals and musical instruments (‘Il aide à la voix de toutes choses animées, voire à toutes espèces de metaux, et instruments de musique’). We do not know if Palissy meant it metaphorically or was actually suggesting salt seasoning of tonewood.

FIGURE 4 ‘The Alchemical Room’, an illustration in German alchemist Heinrich Khunrath’s 1595 treatise Amphitheatrum Sapientiae Aeternae

FIGURE 3 COURTESY J.M. LOZANO

The central theme in Paracelsus’ alchemical processes was spagyria, consisting of separation, purification and reunification. In practical terms, spagyria was applicable to the preparation of herbal medicines; in metaphysical terms, spagyria was a means to purify and elevate the soul. Brandmair and Stefan-Peter Greiner have proposed that the primary resin in Stradivari’s varnish was spruce colophony. If this were true, it could have been inspired by spagyria principles – the resin from spruce trees was collected, purified and added back to spruce wood. Creating potash by burning wood, purifying it through aqueous extraction, and adding it back to the wood could also be considered as spagyria.

Perhaps the greatest influence of alchemy on violin making was the idea that one could follow elaborate alchemical processes and achieve transcendental results. This may explain the chemical complexities that underlie Stradivari’s wood treatment and varnish systems, as recently revealed by scientific analyses. Although we could not find historical records of Cremonese masters tinkering with alchemy, there appeared to be a creative ecosystem around them that could promote the union between art and technology. To rethink violin making in terms of alchemical processes may help us reconstruct their lost working methods. On the other hand, we have a much wider selection of chemicals and technologies suitable for wood treatments compared to Baroque craftsmen. There is little reason to assume that modern makers cannot equal or surpass Stradivari and Guarneri with the help of modern chemistry.

Wenjie Cai is a lecturer of cultural industries at Xiamen University of Technology. Hwan-Ching Tai is an associate professor of chemistry at National Taiwan University. The full study can be downloaded for free at bit.ly/3uOld4c