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9. The fourth string
As mentioned earlier, in the eighteenth and nineteenth centuries the violin G string — i.e. Galeazzi’s cordone — was always overspun. In the eighteenth century, and much of the next century, it had a gut-core (or a silk-core, as we learn from Heron-Allen, in the late nineteenth century), round which was closely wrapped with a round metal wire, silver generally, but also copper or silver-plated copper. On this subject Galeazzi writes: "L'argento, che comunemente si adopera a questo uso è rame inargentato, e deve esser sottilissimo. Si adopera con egual successo il rame semplice, ed anche 1'acciajo: ho fatto a bella posta filare dell’argento fino, ma non vi ho conosciuta differenza dall'argento falso comune, se non che ei non diventa rosso, ma resta sempre bianco, rilucente, come fosse sempre nuovo" (The silver normally used for this purpose is silver-plated copper, and must be very thin. One can equally successfully use copper and even iron. I purposely wound some thin pure silver, but saw no difference from the use of common false silver, except that it does not become red but stays white and shiny, as if always new) (100). It is worth noting that the silver (which had a thickness of just a few microns) was deposited on the copper by simple chemical shift; in the late eighteenth century what is properly termed the galvanic method had not yet been invented and was only to become established towards the middle of the following century (101). According to Spohr, "Die Saiten mit achtem Silberdrath sind den andern vorzuziehen, weil sie einen hellern Klang haben, nicht wie jene, Grünspan ansetzen und nicht durch langen Gebrauch roth und un-scheinbar werden" (The strings wrapped in silver wire are to be preferred to the others, because they give a cleaner sound, and unlike the coppered strings do not attract the mineral green [copper carbonate], do not become red and do not wear out with prolonged use) (102). George Hart provides the following description of the overspun strings of his period: "There are those of silver wire, which are very durable, and have a soft quality of sound very suitable to old instruments, and are therefore much used by artists; there are those of copper plated with silver, and also of copper without plating, which have a powerful sound; and lastly, there are those which are made with mixed wire, an arrangement which prevents in a measure the tendency to rise in pitch" (103).
As the wound strings were made up of heterogeneous materials such as metal and gut, the expression "equivalent solid gut" is used to refer to the diameter of a theoretical gut string of the same weight as the overspun string per unit length. The same tuning and vibrating length will therefore correspond to the same working tension. Care is needed, however, because with equivalent gut the quantities of metal and gut can be distributed according to innumerable possible ratios. For the total weight of the string (i.e. its equivalent solid gut) to remain unvaried, an increase in one element must naturally correspond to a decrease in the other. The more gut prevails over metal, the more the resulting sound will be opaque and lacking in brilliance; and vice versa.
What, then, was the just ratio between metal and gut for achieving a proper balance in the timbre and dynamics of fourth strings? According to Galeazzi, "per fare un cordone di violino, si adoprerà una seconda non molto grossa" (to make a violin fourth string, one needs a not very large second string) (104). Interestingly, this late eighteenth-century recommendation was still applied in the second half of the next century. Maugin and Maigne, for example, write that "la quatrième [...] est un peu plus fine que la seconde" (the fourth [...] is slightly thinner than the second) (105). What, in practical terms, does “a not very large second string” mean?
According to our interpretation, it could mean a string that is still made with the number of guts needed for an ‘A’, but which has a diameter belonging to the lower range of the obtainable calibers.
From the experimental point of view, this should correspond to ca. 0.80-0.82 mm, as is also borne out in the Paganini finds and in the routine manufacturing of today’s strings.
Plessiard (106) seems to be the first author to depart from the custom of using a not very big second string, recommending an ‘E’ string as a core, to be then wrapped with silver-plated copper.
Regarding the diameter of the metal wire to be used, until the late nineteenth-century nothing is known; Galeazzi, however, writes that ‘deve essere sottilissimo...’ (it must be very thin). (107)
The hypothesis of the use of a slightly thin second string surely also applies to Sphor (and probably also Foderà) , given that he expressly suggests that the reader should stretch the core on the violin for a few days, tuning it to ‘C’ (second position of the second string), so that it is well-stretched before it is wrapped. In pratice, this means three semitones of tension more than usual, if the string has a section suited to ‘A’; whereas the operation would be completely pointless if the string were instead just a thinner ‘E’.
On his string-gauge Sphor indicated an external dimater of 1.0 mm. If for example, we accept a core of 0.82 mm (in order to obtain an external diameter of 1.0 mm), what is needed is a metal wire that has a diameter of just 0.09 mm after wrapping (hence after subjection to a certain stretching); in other words, with an initial caliber of at least 0.12-0.13 mm.
By means of a special formula, one can thus derive the diameter in equivalent gut: 1.70 and 1.85 mm respectively, if the wire is made of silver-plated copper or pure silver. (114)
Since this gives a fourth string with a somewhat large diameter, it could be a plausible explanation for the name of cordone given to it by Galeazzi.
Making overspun strings requires a special machine. Galeazzi remarks: "è noto ad ogniuno qual pesante, e lorda macchina si soglia a tale effetto comunemente adoperare" (Everyone is familiar with the heavy and filthy machine customarily used for this purpose) (108). That illustrated in figure 2 remained in use at least until the end of the nineteenth century (109). However, we have observed experimentally that this type of machine is unable to impart a strong tension to the gut core and to the metal wire at the manufacturing stage: since it rotates the string from one end only, rotation is not uniform along the string- whole length (the opposite end tends to turn at a slower speed). Today, on the other hand, the rotation of the two ends is synchronized, ensuring the closest possible adherence of the wire to the gut core, as a greater tension is imposed on both.
According to Spohr the gut core should be first stretched on the violin up to C and then left there for a day before overwrapping. Galeazzi suggests "appiccarla da un capo ad un chiodo, e poi sospendervi sotto un peso immobile" ("attaching one end [of the string] to a nail and suspending a dead weight") (110). By such preliminary operations the gut discharged much of its "non permanent" longitudinal displacement, which in turn ensured that the metal wire would closely adhere to the gut- core for a long duration under tension. Despite this important precaution, overwrapped strings probably suffered frequently from the metal wire vibrating against the gut core, particularly on days of scant atmospheric humidity. The only remedy, before the practice (introduced by the mid twentieth century) of infiltrating a film of silk or rayon between the gut and the metal wire, was that of sufficiently moistening the overwrapped strings with olive oil so that the gut would swell slightly and regain a close adherence to the wire (111). This operation, which we have tested, if well made, not only creates a reasonable barrier to the absorbtion of atmospheric humidity, but also improves the string's sonority.
In the second half of the nineteenth century further improvements were made to the methods of overwrapping strings: such as that, of using together two different metals to ensure a greater stability of the string under particular climatic conditions (112). Neither Hart nor Heron-Allen mentions smoothed over-wrapped strings, introduced only at the beginning of the twentieth century and widely used today (113).
Figure 2. The machine for making overspun strings. Encyclopédie, ou Dictionnaire raissonné des sciences, des arts et des metier [...], Briasson et al., Paris 1751-80.
Towards the late nineteenth century the implications of the information given by Galeazzi seem to have been forgotten. Hart, for example, indicates the tension also of the fourth string, from which we can easily derive the equivalent gut corresponding to the different tensions of the strings he recommends. The tensions of the four strings show a curve that is homogeneously graded. Furthermore, starting from this epoch, it became common practice to employ a violin E string as core, instead of the traditional second string.