STRINGING IV: Wire type identificationEntire Contents Copyright © 2022 CBH
|The three main types of wire can be seen in the tenor and bass of this Virginal
(Plain Soft Iron, Yellow Brass and Red Brass)
Wire type identification…
There are several types of wire commonly used for harpsichord strings. Depending on its tradition, any particular instrument will typically use one, two or three different stringing materials, with the heavier alloys being used towards the bass. The wire also varies in diameter, and according to its design, an instrument might have a range of about six to fifteen diameters.
Some instruments, particularly twentieth-century style harpsichords with a 16´ register, or some clavichords, may use overspun (covered) strings rather than plain wire. Like the bass strings on a piano, these help increase the mass of the wire for lower pitches without increasing the stiffness. Such strings must be specially made to order.
For replacement of broken plain strings, it’s always good policy to attempt to match the original material and diameter. Some instruments may have string diameters marked in pencil on the nut or wrestplank veneer, or behind the nameboard for German- or Italian-style harpsichords. Many makers provide a stringing list or schedule with the delivery of a new instrument, or will do so on request. Some makers go so far as to deliver a replacement wire set with a coil of each size, complete with a nicely made loop.
When undertaking a complete restring of an older harpsichord, it may be desirable to substitute a different material for tonal improvement. This page details the most common materials used for strings on early keyboard instruments today. Please refer to our Wire Size Chart for available diameters of each material.
The tensile strength of steel is necessary to withstand the high string tension of the modern piano, and this “music wire” is also drawn by Röslau GmbH in smaller diameters for use from the tenor up in the typical long scaling of twentieth century-style revival harpsichords. If the speaking length of c'' is greater than 35cm on an A440 instrument—or 37cm at A415—steel is the only possible stringing material to use: The historic-style softer iron wires [discussed below] will break. Steel has a highly polished silver appearance that is resistant to corrosion, and short lengths are noticeably very stiff and springy compared to softer iron.
Tinned Soft Iron
Low Tensile Steel (LTS) or Soft Iron contains a lower percentage of carbon, typically less than 0.2%. The wire is wiped with molten tin to leave a surface coating that delays corrosion, but this can give an inconsistent finish from batch to batch, sometimes with a distinct yellow to orange cast to the natural silver base color. First popularized by David Way in the mid-1970s, this wire has typically been used by makers working in historic style, including the range of Hubbard and Zuckermann kits.
Plain Soft Iron
Our unplated US-made iron wire has traces of Carbon (0.18%) and Manganese (0.69%), and has quite a dull grey appearance.
The Soft Iron wire drawn by Malcolm Rose in England is also unplated, and has been used for a long time for tonal reasons by many of the higher quality makers. It is made in several grades: The “A” is used for harpsichords, “B” for early pianos, “C” is harder drawn for pianos up to 1830, and “D” for pianos later than that. The wire has a smooth, polished silver appearance that is difficult to visually distinguish from Steel when on an instrument, although it is inclined to rust quickly in dusty, humid or corrosive surroundings. It is noticeably softer and easier to bend than Steel.
This iron wire is so-named because of its phosphorus content with next to no carbon, based on chemical analysis of surviving strings on original instruments. P-wire has been thoroughly researched, developed and tested over the past decade by Stephen Birkett at Canada’s University of Waterloo, and is now being produced in commercial quantities. It is drawn in the proportional Nuremburg sizes and later batches have been reported to have the added advantage of natural corrosion resistance.
Phosphor Bronze is an alloy usually containing about 90% Copper, 9% Tin and a small amount of Phosphorus. It was typically used for the bass of instruments prior to the mid-1980s, crossing over to Steel with or without an intermediate Yellow Brass section. As it will withstand a higher tension than Yellow Brass, some makers used it as a stronger substitute in clavichords and Italian harpsichords, although the tone produced by this wire tends to be somewhat harsh and fizzy. The use of Phosphor Bronze as a bass stringing material was largely discontinued by 1990 when Red Brass became more readily available. It has a dull coppery appearance and is very stiff. Bronze was traditionally drawn in Imperial Wire Gauge, where the gauge numbers get larger while the diameter decreases: This can create confusion on those revival harpsichords with gauge numbers stamped on the wrestplank.
So named because of its distinctive color due to its high Copper content, Red Brass was pioneered by the US maker Willard Martin in the early 1980s. With its strong fundamental, it soon became regarded as a better tonal choice for the extreme bass than either Phosphor Bronze or Yellow Brass. The wire is typically 90% Copper and 10% Zinc, although 85% and 95% alloys have also been used. With a bright coppery appearance, Red Brass wire is notably soft and easily kinked or bent.
Rose Red Brass
Malcolm Rose also draws brass wire from European alloys. As with his iron wire, it is popularly used by many of the higher quality makers. Compared to the US-drawn Red Brass, the Rose production has a distinctive earthy glow rather than a bright appearance.
An alloy of 70% Copper and 30% Zinc gives the expected bright brass color of this commonly-used wire. Yellow Brass has been used for many years in the bass and tenor regions of instruments, although now the extreme bass of most Northern European instruments is usually strung in Red Brass. The strings most at risk of breakage on these instruments are those in the lower tenor where this wire crosses over to iron. This material will not stand rough handling or kinking without breakage, and the smaller diameters are particularly fragile and must be carefully handled. Some instruments (eg many clavichords, spinets and Italian & German-style harpsichords) are designed to be strung throughout in Yellow Brass. It cannot be used if the speaking length of c'' is greater than 29cm on an A440 instrument—or 30cm at A415.
Rose Yellow Brass
As with the rest of the Rose production, this wire is popularly used by many of the higher quality makers. Again, the European alloys used gives this wire a distinctive earthy appearance compared to the bright US-drawn stock.
Stephen Birkett has drawn small batches of both Red and Yellow Brass in the proportional Nuremburg sizes shared with his P-wire, but the brass is yet to be available in commercial quantities. The wire is extremely soft compared to the other historic brasses available, and has slightly reduced breaking strain.
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