Stringing early keyboard instruments
This is a very delicate part of the conservation of early keyboards as departing from a not too very wide margin of string tension can lead to a poor sound or to a twisted instrument with possibly irreversible damage to the soundboard, bridge and nut, not to speak of broken strings. Apparently, instrument makers did not calculated the gauges they used in their instruments scientifically, as we can now. They must have used trial and error to come with the right gauges, and passed that experience to their apprentices; and this situation lasted probably until the first quarter of the ninteenth century.
As metallurgy and science in general developed, improvements in the wire making industry resulted in a much stronger iron wire. For example, the addition of manganese allowed the possibility to have a wire that will stand higher loads. While this was welcomed by engineers, it came with a cost to the musical instruments making. In order to have a pleasent sound, strings have to be tightly stretched, but the wooden instruments were not capable to hold such load without twisting. Then the race to have stronger cases in the instruments began, and only by the end of the nineteenth century a balance between the needed tensile strength in the strings and the construction of the cases was reached, mostly by the introduction of the cast iron frame. This is basically the period when the modern piano started. Harpsichords, clavichords and spinets were left behind even before this race began, probably because people favored the fortepiano. The last harpsichords made in England date from the first decade of the nineteenth century.
String calculation charts.
Even today, conservators (sometimes referred to as restorers, techincians, etc.) struggle to find the right strings for an instrument. There are a few causes for this, being one that the original strings are not present anymore and have been replaced with more modern ones, sometimes at the point that modern piano wire was used, ruining the instrument. Another one is the lack of experience. There are different string calculators, but they will give you information about the diameter of a string necessary to obtain a certain pitch, given a density. But the calculator cannot predict if a specific instrument will twist (or re-twist) or not under such load. Also, there were typical stringing guidelines in different periods. For example, square pianos by Beyer or Beck had red brass cores in the wound bass strings. Another frequent problem is when new strings break. Was it due to a miss-calculation of the strings, the wrong alloy, errors in the measurements of the speaking lengths, a poor manufacture of the eyes, too much bending of the wire when fitting the wrest pin, or was a defective wire? Sometimes a new instrument seems fine with the new strings and after a few weeks the bridge is moving, the soundboard sinking, or the whole instrument is twisting. The result is that the strings have to be removed, the damage repaired, probably by taking out the soundboard and/or bridge, and restring it again. If the instrument is in another city or country, the cost of bringing the instrument back to the workshop has to be added. I guess all restorers had at one point one of such failures, and that's when they decided to work only with an informed calculation. Such calculations can be obtained from a few restorers who have a big enough database and experience in stringing, and usually they cost less than one hundred pounds (110 euros, or 120 american dollars).
If you want to have a string calculation, please send us an email to the following address and we will contact you: cesarhernandez1967(at)hotmail.com. We can attend enquiries also in Spanish, Italian, French and Russian.
We can also provide covered strings for square pianos, and whole sets of strings. Also, strings for harpsichords and clavichords.
The minimum order is 20 pounds, which is roughly the cost of three or four plain strings, + postage. Payments can be made through PayPal or bank transfer.