The leather used by piano makers in the late 18th and early 19th centuries for covering hammers is no longer available. Therefore, if it is necessary to replace, an alternative needs to be found that has similar properties to the original. The choice of replacement leather is critical to the tone of the instrument.
It is difficult to be definitive about the exact tone that was intended by the maker. The two main reasons for this are that the original hammer coverings will have changed from playing the instrument and the leather will have aged and become hard, porous and dry. These changes will have affected the quality of the leather and therefore also the tone of the instrument. Given these circumstances it is inevitable that there are differing opinions about tonal character and the original intentions of piano makers. It is possible that our familiarity with the sound of the modern piano clouds our perception of how an early piano should sound.
Informed judgement needs to be taken about the leather that is used for recovering hammers. Hammer leather should have the qualities to enable a wide dynamic range and have sufficient elasticity to be tensioned over the face of the hammer in a controlled way to enable a balanced tone throughout the compass of the instrument. Apart from the quality of the replacement leather, the way in which the leather is applied to the hammer core is vitally important to the sound produced.
An initiative to source leather in 2013
Suitable quality leather is almost impossible to find from current commercial sources and many professional restorers are desperate to find a new source of supply. Therefore, an initiative was undertaken in 2013 to replicate the principal types and qualities of leather that were originally used by piano makers. This was done in liaison with a specialist in the UK leather industry.
This initiative to produce hammer covering leather was intended for all types of early pianos but primarily for English grand and square pianos of the late 18th and early 19th centuries.
The leather that has been identified for replication includes:
- A replacement for the vegetable-tanned sheep leather used for the outer covering of early instruments from the 1760’s to about 1795.
- A replacement of the oil-tanned leather (buff-leather) used for the outer covering of hammers from about 1795 to 1835.
- A replacement of the vegetable-tanned and oil-tanned leather used for under leather.
Similar qualities of these leathers used as a cushion within various parts of the action and keyboard.
Original hammer covering samples were tested in a laboratory to establish generic tanning method and the animal from which the leather was produced. It is not necessarily the case that the same quality of leather can be produced from the same animal skin used originally as both the animal and conditions have changed. It is more important that a type of animal skin used today best replicates the quality of the original leather.
Some vegetable-tanned hair sheep leather has been produced by an English tannery that is suitable for some applications. In 2013, work was undertaken in liaison with the Institute of Creative Leather Technology, Northampton University, UK to establish leather specifications.
Fig. 1 New veg-tanned hair sheep leather that is suitable for some applications.
Fig. 2 A hammer-head from James Ball grand piano of 1800 with the original under leather shown with the new veg-tanned hair sheep leather. The oil-tanned outer leather has been removed.
Postscript August 2019
The production of suitable leather is fraught with difficulties including finding suitable skins for tanning and the consistency in quality of these skins. Understandably, The leather industry is geared towards meeting the requirements of the major market sectors rather than a small niche market for early pianos. Therefore there is a limit to the research and development resources that the industry is able to provide.
It is unfortunate that since this article was written in 2013 it has not been possible to commission suitable leather. The hair sheep leather referred to above was not a dependable source and is no longer available. Leather that has some merit is available occasionally from suppliers and manufacturers but only in small quantities from a one-off batch production.