Hammer Covering and Leather

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.

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, a new initiative has been taken to replicate the principal types and qualities of leather that were originally used by piano makers. This is being undertaken in liaison with a specialist in the UK leather industry who has already produced authentic historical leathers for various other disciplines. Samples of bespoke vegetable-tanned and oil-tanned leathers are being produced based on a range of the original leather fragments. The specialist is committed to this initiative and has the resources available to put into commercial production leather that is found to be suitable, if there is a demand to do so.

This initiative to produce hammer covering leather is intended for all types of early pianos but at present it principally covers hammer leather for English grand and square pianos of the late 18th and early 19th centuries.

The leather that has been identified at present 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 have been tested in a laboratory to establish generic tanning method and the animal from which the leather was produced. New leather samples have been made using 18th century tanning processes. 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 produces the quality of the original leather. Further samples of leather are being produced over the next three months.

Leather that shows some merit for recovering hammers will need to be extensively tested before any commercial production could be undertaken. The production of leathers can only be achieved with a collaborative effort between makers and restorers and the leather industry.

The support from makers and restorers to this initiative has been encouraging and I would like to thank those restorers who have provided me with fragments of original leather taken from period instruments, and given feedback on the new samples produced so far. I would welcome from restorers any original pieces of hammer covering leather particularly from Viennese instruments so that a thorough analysis of the original leather can be completed.

Some vegetable-tanned hair sheep leather has been produced by an English tannery that is suitable for some applications. Work is currently being undertaken in liaison with the Institute of Creative Leather Technology, Northampton University, UK to establish leather specifications.

New veg-tanned leather

New veg-tanned hair sheep leather that is suitable for some applications.

A hammer-head from James Ball grand piano of 1800 with the original under leather shown with the new veg-tanned hair sheep leather

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.

An independent trial of using this leather has been undertaken in the United States and a report of its use is given on the website:   http://www.squarepianotech.com/?page_id=9

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 and it is taking longer than expected to produce suitable leather.

I would welcome any comment including that from makers and restorers and from the leather industry.  Please email: graham@earlypiano.co.uk