It is nearly two years since I attended a “Voicing and Tone Production” seminar at Steinway and Sons in New York. The day I walked through the doors at 18-1 Steinway Place, Astoria was a day of new discoveries and ideas in my career. My lecturer was Steinway and Sons Manager for Technical Services and Support, Kent Webb, and his down to earth approach and his guidance made this course rewarding. Kent’s philosophy was to remember that the piano technician is to create a instrument so the pianist can express their musical feelings as well as to create a bond with the instrument. The instrument must also perform as it is designed and performing fancy work without checking the basics….
I had been introduced to the art of hammer hardening before my visit to New York, however my views on the subject were from the idea of the technique being used to hide problems in the instrument as well as a lack of understanding. My lack of understanding from my part was caused from never thinking about the subject due to most of my experience with hammers were that quality hammers needed softening, and not hardening. I had forgotten that I had witnessed some hammer hardening during the voicing process in manufacture of Kawai, Schimmel and Steinway (Hamburg) instruments. If you have ever played a Young Chang, Alex Steinbach, Samick, Pearl River, Kohler & Campbell, Beale, Ritmuller, Kawai or Yamaha (especially the second-hand imports), Petrof, Schimmel, Grotian-Steinweg, Steinway (Hamburg) and a few other brands, you have played a piano with some type of chemically hardened hammers.
Piano hammers are interesting. To look at them they are just a piece of felt wrapped around a piece of wood. But there is more to hammers and to be honest I am just scratching the surface of the subject. There is a theory that the type of wood used in the hammer affects the sound as well as the weight of the hammer. There have been numerous discussions on this subject, and the jury is still out. The woods used are Hornbeam, Maple, Sapeli, Mahogany, Walnut, Kotibe just to name a few. There are several different felt manufacturers that manufacture the felt and there are different grades of hammer felts as well as a number of different techniques used in the manufacture of hammers. Several well known hammer brands are Abel, Renner, Imadegawa, as well as different felts being used, for example Royal George Felt, Werzen, Weikert, and some American brands, Bacon, Ronsen just to name a few. Some manufacturers manufacture their own hammers, however most purchase hammers from a hammer maker.
The finished hammers sound is affected on how the felt is pressed into the hammer. There are generally two different types of hammers: hot pressed and cold pressed hammers. Hot pressed hammers are described as an amount of heat is used in the manufacture to help press the felt as well to speed up the glueing process. Cold pressing is the complete opposite with the felt not being heated. Many long debates have occurred from how a hammer should be made. It would be better to describe hammers as either voice down or voice up. Voice down hammers are manufactured with tension and compression and these require the traditional method of needling in different areas to achieve the required sound. The voice up hammers require the judicial use of chemical hardeners to harden the felt to achieve the sound. There is merit and disagreement with both processes. Hammer manufacturers do not give a lot of information on their own processes but the sheet of felt is glued and pressed around a tapered piece of wood with pressure to create tension and compression. The amount of pressure differs with each manufacturer as well as the type of felt used. The wood and felt is then sliced to become individual hammers.
The piano manufacturers decide what type of hammer they use in the production and use different voicing processes i.e voicing down or upto achieve their final sound. The piano rebuilding industry uses all different styles of hammers and will customise rebuilds with different types of hammers to achieve the customers desires.
Why should hammer hardeners be used?
There are different uses of hammer hardeners. Some hammers start being pressed a little too soft and they require the use of hardeners to bring the level of tone to the required standard. The Steinway and Sons pianos from New York are an example of this. The hammers are made in the factory using their chosen style of hammer felt. The hammers are pressed without the use of high heat or steam, as Steinway believe this changes the properties of the felt. There is also tradition involved in the use of the same hammer making equipment. The tradition of applying hammer hardeners to build up the tone also has its benefits in the extreme climatic conditions of North America. The voicing techniques used by Steinway are generally misunderstood by technicians who are used to voicing the harder pressed hammers. Some manufacturers use hardeners in the high treble or low bass to bring up the sound and other manufacturers correct hammers that are too soft by applying hardener in different areas of the hammer. Some of the areas can be below the staple line, shoulders or striking point.
Before I discuss the hammer hardening process, I must quickly describe the voicing of hammers that require softening to achieve the correct sound. A hammer is best described as an resilient mass of felt that hits the string to create the sound. A hammer has to be resilient enough to “bounce” (think rock and ball) off the string as well have a hard striking point so that different qualities of sound as well as volume can be produced. These hammer heads are generally too hard and produce a reasonable sound when played softly yet do not increase in volume when the key is played harder. The hammers are extensively needled to create the resilience required. Each manufacturer has slightly different techniques in this what they call the first voicing, and this is the most important task when fitting hammers. Unfortunately, unless you do not see this first voicing in the factories or follow their recommendations, many technicians do not understand the importance of this first voicing (pre-voicing) and do not spend enough time on this technique when replacing hammers. Some technicians also believe that needling destroys the felt and will avoid this technique. After a number of hours in this pre-voicing, then shaping (filing)of the hammers, playing-in machines, and the final voicing, the piano is ready to leave the factory.
The softer style of hammer is approached in a completely different manner. The hammers resilient but are too soft, yet produce a nice sound but do not increase in volume when played harder. Needling will not do anything to these hammers. The voicer decides whether the hammer needs more brightness (attack) or volume (body) and the hammer hardeners are used to create these changes. Different types of hardeners have been used over the years from animal hide glue, shellac, lacquers and plastics. There are a few different types of modern hardeners and they all have their uses as well as technicians having their own preferences.
I had my own opinion of hammer hardeners due to the customs of working on hard hammers as well as not understanding the systems used. I have tried using hardeners in the past but I did not like the results. A text book can only provide information but not experience. I came away from New York with a respect and an understanding of their voicing system. There are also uses for the hammer hardener techniques with hammers that have absorbed too much humidity in our climate, as well as customising hammers to achieve a desired sound.
I can also offer clients the choices of different replacement hammer heads. Instead of using hard hammers and needling, I can offer custom soft hammers and use hardeners to build the tone and to offer piano owners alternate parts and techniques.