Hammers in pianos are extremely durable. They do, however, deteriorate over time. At some point they may need replacing. When this is needed, it is good to select a technician who knows how to do this procedure well.
First it is good to learn a little bit about piano hammers themselves. When hammer heads are manufactured, thick, stiff felt is stretched around a wooden core, or molding, at great tension. The striking surface is smooth and round and more or less egg-shaped. The tension of the felt provides a bounce to the hammers so that when they strike the strings the deflection that they cause to the strings results in vibration or tone.
What causes the piano hammer to wear? The steel of the treble strings and the copper windings of the bass strings gradually cut into the felt. This breaks the felt fibers resulting in a layer of felt on the outside of the hammers which is pulpy or dead. This piano’s tone is altered as this dead layer increases and eventually the hammers don’t produce a clean blow at all, but instead strike the strings with a flattened and grooved surface which produces an unsatisfactorily harsh sound.
Having new hammers installed is an improvement which adds value to the instrument in that the tone of the piano will be vastly improved upon. The piano’s voice won’t be masked by worn out hammers. You might have noticed that some pianos sound shrill while others sound too mellow. The trick is to find a hammer that ideally is suited for your particular instrument that will bring out the best quality of tone possible. The goal is to find a tone that is not too shrill or harsh nor too mellow. A deep tone in the bass and good dynamics in the all areas of the piano is a must. The pianist should be able to play forte or pianissimo and the hammers should handle these dynamics.
This is not to say that once the hammers are installed that this is all to it. The price of installation must also reflect the time the technician must spend in voicing the piano so that the new hammers are sounding their best. This involves usually pricking the felt with needles to loosen the deeper fibers so that the piano can have an open, resonating tone. Sometimes the tone is too harsh, and the area around the striking point of the hammer has to be worked on by these needless. Sometimes the hammer needs more ‘punch’ when it hits the string so special areas of the hammer farther away from the striking point need to get attention.
The final result will be well worth the investment. Speak to your trusted piano technician and ask him about the condition of the hammers.