All of the above (or below in this case). I have had the opportunity to observe and track various hammers over time including in an institutional setting where they were put through the test. The theory is not so difficult. Hammers change and wear due to the stability of the fibers themselves. The hammer is a less than perfect spring. In the process of the elastic collision with the string the hammer flexes but doesn't return exactly to its original form (a sort of hysteresis). The degree to which it doesn't return to its original form is a function of several different factors. First, greater tension in the outer layers provides a more elastic quality to that part of the hammer, a more perfect spring, as it were. Greater interlocking of the felt and healthy fiber provides greater resilience to fiber reorientation as well. Lighter hammers mean less force during the collision between hammers and strings. More flexibility in the strings also accounts for something, possibly differentiating some between treble and bass development.
Hammers that are cold pressed have more tension. Hammers that are simply pressed to a certain density at the expense of tension (and all heat pressing both in the pre and post pressing process will reduce tension) means that the hammer has less resislience, forms a less perfect spring, compacts more readily rather than springs back. Hammer that are pressed (as opposed to stretched) to achieve the requisite density, while they may well sound ok out of the box, tend to develop poorly, become harder and less resilient faster and won't wear as well. In addition, they will invariably require more needling which further disturbs the interlocking and intergrity of the felt, reduces tension and thus allows for greater movement of the fibers in the process of collision with the string. In combination with that notion is the fact that only the highest quality felt that is well interlocked and with healthy fiber can be adequately stretched to achieve a density that will deliver enough power.
Needling and lacquering both reduce the health and resilience of the felt and will therefore shorten the life and reduce the stability of the voicing and therefore the life expectency of the hammer. In the case of hammers, less is more. Ironically, the more the felt needs to be needled, the more often it will need to be needled. Every phase of needling will reduce the integrity of the felt and allow for more shifting of the fiber during impact with the string. That creates less stable voicing, faster changing of hammer shape (crown crushing), more frequent filing requirements, reduction of the tension existing in the outer layers of felt and a shorter hammer life.
Lacquer has a variety of problems. First, it tends to be required on felt which is already inadequate, lacking structural integrity and some minimum level of density or tension and thereby allowing for greater movement of the fiber. Second, the lacquer stiffens the fiber and reduces whatever elasticity it may have. Too much lacquer can make the fiber brittle, it won't hold up to any type of collision without movement or damage to the fiber itself. Third, laquer continues to harden over time and as you go deeper into the hammer where the felt transitions from being under tension to being under compression (this aspect of the hammer changes as you go deeper into it) the lacquer tends to bind everything. Lacquered hammers generally do not develop well over time and filing reveals the weakness in the concept. The more plasticized layers that are uncovered as you file become something other than felt as you delve deeper into the hammer.
The current hammer making trends generally, in my opininion, are largely misguided, based on I don't know what: production schedules, bad habits, some trend whose basis is a mystery to me, acceptance, for some unknown reason, that massive amounts of needling are the norm and to be expected, fear of inadquate power, a wrong headed attempt to minimize factory voicing procedures before the pianos are put out for sale. I'm not really sure. As I mentioned, the use of lacquer as a routine practice comes from a period in which the hammer that was made was wholly inadequate and some remedy needed to be found. The innovative techs in the factory came up with a solution. That became an accepted norm. I might add that it belongs to a single manufacturer. The hammers that you referred to from the earlier part of the century were much more on track, more elastic felt, no heat used in pressing, thinly profiled, not excessively heavy, quality felt. On many of the current instruments where the hammer has changed the scale and soundboards have not, thus the requirements should not have changed. Admittedly, there are cases where heavier soundboards with higher tension scales have been developed and it may be appropriate there to produce a heavier hammer. That the hammer needs to be pressed in such a manner to reduce resilience I think is a mistake even if the energy input requirement in those systems is greater. That sacrifice, in my view, is not necessary.
It is certainly no secret that I am disappointed in the state of hammer making generally. New products are constantly being introduced yet they are generally just more of the same. Apropos of this disussion there are any number of hammers being produced that sound relatively ok out of the box. How they sound after even a modest amount of playing is another story. Here my experience following may of these Golden Geese has proven disappointing. The eggs they are laying are certainly not gold.
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David Love RPT
www.davidlovepianos.com davidlovepianos@comcast.net 415 407 8320
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Original Message:
Sent: 07-18-2013 18:54
From: Allen Wright
Subject: Hammer suggestion
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Allen Wright, RPT
London, United Kingdom
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David,
Is this based theory, on your personal observations and experience (ie. anecdotal), or maybe (even better) some sort of "controlled" longterm observations-perhaps at an institution?
Original Message:
Sent: 07-17-2013 07:24
From: David Love
Subject: Hammer suggestion
In terms of longevity, the hammers that will last the longest will be lighter, rather than heavier, have more, rather than less, internal tension, will have had less needling (see my previous point re tension), not be lacquered.
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
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