Pianotech

  • 1.  Lacquer or no?

    Registered Piano Technician
    Posted 06-14-2018 21:10
    In light of the recent conversation about the different voicing methods between lacquered hammers and non-lacquered hammers, I have a question, but thought it would be better to start a new thread. 

    Why do lacquered hammers require lacquer in the first place?

    And, why do some techs claim lacquered hammers are superior to non-lacquered hammers? (Assume that the quality control is the same in each manufacturing process.)

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    Benjamin Sanchez
    Professional Piano Services
    (805)315-8050
    www.professional-piano-services.com
    BenPianoPro@comcast.net
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  • 2.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-14-2018 23:52
    There are many factors that I cannot cover in a simple post. But I will attempt to help your thinking by pointing out that the hammer both excites the string and damps it. The exciting part is variable with velocity, as is the damping. The predominant damping control is the mass of the hammer in proportion to the periodicity of the string. Fast treble strings need hammers way lighter than ones in the middle and bass in order to not damp too much.

    Good hammer felt also behaves like a non-linear spring in that the speed with which it recovers from impact deformation is slower with loud blows than with soft ones. This gives a piano the tone color change with dynamics. In the high treble, this is less important than the middle and bass portions.

    A properly toned set of hammers for the full compass requires very little change in mass and felt spring rate for the first 35 or so notes, after that the rate of weight reduction and increased felt stiffness must change in a more exponential function. Much like the frequency chart curves. Another way to think about hammer weight is to recognize that the hammers start out oversize and the tone-regulator must cut them down to fit the piano.

    It is nearly impossible to make a set of hammers that fits the requirements for exponential rate of stiffness change across the compass that you can simply pull off the shelf and glue on the shanks. This is because in the hammer felt and hammer making process the stiffness can only be made to change in an arithmetic fashion rather than exponential across the compass. One end of a clamped gluing structure cannot have 1,000 times the clamping pressure it has in the middle at only one end and have the other end at the same pressure as the middle.

    My advice is before you use lacquer see if the weight can be reduced on the hammers. This will bring the brilliance up, especially in the top treble. If you can get the tone to such a state that no added brilliance is needed in the first 50 notes or so, adding felt stiffening agents can be employed with less chance of negative impact to the upper notes. Over stiffened hammers loose variable felt stiffness and the tone will lack color change plus the shift pedal often takes on an awful twang because of the crust on the hammers edge.

    I much prefer nitrocellulose lacquer in acetone for stiffening. Nitro lacquer breaks down over time so as the hammer pack down from playing the lacquer will break down some. The acrylic plastic popular with some today will not do that to the same extent. I use about 10 to 1 thinner to lacquer and apply right on the strike point. Don't bother filling the entire hammer except in the top few notes. Let it dry a few hours and if it sounds too bright just re-wet the surface with acetone and wick some lacquer out of the hammer with some paper towels. Be sure to have adequate ventilation and protect the action from spills by protecting things with some newspaper.

    Using tone building tone regulation methods that reduce hammer mass to bring brilliance up and stiffen treble felts as needed have been proven to result in the most wear resistant actions that are very stable both in touch and tone character. Heavy, hard, needle down, hammers wear faster and keep climbing back up with excessive brilliance. Plus heavy, hard hammers slow the touch to such an extent pianists can get injured playing them.

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    Edward McMorrow
    Edmonds WA
    425-299-3431
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  • 3.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-15-2018 11:50

    Voicing hammers

     

    As usual, Ed has a well thought out, inciteful, borne from experience, explanation of how hammers work, and why we (and the manufacturer) use some kind of hardening agent.  At the risk of over expounding on Ed's reply, the hammer must excite the string, remain long enough to squelch the harsh partials, but long enough to get maximum volume of the desired ones, mainly, the fundamental.  Ed's right about hammer mass, as it relates to tonal components: too heavy a hammer, it can't get away from the string fast enough, due to inertial effects.  Too light, and it doesn't have enough mass to excite the string such that there's adequate volume and tonal qualities.  Additionally, the mass of the hammer has a dramatic effect on the touch and feel of the action.  Too heavy a hammer, the action feels heavy and sluggish, with poor repetition.  Conversely, too light an action feels "fly away" and hard to control when playing softly.  The challenge, from the manufacturer's and rebuilders perspective, is to find that "sweet spot" of mass vs felt density/hardness.

     

    Let's move on to the actual felt of the hammer.  Basically, there are 2 types of hammers: "hard" pressed (large amount of felt compressed to make the hammer), and "soft" pressed (smaller amount of felt compressed to make the same size hammer).  Examples of "hard" pressed hammers would be European and Asian hammers.  An example of "soft" pressed hammers is Steinway.  Both have advantages as well as disadvantages.  Why hard pressed vs soft pressed?  In part, it comes down to string tension.  The higher the string tension, the more force needed to excite the strings.  For example, Steinway is considered a "low tension" scale, averaging approx. 195 lbs. per string tension.  Bosendorfer, Yamaha, and other European/Asian pianos average approx. 215 lbs. per string tension.

     

    Hard pressed hammers get the best tone when the tension and compression is released by proper needling; primarily staying away from the crown of the hammer.  Soft pressed hammers, on the other hand, get the best tone when some kind of hardening agent is introduced into the hammer felt, then needling the crown of the hammer to produce the desired tonal qualities.

     

    I remember Tom Kaplan and I teaching a voicing class at a conference where Scott Jones taught a Steinway voicing class just before we taught a Yamaha voicing class.  Scott and I had dinner the night before to compare notes so that our classes could dovetailed with each other.  The next day, I opened the Yamaha class by asking the question: "So, who attended Scott's voicing class?".  Much of the class raised their hands.  "Well", I said, "Those techniques work on Steinway's soft pressed hammers.  The techniques Tom and I will be teaching work on Yamaha, or hard pressed hammers. Not on Steinway hammers".  The lesson here is that we need a tool box of techniques, and the understanding that we need to use the right tactics for the hammers we're working with.

     

    This is a way oversimplified explanation, but I hope it helps this terrific discussion!  By the way, a hearty "Oh ya!" to Ed's comment of hardening with nitrocellulose and acetone.  The acetone flashes quickly, so you can voice and play the piano sooner.  Additionally, as Ed stated, that solution breaks down as the hammer naturally wears and hardens, so, the tone stays quite stable over a long period of time!



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    Brian De Tar, RPT
    Portland OR
    503-201-5482
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  • 4.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-16-2018 11:57
    I'd probably want to clarify a few points made here:

    The difference in mass of hammers mostly relates to damping effects rather than the ability to deliver energy.  A bass sized hammer in the treble will, indeed, damp too many high frequencies, a light hammer in the bass will not damp enough.  

    Actions don't necessarily feel heavy and sluggish with more mass in the hammers, it depends on the action ratio that they are combined with.  A hammer with high mass can feel quite facile if the leverage is a good match.  Similarly a low mass hammer with a high action ratio will not feel fly away.  

    You wrote:  "Basically, there are 2 types of hammers: "hard" pressed (large amount of felt compressed to make the hammer), and "soft" pressed (smaller amount of felt compressed to make the same size hammer). " 

    This is not quite right.  Soft pressed doesn't refer to the amount of felt but rather the pressure applied in the press and/or the amount of heat used in the pressing process.  Hammer makers use varying amount of both heat and pressure.  A hammer pressed without heat can still be made quite hard.  Steinway hammers come out of the press quite soft but they tend to also be quite bulky.  

    Best fit can take into consideration string tension but better if both string tension and soundboard structure are both taken into consideration.  Lighter assemblies generally will be better with lighter and softer hammers, heavier assemblies usually require heavier hammers.  Steinway's low tension scale, btw, is more on the order of 150 - 160 lbs per string (plain wire).  Yamaha string tensions are around 175 lbs, Bechstein and Bosendorfer are higher.  Scales tensions are not always uniform across the scale.  

    I would probably take issue with the notion that nitrocellulose lacquer breaks down over time.  That type of lacquer gets harder over time which is why it's good and durable on furniture.  I do think that the fiber probably breaks down over time since the lacquer makes the once resilient and flexible fiber much less so, in fact quite brittle.  Try this.  Go to the yarn store, buy some wool yarn.  Divide it into two wads.  Squeeze one and let go, the yarn springs back more or less.  Saturate the the other wad with your typical 4:1 solution used by Steinway.  Let it cure.  Squeeze that wad.  You may hear a nice crunching sound and the yarn will not spring back nearly to the same degree as the other one.  An indication of what lacquer does to the resilience of wool fiber.  Basically it destroys it.  


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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 5.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-15-2018 11:04
    Ben,
    I wouldn't make a blanket assessment of lacquered or non-lacquered hammers. Lacquered hammers may be advantages for those technicians who lack experience with lacquering, where non-lacquered hammers provide an "open architecture" for the experienced technicians. Material, quantity, and placement is the key to success with lacquering.
    Roger





  • 6.  RE: Lacquer or no?

    Posted 06-15-2018 11:34
    I was always wondering why dilution is used as a vehicle for penetration of lacquer rather than the more efficient surfactants that lowers surface tension of the lacquer.





  • 7.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-16-2018 02:16
    The main reason lacquers are diluted is not for penetration, it's to reduce the solids content.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 8.  RE: Lacquer or no?

    Registered Piano Technician
    Posted 06-16-2018 12:00
    If you think of hammers as springs that have varying degrees of stiffness, lacquer is added to hammers to increase the stiffness of the spring.  It does that by coating the fibers and essentially increasing the diameter, by making the fiber more rigid and by adding some density to the overall hammer.  In so doing the springs compress less, less energy is absorbed by the hammer and more is delivered to the string (louder).  Also, stiffer springs will remain in contact with the string for a shorter period of time thus damping fewer, especially, high frequency partials for reasons mentioned in another post.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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