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keytop solution

  • 1.  keytop solution

    Posted 12-27-2019 12:34
    Hi!  I'm trying to dissolve keytop material in acetone, and it doesn't seem to be working.  Actually I'm using key fronts, which I assume is the same thing.  (There I go assuming).  The plastic swells up and breaks up and maybe partly dissolves, but after a week there's still a lot of undissolved material.

    So questions:
    -  What are keytops made out of?  I think ABS, which should dissolve in acetone.
    -  Are key fronts the same?
    -  It's possible the acetone is saturated with the plastic and won't take any more?
    - Is this normal or what am I doing wrong?

    Also I tried applying the liquid to some cloth and some cotton swab, and it didn't seem to stiffen things up  noticably.


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    Eric Schell
    ericschellpiano@gmail.com
    Austin TX
    512-363-6236
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  • 2.  RE: keytop solution

    Registered Piano Technician
    Posted 12-27-2019 21:22
    Mr. Schell,
    Last I checked "plastic"key tops are usually made of PMMA (polymethylmethacrylate). One key top will dissolve in 8oz of acetone in about 8 to 12 hours. The same is true of 5 grams of B-72 in 4oz of acetone for a comparable strength solution.

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    Karl Roeder
    Pompano Beach FL
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  • 3.  RE: keytop solution

    Registered Piano Technician
    Posted 12-28-2019 01:51
    Use something else. Either buy ground plastic from Pianotek or stick with lacquer. I'm not a fan of plastic anyway.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 4.  RE: keytop solution

    Registered Piano Technician
    Posted 12-28-2019 12:53
    I've never liked plastic in hammers, either the sound, or having it in the hammers and very hard to remove.

    Shellac, while more temporary, seems more controllable, the sound pleases me a lot more, and the ethyl alcohol carrying it is less toxic than acetone or lacquer thinner. It's temporary, to a greater or lesser degree (unknown why the difference), I theorize, because it is brittle when set up, so heavy playing over a few days tends to fragment it, decreasing the brightness.

    Can anyone tell me? Does keytop in hammers get brighter with heavy playing?

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    Susan Kline
    Philomath, Oregon
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  • 5.  RE: keytop solution

    Registered Piano Technician
    Posted 12-28-2019 16:30
    Susan,
    I understand your concern about plastic in hammers. I wonder if you're drawn to that conclusion because of your perception of plastic striking a steel string. Yes, it is an ugly sound, akin to fingernails on a chalkboard. Keytop material is too hard to be subjected to string contact. It creates a top-heavy waveform which manifests into sizzles and buzzes. If you keep the plastic away from the string, you can provide a firm and stable foundation for overall power delivery with little effect on the upper partials. This provides a more suitable (my opinion) platform when working in the higher partials with a softer hardening agent. As a general rule, I keep acetone/keytop material below the 9 – 3 range.
    Roger   





  • 6.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 02:56
    Yes, what you say makes sense. Many years ago I used a very dilute solution, and very little of it, up at the strike area, on just a few notes softer than the others. It sounded bad, and it kept sounding bad, even after I needled it.

    Have you tried dripping it in from the sides? Might it be all right to provide support up between 11 and 1, if put in from the sides and not allowed to reach the outer layers?

    I doubt I'll try it again, though. If I decide to, I'll probably use lacquer instead of plastic, and keep it in the lower half of the hammer.

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    Susan Kline
    Philomath, Oregon
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  • 7.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 12:07
    Susan,
    Yes, I do apply the keytop/acetone (K/A) from the sides as well as the outer perimeter. I want it to penetrate throughout the felt. I have used K/A are far up as 11 – 1 but with extreme caution and only in the top half octave. Another visualization comes from the importance of balance of power in the upper partials – particularly in the top two or three octaves. Soft hammers fail to deliver these important upper partials which manifests as muted power. The mental picture I believe many of us have is to apply a hardening agent at or near the crown, which, by  rote logic, would solve the problem of weak upper partials. The problem with that generalized mental picture is we have a tendency to apply the hardening solution to a wide breadth of felt. That scenario is difficult to control because the hardening agent may not be of the correct stiffness to reach your target waveform. My visualization protects an area of felt from any stiffening agent between the shoulder and some point leading up to the immediate crown. The upper partials are then addressed by confining the hardening agent to a small area that has immediate contact to the string. That small hardened area (I visualize as a small hard ball) now "floats" (springs) on virgin felt supported by a firm shoulder. To confine the hardening agent (lacquer) to the immediate crown target area, I use lacquer as thick as molasses -- add more for increased upper partials and apply a drop of thinner to the crown to reduce the upper partials.
    Roger
    P.S. This outline is an over simplification because there are many exceptions





  • 8.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 02:30
    Ethanol (alcohol) is easily digested by the body, but so is acetone.  Acetone is actually made by the body and is a common by-product of fat digestion.

    In small amounts both are probably not harmful.

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    Blaine Hebert
    Duarte CA
    626-795-5170
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  • 9.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 03:08
    Blaine, a short wander through the web shows that you are right. It's far less toxic than methanol, for instance.

    I do keep some nail polish remover in the trunk in case I commit an indiscretion with CA, and end up gluing myself to myself as once happened when I was installing a rubber button.

    Of course I don't plan to bathe in acetone anytime soon, but small amounts appear to be more of an eye irritant than a liver threat.

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    Susan Kline
    Philomath, Oregon
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  • 10.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 02:52
    Susan wrote: "Can anyone tell me? Does keytop in hammers get brighter with heavy playing?"

    All plastic solutions will cause greater instability in hammers in terms of maintaining levels of "brightness".  The reason is because all additives cause the fibers of the felt to be less resilient.  By that I mean they reduce the fiber's ability to return to it's original form after the hammer is compressed against the string(s).  Laquers, plastics, even shellac, all make the fiber more brittle. The return of the hammer to its original form is what defines stability.  Anything which compromises that ability  reduces tonal stability and therefore causes the hammer to get brighter over time.  

    That goes not only for instability due to the addition of chemicals which make the fiber more brittle but also in the manufacturing of the hammer which can reduce the resilience of the fiber from excessive heating or from poor quality felt in which the felt fibers easily shift position when compressed (another reason for instability).  While we may welcome a very soft hammer's ability to become more dense through playing over time we certainly don't welcome a hammer which is hard to begin with and lacks resilience and too easily becomes more dense than we desire.

    Needling hammers similarly causes the hammer to be less stable because we disturb the natural structure of the hammer which gives it the best chance to return to its original form after compression.  More needling, more disturbing of the continuity of the structure of the hammer progressively makes the hammer less and less stable.  The more we needle the more we will have to needle.

    Hardening agents produce the double whammy of not only making the fiber more brittle and less resilient but also often require us to needle the hammer to address the hardening agent itself.  

    The most stable tonal outcome is produced by using the best quality hammer both in terms of fiber resiliency and hammer consistency that requires the least amount of manipulation by either hardening agents or needling.  I have found that there will always be some initial settling of the felt in the first many hours of playing but that a well made and uncompromised hammer will then tend to stabilize after that intial settling.  Thus the ideal hammer (in terms of stability) is one that starts just under the desired level and plays in within a reasonable amount of time to the desired level.  




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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 11.  RE: keytop solution

    Registered Piano Technician
    Posted 12-28-2019 11:31
    Eric,
    I'm no chemist, but I believe you're trying to dissolve the wrong plastic in acetone. I'll make a guess your making a hammer hardening solution; a solution I've used for years with excellent results when applied in the correct location. The plastic that dissolves in acetone is pyralin sold by Schaff Piano Supply with part numbers beginning with 1380. I cut pieces into quarter inch squares and let is set overnight in the acetone. As for the proportion of acetone/pyralin for hammer hardening, I will leave up to you for experimentation.
    Roger 





  • 12.  RE: keytop solution

    Posted 12-28-2019 12:37
    I was intending to start a thread on an allied subject as some might have experience of ivory keytops and acetone.

    At Christmas I got into trouble from my wife as I'd mended a canteen of cutlery case with CA . . . . and unfortunately some of the bone or ivory handles stuck to the cloth with some glue that had seeped from goodness knows where. I tried using acetone to dissolve the CA sticking the cloth to the handles, and unfortunately the acetone started to attack the bone or ivory too. So I've probably got no solution (forgive the pun) other than mechanical removal, finest sandpaper and shellac polish. But anyone with experience of such things might possibly have some helpful knowledge to share . . . 

    Best wishes

    David P

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    David Pinnegar, B.Sc., A.R.C.S.
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    +44 1342 850594





  • 13.  RE: keytop solution

    Registered Piano Technician
    Posted 12-28-2019 13:00
    Condolences.

    And I can tell you from personal experience that letting CA touch a formica countertop is a bad and irreversible idea.

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    Susan Kline
    Philomath, Oregon
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  • 14.  RE: keytop solution

    Posted 12-29-2019 09:18
    The OP and discussion is focused on acetone/plastic. Ethanol reacts with the hammer and tone differently than acetone, as per Ken Eschete's work on the effect of flashing speeds on where the plastic ends up residing in the hammer. With B-72 (which I do not think is keytop but I think somewhat similar) the acetone, seems to bring the plastic out to the hammer surface as it flashes, leaving the solids on the surface of the hammer. Same B-72 but in ethanol, does not flash the same way, and the plastic remains deeper in the hammer, and more dispersed. 

    In my own experiments with B-72 in acetone and ethanol, ethanol results  in a less harsh, sweeter, easier to control effect. Except in the high treble, I mostly don't need to use it on the crown, except the top half octave. On a well designed treble and good bridge and hammer pinning, hammer shaping, and hammer strike point location, even in the high treble, up to 88, the tone can be excellent with B-72 only at near crown.  Most of the rest of the scale, even with the Bacon felt I use exclusively these days and for the last few years, very little 10-to-11/1-to-2 is needed in select parts of the scale.

    The amount of doping varies according to the belly etc and the quality of Bacon felt Bacon supplies Ray Negron with. The Bacon felt manufacturing can be somewhat uneven batch to batch, so the requirements, set-to-set, vary according to the felt quality. 

    I never use the supply house plastic.

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    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
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  • 15.  RE: keytop solution

    Posted 12-29-2019 11:58
    Thanks for all the help!  I see that the Pianotek hardener pellets are acrylic, so I tried some chunks of some plexiglas I had in the garage.  The web says Lucite is acrylic and Lexan is polycarbonate.  Since the chunks dissolved in acetone I'm guessing they're acrylic.

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    Eric Schell
    ericschellpiano@gmail.com
    Austin TX
    512-363-6236
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  • 16.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 13:26
    While you're at it order some of Pianotek's "Pianolac".  It's a soft setting lacquer (stays rubber when it dries) and tends to not make the fiber so brittle.  You can also use a stronger solution (typically I use anywhere from 15% - 30% depending on the section of the piano and need.  One application of the correct solution is best with strongeer solutions used toward the top and weaker toward the bottom.  Always tread lightly on wound strings at the bottom of the tenor bridge and the top few wound strings on the bass bridge.  End of the bridge effect plus jump in tension on those strings tends to produce a boomy sound which you would be better served by not just having to turn around and needle out.

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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 17.  RE: keytop solution

    Posted 12-29-2019 13:29
    Paraloid B-72 is a resin invented for art conservation.
    Ken Eschete has introduced it for use in piano work, especially voicing.
    Since I can't purchase pure ethanol in North Carolina, I've experimented dissolving it in 99% isopropyl rubbing alcohol and it works well.
    I followed Dan Levitan's protocol: soak B-72 in alcohol for a few days until it is super-saturated, then decant the solution and dilute to taste.
    Test: dip a small strip of paper towel in the solution and let it air dry for a few minutes, then feel the stiffness. Compare the stiffness using a dilute solution. I suggest slightly stiff is plenty enough.
    The result in the hammer will be evident is 15-30 minutes, and you can add more as needed.
    I was incredibly happy with the result in Ronsen Bacon hammers as Jim suggested, and only wish I could go back and redo my past work!
    <https://www.talasonline.com/Paraloid-B-72>

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    Ed Sutton
    ed440@me.com
    (980) 254-7413
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  • 18.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 23:03
    Ed (et al),

    I have not yet tried B-72 with ethanol, but I do carry a bottle of dilute paraloid (B-48?) for voicing.

    I have experimented with using a lower dilution, down to 1% (by weight) of paraloid to acetone.  It is surprising that even this tiny dose will have a significant effect on the brightness of hammers.  In addition, a 1% solution is a lot less likely to "get you in trouble" and is more easily removed or voiced out.

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    Blaine Hebert
    Duarte CA
    626-795-5170
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  • 19.  RE: keytop solution

    Registered Piano Technician
    Posted 12-29-2019 23:06
    Eric,
    One of the orders I made for acrylic came as obviously shredded plastic sheet, probably shredded Plexiglas:
    https://en.wikipedia.org/wiki/Poly(methyl_methacrylate)

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    Blaine Hebert
    Duarte CA
    626-795-5170
    ------------------------------