Dear Avery and List,
Thanks for offering me the the opportunity to further expound on a
favorite subject. Sorry for the delay in posting this reply; 'tis the
season to get sidetracked with other things.
The exact ratio of keytop to acetone doesn't seem to be too critical. I dissolve four
APSCO premolded keytops with fronts in a quart of acetone, which
dissolved fully (in a couple of days) becomes my basic "heavy" mixture.
I dilute part of this with an equal part of acetone to create a "light"
mixture.
I don't apply anything to the hammers until I have
heard them in the piano. Since hammer hardening is one of the last steps
in the hammer installation process, let me back up and discuss a few
ideas regarding hammer replacement in Steinways.
First, the
action design and setup. I much prefer the earlier action geometry used
from the 1860s until 1984, with the knuckle placement closer to the
hammer center. When used with the proper weight (light) hammer, this
geometry seems to give the player the greatest control over hammer
velocity, yielding greater possibilities for volume and tone color.
There is a "fork in the road" here, and the technician must really
decide which option to pursue. Option #1 is to install the pre '84,
higher ratio parts along with light hammers. Option #2 is to use heavier
hammers ( or leave whatever hammers are used heavier with less trimming)
and use the later design lower ratio parts. To mix up the combinations
does not work well, especially heavier hammers with the pre '84 parts,
as the touchweight will go way up, requiring lots of key lead to get it back down- the player will have to contend with this lead from then on,
not a happy situation.
My choice is to go with option #1. I know that some technicians feel that
heavier hammers afford the opportunity for greater power, especially on a
concert grand. I respectfully disagree, based on my experience and
experiments so far. One experiment involved weighting some low bass hammers on a Steinway D, by winding solder on the hammershank near the
hammer. It is easy to turn a 10g hammer into a 12, 14 or even 16g hammer
this way. My observations were that the maximum velocities attainable
were sharply curtailed with increasing weight, and the tone became
increasingly dark and lacking in higher partials. There were some pretty
wild string excursions in the fundamental mode with the heavy hammers,
but this did not translate into loud sound. Even on a D, the soundboard
is incapable of creating much sound at the bass string fundamentals, due
to the board's very limited excursion and possibly due to acoustic
cancellation from the 180 degree out of phase radiation from both sides
of the board. Anyway, the 10g hammer worked much better; a much louder,
brighter forte sound, achieved with greater ease by the player.
What seems to work well for me so far is to install the pre '84 Renner
made parts available from S&S on the action frame, which has had both
hammer and repetition rail upholstered with a strip of 3M 320 grit wet
and dry sandpaper. This step greatly simplifies spacing and travelling
of the parts, and avoids later crushed flanges caused by desperate
attempts to make these squirrelly parts sit still on the rail. I add
more thin strips to the top or bottom ledges of the repetition rail as
necessary here or there to achieve the desired action spread. I have
settled in on 4.425" as a good compromise which allows adequate
clearance for the jack in the window.
I like 5 1/16" as a distance from hammer molding center to hammer action
center, as seen on lots of old Steinways. This will work for #1 and #88,
with a straight line in between save for the top two sections, which
benefit from prepared sample hammers glued on every 6 or 8 notes in the
position of best tone. So much is variable in these pianos, and I will sometimes reposition the action frame on the keyframe to get things to
work out well.
The hammers I
favor are the "special order" unbored and unshaped moldings, with only
the cove cut in the tail. I bore them, glue them on the shanks, then remove the assemblies to trim the shanks, shape the tail arc, taper the sides in a straight line from top to bottom, all on a wide belt sander. I
monitor hammer weight during this process by placing each hammer on a
small digital scale after shaping; small discrepancies from one hammer to another can be corrected for with a bit more shaping here or there. I
shoot for a bass hammer weight of 9.5-10g, tapering to about 4.5g in the
high treble.
Next step is the felt
shaping. I like to apply the typical Steinway shape as shown in their
manual. I try not to remove more than a small amount from the crown
(just the squishy, surface layer), then more from the high shoulders to
establish the profile. My theory is that this shape, with it's smaller
radius crown, helps to keep the striking surface of these resilient,
compressible hammers from becoming too broad on a hard blow. Whatever
the reason, they do sound better with this shape applied to them.
I used to subscribe to the theory that a hammer should be softer near the
crown, and become progressively harder toward the center. I'm not sure I
believe that anymore. It all depends on the kind of tone one is pursuing.
An overly soft crown can sound fuzzy and indistinct on a soft blow, and
can choke sustain. A really dense, hard inner core can create a thin, nasty sound on a hard blow; the harder one plays, the less fundamental
remains in the tone, and the more attack noise (thwack! pow! ping!)
becomes prominent.
What
seems to be the greatest strength of Steinway hammers is the way they remain resilient over a very broad dynamic range. With so much felt between the crown and tip of the molding, and all of it low enough in density so
as to allow movement, these hammers will create a huge forte sound which
still sounds round, rich, and beautiful. The trick is to develop the hammers to produce adequate volume and brilliance at low to medium volume
without overhardening them and spoiling their resilience and ability to
handle forte levels. I am beginning to regard the felt mass of the
hammer as a unified whole, and to approach hardening and needling as a
way of making the density and stiffness as uniform as possible
throughout the hammer. This can create a tone which sounds full at all levels, sustains well, and gradually becomes more brilliant ( more high
partials, not less fundamental) with increasing volume as the hammer's
"spring rate" increases as it distorts it's shape under load.
Remember when the Super Ball appeared in toy
stores in the '60's? These small, hard solid rubber balls were great
fun. They would bounce back to 90% of the height they were dropped from,
and I lost several of them because they could bounce clear into the next
block if you weren't careful.
It seems to me that a
piano hammer which embodied the characteristics of a super ball would have some advantages. It would remain resilient over a broad range of
playing volume, and would store energy to push itself away from the strings rather than burdening them with the task of getting rid of the
hammer.
After installing
and shaping a new set of hammers, I take a first listen to them. Usually
they sound too soft throughout, a bit muffled at low volume and incapable
of a loud forte sound. I will generally soak the entire set with the light mixture straight into the crown, penetrating to the underfelt at the
crown and out to about 10 o'clock and 2 o'clock in the shoulders. The
result, once dry in a couple of hours, is more volume and brilliance
throughout. The bass and low tenor may have enough power and brilliance
at this point, or may require some heavy mixture applied to the sides of
the hammer above the tip of the molding to attain enough forte power. If
overdone, the tone will start to acquire the dreaded thin, pingy sound;
this can easily be remedied with some needling through the side in the offending area. The treble, especially the top octave, usually needs
repeated applications of light mixture to develop power. At some point,
I usually needle each hammer through the side midway between the crown
and tip of the molding to maximize sustain. Sometimes a stab or two in each shoulder will help as well.
Soaking into the crown can cause some some pinginess on pianissimo. To fix
this, I'll shallow needle into the crown between the string grooves.
This will also provide some variety of tone for the una corda, without
making the piano owner play for 10,000 hours to develop this quality.
The application of all this hardener may sound alarming
to some, but please remember that I am talking mostly about a thin
mixture of acetone and keytop, not lacquer. To me, this stuff seems to
have the ability to stiffen the wool fibers while preserving their
elasticity. Lacquer seems to freeze the felt solid, which defeats the
purpose of using compressed wool fibers to build the hammer in the first
place. One useful test is to place a hammer between upper and lower front
teeth, and gently bite the shoulders to feel the hammer's resilience. A
hammer developed with acetone and keytop will feel something like a
Super Ball, while the (over)lacquered hammer feels like biting into a
walnut. I never have liked walnuts much.
I hope that some of this rambling proves helpful, Avery.
Hardly any of these ideas are original to me. That is the beauty of PTG
and it's many knowledgeable members. I would really like to hear of your
ideas, techniques, predjudices, etc. as well as those of other list
members regarding all of this fascinating stuff.
Happy Holidays to everyone!
Steve Schell
stfrsc@juno.com
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