Felt Quality / Stanwoods tangent

[Richard Brekne]

Hi David,

Thanks for the informative post, I remember a good deal of two lectures 
I've had the pleasure of hearing from you on the subject, but I'm a bit 
sketchy on what you had to say about how lacquer affects hammer 
resiliency. I remember you showing those photos of individual felt 
fibers magnified gawd knows how many times...but I dont remember if any 
of these were of lacquered felt.  You did mention something about 
lacquer binding to felt fibers essentially destroying any resiliency 
each individual fiber has.  Then too was the small <<hooks>> on each 
fiber that end up locking together as part of the felting process, but I 
dont remember what you had to say about how lacquer affects these.  If 
you get time to expound a bit in the same fashion as you did below, I'd 
be very grateful.

Cheers
RicB



    The art and science of felt and hammer making a complex subject for
    sure.  Whether your using cold pressed, hard pressed, lacquered or
    not, the best description of what we all seek is best described by
    the father of the modern production made hammer, Alfred Dolge who
    wrote in 1911 in his book Pianos and Their Makers:

    "The art in hammer making has ever been to obtain a solid, firm
    foundation, graduating in softness and elasticity toward the top
    surface, which latter has to be silky and elastic in order to produce
    a mild, soft tone  for  pianissimo  playing,  but  with sufficient
    resistance  back of it to permit the hard blow of fortissimo playing."

    I'd like to make a comment on Ric's mentioning that Yamaha uses
    Wurzen and  Ray's comment that the Wurzen tends to keep more
    tension...  The Yamaha is a hot pressed hammer and Ronson cold (or
    warm) pressed.  Hot pressed hammers loose tension as a result of the
    heat.  One might imagine heating up a spring that is stretched to a
    nice red glow.  The annealing effect of the heat causes the tension
    to "melt" and when the spring cools off it doesn't take up its
    tension again.  The same is true for hammer felt...  so there is a
    distinction between tension and resiliency.  Wool fibres are more
    resilient than any other natural or manmade fibre unless degraded by
    harsh heat or chemical processing.  So in a hard pressed hammer it is
    a question of restoring resiliency and allowing room for the heat
    densified fibres to move.

    The test of tension is to take a razor blade and cut down through the
    crown of the hammer and watch the immediate effect of the cut opening
    or making a cut through the middle of the hammer molding and seeing
    how the hammer opens.  With a hot pressed hammer the opening force
    from felt tension is always diminished compared to a cold pressed
    hammer.   With a cold pressed hammer the tension then becomes a
    function of the complex structure of the felt and this is very
    difficult to quantify.

    I did have an interesting experience years ago.   I had used a couple
    of sets of cold pressed hammers which had extraordinary tension and a
    most beautiful quality.  I order more sets and found the tension
    greatly diminished.  Nothing the hammer maker did could create the
    tension of the first sets I had ordered.  I sent samples of the fibre
    to Texas A & M for analysis and the only difference found was that
    the average micron diameter of the sets with good tension was 21
    microns.  The sets with the poor tension had an average micron
    diameter of 23 microns.  So in this case fibre diameter seemed to
    have some bearing on the ability of the felt to hold tension at the
    crown.  I have seen fibres diameters of as low as 18 microns in turn
    of the century hammer felts... but it's a complex issue...

    gotta run...

    David Stanwood