Wurzen felt

[John Hartman]

David C. Stanwood wrote:
> Love the conversation about felt and voicing!
> 
> I have to share this quote from a grand master:
> 
> "The art of 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."   Alfred Dolge - Pianos and
> their Makers  1911
> 
> For me hammer felt voicing is all about a balance between hammer weight,
> density gradient, and resiliency.
> 
> Lacquer builds density at the expense of resiliency.  A common problem with
> lacquer is that flooding the whole hammer hardens the surface fibers and
> makes for unpleasent pianissimo tone...  a good lacquer technique is to
> juice the shoulder with lacquer and immediately juice the crown with
> solvent or thin lacquer.   The thinner solution draws the harder lacquer
> out of the shoulder thinning it as it gets closer to the crown creating a
> density gradient while at the same time acting as a resist, keeping the
> harder lacquer out of the crown surface.  
> 
> David Stanwood

David,

You make some good points. As I see it the process of bending the delta 
shaped felt around the molding is to produce this density (stiffness) 
gradient. The real beauty of Lacquer is that you can increase and 
control this gradient at will. Many think that lacquer is used only as a 
last ditch effort to breath life into a dead piano but used this way it 
is an indispensable tool for tone control. No mater how a hammer is made 
it will not have a great enough stiffness gradient to bring out the full 
dynamic range available on a fine quality grand.

The other big advantage to using lacquer is that the hammers remains 
light weight. With modern hammers a heavy felt density is used to 
increase the hammer stiffness. This means there is always a weight 
penalty if you want a stiffer hammer.  It is an endless circle: as 
technicians demand brighter tone the hammers are made heavier and as 
they become heavier their sound become duller. The dynamic range becomes 
smaller and smaller and this is what makes the piano seem less musical.

I think there a limit to how heavy the hammers should be. Practically 
eavery piano I have worked on dating from before WW2 had hammer sets 
that are medium to light in weight. None of them had sets that are as 
heavy as we see today. You would be surprised how many problems, both 
tonally and mechanically, disappear by simply reducing hammer weight. I 
now adjust the weight of each hammer set to work well with each piano. 
With a light to medium weight hammer it doesn't take all that much 
lacquer to improve the stiffness gradient.

I don't see how there is any difference between increasing the hammer's 
resilience by using denser felt or adding some lacquer. Resilience is 
resilience no mater how it's achieved. Everyone wants resilient hammers 
yet felt is not a resilient material.

What I want is control over the hammer's resilience and dampening at all 
the dynamic levels. It doesn't matter if I achieve the desired results 
by needling the felt or by applying a little lacquer.

There are plenty of technicians who declare they never resort to using 
lacquer as if it was some sort of honor. They are missing out on a world 
of possibilities.

John Hartman RPT

John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
Rebuilding Steinway and Mason & Hamlin
Grand Pianos Since 1979

Piano Technicians Journal
Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]