Again critics of sponge valves have graced the MMD.  It is a
reoccurring theme here.  I would like to further the discussion just
a bit.

First, it must be agreed that there a several approaches to good
restoration.  Two categories immediately come to mind: traditional
restorations and modern restorations.

In the traditional method, the skilled technician matches each new
rebuilding material to duplicate original materials in both form and
function.  Old rotten leather is replaced with new fresh leather
resembling the original, and so on.

In the other broad category, which I arbitrarily call "modern"
restorations, the technician only duplicates the function of the
restored component, the criteria being that the machine will function
as good as originally intended, but some materials may not be exactly
like the original.  An example of this would be a restored Wurlitzer
theatre organ that functions with a solid-state relay.

It is up to the instrument owner to determine the degree of originality
that should be maintained.  The technician should be able to discuss
with the owner the merits of both types of restorations without making
general condemnations.

With the examples given here in the last few days, about sponge valves
being horrible, it should be clear that the sponge itself is not the
problem.  In one case the obvious culprit is the self-stick adhesive
that was used on the sponge.  These types of adhesives have a
well-known track record of being problematic.

There are other cases in which unit sponge valves are manufactured with
gaps in the .060 inch range.  These valves would work poorly with any
kind of valve medium.  The gap is the big culprit.

Just like some leather is leaky and some leather is tight, the same
quality difference can be found in sponge materials.  High quality
sponge neoprene makes excellent valves if it used correctly.

I started using Neoprene sponge valves, of my own manufacture, in the
mid-1970's.  The material from those early experiments has being laying
around my shop for over twenty-five years, and is still supple.  The
Ampico and Duo-Art pianos, in which those valves were installed, are
still extremely tight and responsive.  The valves are unaffected by
changes in the weather.  The valves operate flawlessly.

During the course of the last twenty-five years I have used both
leather and sponge as a valve medium.  The merits of each were
discussed with the instrument owner and I let them choose which type.
In my own collection, I have both types.

It is my opinion that player pianos and other machines would have
been manufactured with sponge valves had that material been available.
Using organic leather, which will rot and change with the weather, has
it obvious shortcomings.  Which material is used in the space program?
Hmmm.

Bob Taylor

 [ How can one order high quality sponge rubber?  Is there a standard
 [ specification such as ANSI?  -- Robbie