Hi All,  Let me preface my remarks by saying that I believe in
'replicating the original' whenever possible.  So, if an instrument
has leather valve seats or valve facings, they should be replaced
with leather.

With regards to sponge neoprene, to say that it's been the downfall
of every player in which it was used is quite debatable.  Having worked
on over 500 modern Aeolian players, including the one I own, I can say
without hesitation that, as inconsistent as the plastic block valves
that Aeolian produced were, the sponge neoprene valve facings have held
up remarkable well.

I just tested an old block that I got when Aeolian closed and it
works fine.  Mind you, it's only 30 years old, but I have customers
who bought their players in the early 1970s and their block valves are
still working just fine.  Personally speaking, I'd say that 40+ years
is a pretty good track record.

Naturally, as is true with most 'modern' materials (stuff that was
first manufactured in the 1960s and '70s), sponge rubber, closed-cell
neoprene, and similar materials have seen numerous improvements.  I've
attached a picture of an old Aeolian facing and the new facing that is
used in the Aeolian replacement block valves that I sell at Player-Care.

It's very easy to see the difference.  The new facing is flat and
smooth -- no open cells on the surface.  The old facing is the same in
the middle as it is on the top and bottom: plenty of closed cells on
the surface.  The new facing is coke-bottle air-tight.  The old one has
a very tiny amount of leakage in a bubble-jar test at 15" WC.  Then
again, so does fine leather.

Now, I'm _not_ saying that sponge rubber or closed-cell neoprene should
be used in place of leather.  What I am saying is, I think it's
inaccurate to lump all such products into a group and then make a
blanket statement about their quality and usefulness.

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA

 [ new and old sponge rubber facings
 [ http://www.mmdigest.com/Attachments/15/02/20/150220_154949_facings.jpg