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MMD > Archives > February 2015 > 2015.02.22 > 05Prev  Next

Sponge Neoprene for Valves
By D. L. Bullock

When I responded to the sponge neoprene question, we were talking
about a Duo-Art stack that had it.  This indicated that what was on the
piano was the perfectly awful sponge neoprene sold by Durrell Armstrong
[Player Piano Company] in the 1970s.

When Durrell was pushing that stuff I was young and gullible.  He
convinced me that sponge neoprene was better than leather and I thought
I would try it on my own Duo-Art.  He also convinced me that I should
use Perflex and Polylon on my pneumatics as well.  These new products
(at that time) ultimately turned into a nightmare.

I had to rebuild my Duo-Art stack several times: once to recover
pneumatics with Perflex and then again recover them with Polylon as
the Perflex exploded like balloons when the crash valve came into play.
Then later, after replacing that with blue Polylon that crawled off
the boards of the pneumatics, I tried the red Polylon which flaked off
the cloth.

Then the fourth time was with real pneumatic cloth but since that
was synthetic rubber coating, it only lasted a few years and needed
replacement with natural gum rubber cloth a decade later.  The pouches
were done with Perflex pouches which lasted six years and I had to
rebuild the stack once again to use leather.

The most laughable part of my experiment with Durrell's new high tech,
"forever" synthetic products was the sponge neoprene valve facings.
The cross valves were covered with his sponge neoprene and they worked
amazingly well for a few weeks.  However it got to where I had to open
Accompaniment and Theme levers and snakebites in order to increase
pressure enough for the valves to seal whereupon the piano would play
one roll and then the next roll needed pressurization again to play the

I rebuilt the valves after that with alum leather which was too fluffy
and did not seal because in those olden days we did not test leather
since we thought it was all airtight.  We now know better.  The chrome
tanned leather had to be installed after that and that is on it to this
day.  Luckily I did all the experimenting on my own instruments before
I would use new products on customer's instruments.

Over the years I have replaced all these synthetic products with real
leathers and things function 100%.  I could get nothing synthetic to
work 100% -- it was always a compromise.

That said, I have used the new gray silicone or whatever the gray
sponge valve material is used in the new plastic valve blocks and it is
still functional after nearly 10 years.  I have no problems with it but
there is no comparison with the black sponge neoprene used in Aeolians
and sold by Durrell.

I have restored hundreds of the Aeolian valve blocks using leather
and they work much better than they did from the factory, I suspect.
These original valve blocks had two problems:  (1) the surface of the
sponge would wear away and start to leak and (2) the valve travel was
as high as 100/1000ths inch [0.100"].  The correct travel on these
valves is 0.035" and you never find that on original instruments.

I would suggest the use of John Tuttle's gray valve biscuits for use
on the new and the Aeolian blocks, as long as they can be regulated
to a correct travel.  But I would never suggest anyone could get
acceptable use from the black open sponge neoprene from the 1960s to
the '80s.

Doug L. Bullock

(Message sent Sun 22 Feb 2015, 17:19:05 GMT, from time zone GMT-0600.)

Key Words in Subject:  Neoprene, Sponge, Valves

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