Spencer Chase did stick his neck out with his posting on 030314.
But I, for one, believe there is merit to his posting.  To digress,
the rebuilding of pneumatic instruments has been plagued with
experimentation with faulty new materials.

The miracle pouch material, Perflex, was tried and seemed to be the
"new wave" to replace tan pouch leather.  The trouble was, Perflex,
was never meant to be a pouch or anything like it.  Its hydroscopic
properties soon led to pouch installation failure.  In pipe organs,
this was a huge catastrophe in that redoing all pouches is a mammoth
task.  Then comes the late Aeolian player of the 1970's with its
plastic unit valve containing a sponge valve body.  The valve was
gapped to excess, by design, and the sponge soon turned as hard as
granite.  Those valves were horrible from day one.

So now within the industry, sponge neoprene and plastic pouches
immediately signal emotions akin to the plague.  Joining the two above
new synthetic items is new composite cork-rubber gaskets.  There are
many grades of this material, and, unfortunately, the ones introduced
to the restoration technicians were of inferior quality.

So, after being on my soapbox, Spencer is correct in stating that PVC-E
can be used very effectively.  In fact, it is the best adhesive for
nylon coated pneumatic cloth.  The removal of old PVC-E glue is no big
deal -- like Spencer said, it can be scrapped off.  It can also be
removed completely with acetone.

High quality composition cork gaskets will outlast and outperform
pure cork.  The material I have the most experience with is labeled
"DC-100".  One of the applications of DC-100 is within natural gas
meters.  Unlike pure cork, it will not take a permanent set at clamping
pressure used within player pianos.  It doesn't dry out nor become
brittle.  It is superior to pure cork in every aspect.

High quality sponge gasket material such as SCE-43, with skin on both
sides, is tough and will last for years giving an absolutely air tight
seal, something impossible for leather.  I still have my first sample
of this material which I obtained in the early 1970's.  It is still
supple.

Sponge gaskets, composite neoprene cork gaskets, and PVC-E glue can all
be used without fear of failure if they are high quality products and
they are properly applied.  But, early failures of cheap, inferior
grades of these products have left a stigma that will not be overcome
anytime soon.

First class restorations properly using these materials can be
expected to be almost immune to temperature and humidity fluctuations.
Additionally, twenty-five years after the restoration, the instrument
can be expected to perform as if it were a fresh restoration.

I always give my customers the choice of materials: traditional or
modern.  Most opt for the modern.  I always use hot glue for
wood-to-wood and leather-to-wood.

Bob Taylor