Ref. Pouches: To seal or not to seal... [Dave Krall]

I've come to the conclusion that new pouches must be sealed. I have
friends who have used new leather have with similar problems and
reached the same conclusion -- that sealing is essential.

I rebuilt the primaries on my Pianola grand using the Columbia pouch
leather. At first it had a strange feel about it, pedalling didn't
achieve the expected results. When I reduced the primary travel to the
regular Aeolian .025" I started to get repeats on even quite modest
bridges. The initial wider travel made the primary operation slower
so the playing merely stuttered rather than repeating, a very strange
effect.

I sealed the pouches using natural latex dissolved in naphtha and
the problem vanished. I used the globally-available generic natural
product, not some trade name brand. Latex solution is sold for many
uses, e.g. repairing bicycle inner tubes and for mounting photographs.
It thins readily with naphtha (lighter fluid). I tried a couple of
types, and they differed only in their out-the-tube thickness.

Discussions online have suggested thinned acrylic glue for the same
purpose, but I haven't tried it yet. I can easily see that PVA or
similar glues could be more reliably long-lasting than rubber, but
nothing should be applied in excess. Sealing's sole purpose is to
fill the pores in the leather, a very thin application rather than
a substantial additional layer over the pouch.

The link given in MMD 20.10.26 has a couple of incorrect assertions:

(1) That only Ampico sealed pouches. They may have been the only ones
who advertised the fact, but friends who knew ex-Aeolian staff say they
were told that Aeolian sealed all pouches with rubber. It's likely to
have been common practice and not a matter for discussion, except in
Ampico's advertising. It's the old truism: absence of evidence is not
evidence of absence!

(2) That only reproducing pianos use low suction. This is outright
nonsense. My Pianola will happily work on just about 3 inches, and
needs to if quiet music is to be played. There is literally no
difference between Pianola and Duo-Art pneumatic stacks. I'm sure
not everybody holds on to their player and pedals manically to reach
ear-splitting dynamics, and any rebuilding should be to high-enough
standard to permit the devices to work properly.

Julian Dyer
Wokingham, Berkshire, UK