Hi Bernt,  I've run into numerous Wurlitzer block valves made by PPCo
over the years.  Everyone had failed because the Perflex pouch material
had split or ripped open.  This is a well-documented problem with
Perflex, which was also encountered by Story & Clark when they were
still Classic Player Piano Co (Seneca, PA) and the Universal Piano Co
(in Calif.).  (I believe it would be accurate to say that the Perflex
pouch is the Achilles heel in the Universal players.)

Regarding the failed block valves:

In every single case I simply pealed off the back piece of cardboard
(fiber material), removed all traces of the pouch and the plastic ring,
and glued in a leather pouch.  None of the valves have failed since
being modified.

Frankly, I'd stay as far away from synthetic materials as possible.
Glad Wrap was never designed to last for any length of time and it's
doubtful (in my mind) that it will handle the stress of 'working' like
a pouch for very long.  (What puzzles me is why you would choose such a
material in the first place.)

If I were going to make a pouch out of a synthetic material, I would
choose TufTane.  That's what Story & Clark uses in their new roll
playing pianos.  As a TV ad (related to motor oil) in our area says:
"It's been tested".  And that is indeed the case with the Tuftane
pouches.  According to the engineer at Story & Clark, the pouches were
tested with 2 million repetitions.

I also spoke to Durrell Armstrong about how the old Wurlitzer block
valves were made, and he told me that the pouches were sandwiched
between two piece of blotter-type cardboard.  The sides touching the
pouch material were treated with acetone just prior to being affixed to
the material, then heat treated for a few moments.

I also asked him what he thought about using Glad Wrap as a pouch
material and (honesty) he laughed.  He guessed they might last a year
(if that) since Glad Wrap is made to be bio-degradable (for
environmental reasons -- landfills, etc.)

Opinions and Facts from Brick, NJ,

John A. Tuttle
www.player-care.com