I've been reading with interest this thread about sealing pouches.
I have always sealed my pouches in my restorations.  How do you
design a player action with a certain bleed hole size for leather of
varying porosity?  Seems to me you'd have to have some control over
the porosity before you could determine the right bleed size.  If
pouches were consistently tight you could then say that such and such
a bleed size was optimum.

As far as not sealing at all, I once worked for a pipe organ company
here in Pittsburgh sometime in the 1980's.  I was given the task of
re-leathering an old Austin pipe organ in Epiphany Church next to the
Civic Arena.  The boss and the rest of the crew went to another job for
weeks while I worked on this organ alone.

This organ had the kind of wind chest that allows you to walk upright
inside.  The door was gasketed and you could watch the action work when
the wind was turned on.  Each note had three pneumatics to work the
valve.  You had a primary pneumatic that was about a little bit bigger
than your thumb, a secondary pneumatic that was a little smaller than
a player piano striker pneumatic and then a big power pneumatic about
as big as your hand, that would pull the trace over that opened the
valves.  There was one set of these for each note, 61 notes in each
chest, two swell chests, two great chests and a pedal chest.  Do the
math.

Anyway, I removed all of these pneumatics, took them to my shop and
recovered all of them in tan pouch leather, the same kind you buy for
player pianos, as was done originally.  As an experiment for durability
I recovered one of the small primary pneumatics with the same working
area or a little larger than a standard secondary pouch, with nylon
cloth.

Guess which one of the notes in that organ was the only one that
worked.  The one with the airtight nylon cloth.  I had to remove all
of those pneumatics, take them back to the shop and seal them with
rubber cement (I didn't know the PVC-E trick then) and then reinstall
them.  Then the organ worked.

The wind pressure in the organ was about 4 inches I think; it's been
a long time.  I set up a vacuum cleaner in the shop and held the
pneumatics open against the suction, applied the diluted rubber cement
and then used talcum powder.  They had the same sheen and appearance
that Ampico expression action pouches have when they are first opened.

I seal my pouches.

Tony Marsico
Pittsburgh, Pennsylvania