What I've learned here is that the restoration of a player piano
requires great effort and is highly dependent on the variable and
increasingly unpredictable quality of certain complex organic materials
like leather, rubberized cloth, and flexible tubing.  That's hardly
a good situation, but it does define an engineering problem that might
be worth addressing on its own.

There are several possible approaches, most of which have been
discussed here:

The use of the most traditional and invariable materials, such as wood
and hide glue, is the most straightforward solution.  Unfortunately,
impermeable membranes don't fall into this category; they are the
product of any number of complex and highly-variable chemical
processes.

The sharing of lore concerning available membrane materials, which is
of course one of the many fine results of the discourse on this list.
Unfortunately, the availability and quality of organic-based materials
can change so drastically as to render previously good advice invalid.

The use of inorganic polymers, such as silicones (I don't know of any
others) would seem to be a reasonable solution except that silicones
are typically incompatible with other organics used in the instruments.
At least this is what I've been able to gather from the discussion
here; there seems to be great grief associated with silicone sealants
bonding wood and leather.

I would speculate, and it's only speculation,  that a fiberglass cloth
impregnated with a silicone resin would likely last about forever in a
player piano whose other materials were compatible with the silicones.
This is not, of course, the case in antique instruments, and it would
seem that there's little point in building stainless-steel-and-
silicone-rubber player actions.

However, it might be worth investigating some sort of silicone/wood or
silicone/leather interfacing material.  I would leave it to the experts
on this list to think of a solution along this line and to analyze the
risks and benefits.  What I'm thinking of is a method in which silicone
rubber membranes would be sealed to, say, a metal foil, and the metal
foil then bonded to wood or leather with hide glue.  I present metal
foil only as a first thought, there must be other materials that could
work.  The labor involved would, however, seem to be very great.

A more straightforward approach along this line would be to search for
a reliable, stable inorganic membrane which could be reliably bonded
with hide glue directly.  I don't know if any such material exists,
though experiments with Mylars and such might be interesting.  I will
concede that a metallized Mylar, even if successful, would look pretty
bizarre amongst the proud old steel cranks and wood chambers.

Finally we come to what, if it works, might be the most practical
solution for the rebuilder: the testing of existing materials.  Samples
of new lots of materials, say rubberized cloth, that are generally
conceded by the restoration community to be reliable over the long term
would be chemically and physically tested by the rebuilder before they
went into a particular restoration project.

This is the most common approach taken in industry.  Every shipment,
every tank car, of every ingredient to be used in a chemical
preparation is individually tested in the laboratory before it goes
into the pills or baby formula or motor oil or whatever.  Now, I don't
know the chemistry involved in determining the quality of, say,
a rubberized cloth or pouch leather, but I strongly suspect that there
are those in industry who do.

How might such testing be accomplished?  I can think of two approaches.
One might be to simply submit a sample of a big roll of rubber cloth
to a reliable testing lab and pay to have it tested.  Given the labor
needed in a restoration job, the fee and delay might (or might not)
be worthwhile.

The other approach would be for the restorer to test a new lot of
material in the shop.  I don't know that this would be as difficult
as it might at first seem to be: many valid tests can be done with a
minimum of apparatus and chemicals.  I would leave the design of such
tests to the research capabilities and resourcefulness of the materials
experts who subscribe to this list.  However, it is likely that there
are industry-standard procedures for the testing of most materials: the
ASTM (Association for the Standard Testing of Materials, or some such)
keeps track of these, and I rather suspect that flexible, impermeable
organic membranes are included.

Even very limited testing -- a quick procedure (say,
temperature-resistance) that won't necessarily  determine the absolute
quality of the material -- may serve to indicate differences in the
chemistry of different lots of material and thus warn the restorer that
all is not well.

Further work along these lines could include research in methods of
'artificial aging.'  In the case of player-piano materials, this might
be done by several months of rapid flexing in an atmosphere that is
high in ozone (which could be supplied by a brush-type motor.)  Some
oil or sulfuric gas added to the atmosphere might further lessen the
time to material failure.

Please be aware that I am taking the position here of 'he who suggests
but cannot do,' i.e., an industrial lab director.  I am neither a
restorer nor a materials researcher, but merely someone who observes
both industry at large and the intense concerns of the craftsmen on
this list.  I can only hope that my elaborate speculations here might
serve to stimulate creative thought on the part of those who understand
the problems at hand far better than I.

Mark Kinsler