Bernt Damm was asking what to buy for orchestrion pouch leather.
Usually, skin thicknesses vary anyway. The middle thickness is
probably okay, but not knowing whether this leather supply house spoken
of mikes the edges of the skin, the center of the skin, or takes an
average of several places on a typical skin, would be a question.
The first thing I'd do is to ask how they measure the skins, because
the center of the hide is the thickest. The fringes (belly) will be
thinnest, but also the part most likely to have pinholes and even a
thinness approaching transparency -- which is useless. (Tape it to
a window and mark out these areas first.)
If you want good leather that you can count on, use kangaroo, because
the hide of kangaroo is densest at the surface, which is just opposite
that of sheep. This property allows for practically all of the skin to
be available with very little waste. I believe the PPCo has some in
stock, and it isn't too expensive, seeing as how you can rely on it for
just about everything. Also, you probably won't have to seal it, as it
tends to be tighter than sheep leather. It is many times stronger than
sheep leather. You can't tear it!
As far as thickness goes, that property is important only to the extent
that it makes the pouch leather stiffer. I have seen some rather thick
pouch leather skins which are more supple and draping than thinner
hides, which means that they would make even faster pouches than the
thinner stuff would, and I've proved that out to myself.
Orchestrions don't require as thin a pouch leather as reproducer pianos
would, because they don't work on as low an air pressure as a repro-
ducer. So if your leather is .010 to .015 inch and supple, it will
work for most applications. Sealing it with Dow Corning 111 Pure
Silicone Grease in a solvent, to allow it to flow and evaporate away,
and then talcuming the pouch, will sensitize an over-heavy leather
pouch. Adjusting other parameters, like bleed size and valve stem
distance, will adjust that valve performance, too.
When I could not find decent pouch leather in the early 80's,
I actually restored a Duo-Art with something else: my own version of
nylon pouches. I rested the valves very very close to the nylon/poly
material because they will not ever shrink, kept the dip shallow, was
very critical of valve travel, and adjusted the bleed sizes, and I had
a wonderful piano when I finished. There's more than one way to skin