I must agree with Craig Brougher's post in yesterday's Digest about
the use of Polylon.

In a large percentage of the pianos which have been through my shop,
there is Polylon in various colors and from various sources which was
installed (although I used PVC-E glue rather than hide glue) as long
ago as 1980, and it's doing fine.

I always glued it poly side in.  Like Craig, if it exhibited any sign
of oiliness or felt otherwise odd, I wiped it down with lacquer
thinner.  I didn't start using it until 1980, so I can't speak to
earlier Polylon.

In my own Ampico there is also Bilon which was installed on the
expression pneumatics in 1981 and it's still perfectly tight, thank
you.  The stack is covered with Schulz cloth and it is airtight and
still performs very nicely at 4.5" of suction.  It was installed with
hide glue the same way Craig does it.

In a pinch, I've been known to run Bilon through the washer with a
degreaser-detergent like Simple Green, although it's probably not the
best way to get rid of the extraneous coating.  (The neighbors also
probably think I'm weird when they see it on the clothesline!)

As Craig suggests, I learned the hard way always to check the material
-- _any_ material -- before I use it.

The reason I started testing the material and the bond was due to some
catastrophic failures years and years ago with Nelson Barden's "Blue
Numalon" (anyone remember that?) and his "Thunder Over Paradise" glue.
Every scrap of that I ever used suffered separation between the nylon
and the polyurethane, along with flaking of the poly layer, after just
a few years of service.

One other major material failure I experienced was with a nylon
motor-cloth from PPCo, which was black cotton on one side and a sort-of
"Papal Purple" on the nylon side.  In a piano which I sent to the
Southern California desert, that became very porous in about 5 years,
although it seemed to test out fine before I used it, and formed a good
bond.  In that case, I'm inclined to place at least some blame on the
heat and dryness of the location since there is some I used here in
Western Washington about the same time that seems to be doing fine.

My only suggestions would be that before _any_ material, or even a new
batch of a familiar material is used, test, test and then test.  I've
probably had more porous or otherwise defective cotton-rubber cloth
than any other variety of pneumatic cloth through the years.  If I can
see "stars" through it when I hold it up to the light, it either makes
a good drawer liner or it goes back to the vendor.

I currently use the imported rubber cloth sold by Schaff and am very
happy with it.  I haven't had a bad batch yet, but I still test each
amount I buy and will continue to do so.

As a side-bar, The Standard Pneumatic Action Company, according to their
old literature, thought that any stack more than 15 years old would
need to have its pneumatics recovered and its valves re-leathered.
With that in mind, I certainly wouldn't get too terribly upset if I
had to recover a set of pneumatics after every 20 years of regular use.
In most cases, by carefully choosing and testing of materials, I
haven't had to do it even that often most of the time.

Listen to Craig Brougher.  He gave very good advice here yesterday.

Dean Randall
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