What is this stuff?  A friend gave me a supply of pneumatic cloths
and leathers that had been put away about 30 years ago and not touched
since.  Everything was in new condition, except for a folded rectangle
of purple wine colored cloth, which was gray on the other side.  The
cloth had a sticky feel to it, and a sour smell.

I checked the MMD Archives and I think it may be "Bilon" or "Polylon"
or some other name, so the first thing is for us to agree on what the
proper names of these cloths are.

If someone says its Bilon and another says its Polylon or something
else, who are we to believe?  Getting the names right is the only way
to classify this stuff.  I figure that by writing in about a purple
cloth that is 0.006" thick and is gray on the other side, people can
write in to tell us what it is and if it should be used or discarded.

Since it seems to me that "Bilon" and "Polylon" are used interchangeably,
let's avoid problems with someone saying "Bilon is bad" when they may
have been seeing "Polylon", and vice versa.

And I'm not the first person to note the awful odor coming off the
stuff -- I assume others can tell what it is by this smell alone.
I think everyone benefits if we know what cloths are good and what
others have fouled up in the past.  No?

My second question is whether this stuff is still usable.  Any opinions
out there about this?

I think that if we started a "materials" section of the Archives,
people will be able to look up what has been written about the colored
plastic cloth that is "color A" on one side and "color B" on the other
side, and is X thousandths thick.

Art Reblitz wrote an article in 1999 listing cloths he has experienced,
but I can't be certain what my sticky and smelly cloth is, and of
course it wasn't so old then.  See

  http://www.mmdigest.com/Archives/Digests/199901/1999.01.27.14.html 

A materials description would also allow you find a certain glue type
when you look at a texture list, such as

1. PVC glue: dries to cloudy gummy rubber.

2. "Elmer's" and many other white glues: dries to a very hard surface,
and is best chiseled off gently.

3. Old fashioned hot glue: dries to brittle hard dark brown.

Randolph Herr