I must warn my friends that there is, and has been for some time, a good
deal of beautiful-looking but porous pneumatic and motor cloth sold on
the market.  At my shop, we test all pneumatics and bellows under
pressure.  If we can collapse them with their inlets plugged, or if the
cloth comes loose from the pressure, they are rejected.  This easily
reveals any kind of leakage.  After taking the greatest of care in
covering a set of striking pneumatics (we use cold fish glue, as was used
in many of the old factories), I have been horrified to find massive
leakage under test.  After experimentally sealing the edges and boards in
several ways with no result, finally I brushed PVC-E on the surface of
the cloth -- to find that it bubbled!

I first discovered this several years ago, with Schadler's APSCO motor
cloth.  After reporting this dutifully to Ed Jr. ("Schad"), with
photographic documentation of the bubbling glue, I went about my business
expecting the problem to be remedied.  A month later, I ordered another
piece of cloth.  It, also, leaked like a sieve.  Schad's comment:  "Well,
you can't expect us to throw away a $10,000 order of cloth!"  I assume he
continued to sell it, and that APSCO still sells porous cloth if it comes
that way, and if people will buy and use it.

Next I found that Durrell Armstrong's famous "wine colored" cloth leaked
very badly, after covering two sets of bellows to reproducing pianos.  I
also reported this to Durrell.   I assumed that the APSCO episode was
only a fluke, but found that this is an epidemic, as you shall see
presently.

I switched to Schaff's handsome black motor cloth, which holds air
nicely.  This gave me enough comfort that I recklessly purchased four
yards of their nice pneumatic cloth not too long ago, and covered two
sets of pneumatics without testing it.  You may infer the outcome -- this
cloth, unfortunately, is also worthless.

The only remedy, after doing a set with this trash, is to treat them with
PVC-E externally.  If applied undiluted and very thin, this does not
materially increase the resistance to closure and makes them totally
airtight.

The moral of this story is to thoroughly test every scrap of cloth that
you buy, in the way described above.  I wish we could exert pressure upon
our suppliers to improve this product, but I guess we are lucky to get it
at all, in view of how relatively few restorers there are, and how little
material is needed.

Incidentally, I have an original L. J. Mutty 1914 Pneumatic and Bellows
Cloth Sample Book of about 200 swatches -- many in new condition!
Others, seemingly the same weight and type, are badly decayed.  From this
I conclude that those cloths made from more expensive materials cost more
and were sold under different stock numbers.  If only we had their files,
specifying the chemical formulas to each number -- perhaps cloth could be
made which could be guaranteed for over eighty years!

I agree with the comments about the sad state of modern decals, and
assume that only Pierce's collection (old stock) are any good and still
glisten with true gold color.  The original company which sold decals to
Aeolian in the grand old days, was around a few years ago, but I believe
they might be gone now.  They sent me a catalogue and I ordered varnish
transfers from them.

Larry Broadmoore,
Broadmoore Automatic Instrument Restorations
818-365-6231