[ Ref. "Sealing Porous Bellows Cloth", 100503 MMDigest ]

Hello again,  After my recent post, I received an e-mail from long-time
MBSI member and friend, Jack Hardman.  He adds a few comments that
should give confidence for using Pliobond.  Note that he mentions that
Pliobond uses MEK as a solvent, so that would work as the ideal thinner,
but acetone seems to work just fine also.  The things I sealed over ten
years ago seem to be just fine.  There is a piece in the MMD Archives
about sealing pouches and the effect of time, here's the URL:

  http://www.mmdigest.com/Gallery/Tech/leakage1.html 

Here's what Jack had to say about Pliobond --

   "We used to be a supplier of 'Pliobond' to Goodyear.  As I remember
 it's a simple solution of butyl (synthetic) rubber and methyl ethyl
 ketone.  It's the butyl rubber and its oxidation resistance and inherent
 tolerance for UV that makes it an especially desirable material to use
 in sealing porous bellows cloth.

   "Natural rubber is a poor choice for 'rubber cloth' even when it not
 exposed to sunlight.  If the makers of rubber cloth would only spend
 another dime, I suspect they could really make a long lasting product
 by incorporating butyl instead of the less expensive natural crude rubber
 (coagulated latex).

   "We made several butyl rubber caulks and sealants.  One was a fantastic
 sealant, made by extruding pure butyl rubber, dusting it with talc so it
 wouldn't stick to itself, and then winding that rope up on a reel.  It
 was applied with a small hand held rubber extruder powered by a Skil
 brand electric drill motor head and gear box to a modified 1" diameter
 wood auger bit running in an electrically heater barrel.  A.O. Smith
 used many of these extruders building their farm silo products.  Others
 were used in the automotive trades for sealing glass for which no molded
 gaskets were available.  Probably most were used in the manufacture of
 insulated glass.

   "We coated the roof of our development lab with a butyl rubber
 membrane to stop recurring leaks.  Great stuff for weather and sun
 exposure!"

Notice Jack's comment about insulated glass.  If butyl rubber can stand
the heat, cold and UV in a thermal glass window, it shouldn't have any
trouble tolerating the climate in a player piano.

Craig Smith