[ Bernt Damm wrote about pneumatic rubber in 181106 MMDigest: ]

"The original stuff must have had something else (secret) in it to make
it last so long.  The same goes for the original gray rubber tubing."

Yes, indeed.  The chemical reactions under discussion here weren't
demonstrated in your chemistry class primarily because human life is
short, and though testing labs have tried over the years to speed up
the testing by subjecting specimens to ozone, ultra-violet light, heat,
cold, and rapid flexure, there continues to be no such thing as
artificial time.

Early die-cast metal alloys in player pianos, and polyurethane resins
in 1970s stereo speakers, famously failed in the past, and probably
something that's holding vital computer semiconductors together will
fail in the future.  So we do our best.

The previous poster's observation about gray rubber hose and old
rubberized cloth is interesting, however, because natural rubber goods
(all pre-WW2 rubber was from rubber trees) were sold in various grades,
depending on the amount and quality of used, de-vulcanized rubber in
the mix.  My 1927 Sears catalog reprint lists three grades of galoshes,
raincoats, and mats.  I'm not sure about tires, but I do know that hot
water bottles were advertised as containing no used rubber.

Rubber goods were extensively recycled at that time.  Used rubber was
called "shoddy," not because it was bad but because that was the name
for the stuff.  I don't recall what the de-vulcanizing process involved,
but apparently it was at least as aromatic as the manufacture of new
rubber goods.  When you were done you could melt down the once-proud
galoshes along with new latex and mold things out of it or spread it
on cloth for player piano builders.

Mark Kinsler