[ Jan Kijlstra wrote in 070503 MMDigest

> If replacing old rubber tubing in an old instrument (and I guess
> that's what Mark is aiming at) one could think of using silicone
> rubber tubes, disregarding the cost.  The best way, I guess, is using
> "old-fashioned" rubber tubes, in order to keep the instrument in its
> original state as much as possible.

Why would that be the best way?  I would think that silicone rubber
tubes look about the same, and the durability of, say, natural rubber,
is wretched.  Clearly some piano manufacturers weren't happy with the
performance of rubber tubing, or nobody would have tried lead tubing.

The point here is that vulcanized rubber is very much a man-made
product -- it's been called the first plastic -- and thus efforts to
attain dead-solid authenticity are likely doomed to failure: unless
you're going to do a lot of analysis, it's gonna be hard to determine
the sulfur content and the heat treatment time of the old crackly
stuff you just removed.  They put all sorts of admixtures into the
rubber as well, to bulk it out and improve flexibility.  Anyway, it
was my impression that original materials were favored because they'd
withstood the test of time, which rubber clearly does not.

> If not choosing this option alternative tubes can be thought of, and
> regarding the cost there possibly is no use for silicone rubber tubes
> as a replacement for rubber tubes, since PVC tubes are a lot cheaper,
> and will stand up a very long time as well.

But I've read here -- and seen in other applications -- that PVC tubing
can get either stiff, or oily, or both.

My question was whether the restoration people here knew how well
silicone rubber tubing aged.  Given the effort that goes into a
restoration, it would seem that the added cost of silicone rubber could
easily be justified, even though there's an awful lot of tubing in a
piano -- if, of course, it's as stable as I believe it is and there are
no other objections to its use.  (For example, a silicone rubber tube
with acceptable wall thickness might be too flexible to withstand
substantial vacuum.)

> And yes, there is silicone rubber cloth, too.

If it's properly flexible, etc., and if there's a way to glue the stuff,
I would think that this would be worth investigating.  If I recall the
discussions here correctly, you'd want one side of the stuff to easily
adhere to wood using hide glue, the better to get the stuff off in the
event of disaster.

Mark Kinsler

 [ Natural rubber tubing and PVC tubing both depend on added
 [ plasticizer compounds to prevent hardening, but the industry
 [ can't adequately control the properties so there is no
 [ guarantee that the material will remain supple.  Maybe silicone
 [ rubber is better.  -- Robbie