Compression rigs

[Stéphane Collin]

Thomas,

Thank you for the info.
I think I'm going to replace that board.  The piano is worth it, methink.

Stéphane Collin.

----- Original Message ----- 
From: "Thomas Cole" <tcole at cruzio.com>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Wednesday, June 21, 2006 5:19 AM
Subject: Re: Compression rigs


All the soundboard mavens are gone to Rochester but maybe I can shed
some light.

It looks like the grain has been raised by water contacting the surface
of the wood, as if water had been spilled on it and left to penetrate
the varnish. A compression ridge, on the other hand, is usually formed
at the joint between two "flitches". Judging by what I've seen, the
point where two boards are glued together can be affected by expansion
due to high humidity more readily than within a given board, possibly
because there is a change in the grain angle from one board to the next,
or maybe moisture can saturate the joint more easily than solid wood.

A compression ridge is often visible as a single raised line, which
becomes a crack when it is less humid. But I've seen multiple cracks
near a joint as well.

Tom Cole

Stéphane Collin wrote:

> Hi all.
>
> I join a picture of a 1898 Pleyel concert grand soundboard (close-up).
> Is this what you call compression rigs ?