Doing crack

[David Love]

Paul:

I would flip the piano over, open up the crack slightly with a shimming tool
and fill it with slow curing, two-part epoxy mixed with a filleting blend
and colloidal silica (available from West System).  Mix enough silica to get
the consistency you want (so that it is not runny and there is no danger of
it leaching through an unseen opening) and use an artist's palette knife to
force it into the crack.  Overfill the crack slightly and scrape off the
excess at the sides as much as possible.  When the epoxy gets to a firm but
not hard stage, slice off the overfill with a breakaway razor blade (one you
can flex a bit).  Sand lightly and paint a light coating of shellac on the
treated area.

David Love


----- Original Message -----
From: <larudee@pacbell.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: November 13, 2001 7:44 AM
Subject: Doing crack


> I'm working on a 1993 Yamaha G3 that has two cracks in the soundboard.
> One goes all the way through the board, and I'm going to shim it the
> standard way, using the Spurlock method.  The other doesn't go through -
> and here's the strange part - it's from the bottom and doesn't show on
> top.  It's most visible between two ribs, but I can slightly feel it
> forming on the other sides of those ribs as well.  On the other hand,
> there is no failure of the glue joints between the ribs and the board.
> Any suggestions for repairing the second crack without having a second
> shim show on the top surface of the board?  This type of work is not a
> large part of my business, so perhaps this situation is more common than
> I think to those of you who do a lot of rebuilding.
>
> Paul Larudee
>