Soundboard drydown for installation

[John Delacour]

At 18:29 -0500 18/1/08, Farrell wrote:

>I think this goes back to traditional engineering arch theory. If 
>you dry the board down, it will have a slightly smaller footprint 
>--'Course, none of this actually works - the ribs won't shrink much, 
>the panel top edge will just crush when it expands the 1/10 mm that 
>it might move and the rim has enough flex to negate any "arch" 
>support.

There's drying down and drying down.  The methods used by certain 
makers result all too often in compression marks that can appear even 
before delivery to the showrooms.  On the other hand it seems certain 
that many makers, Bechstein being one of them at least for a long 
time) fitted the soundboard with too high a moisture content so that 
sooner or later in places with dry central heating great cracks 
opened up.  And certain makers (I'm talking here of pre-1910) hit 
upon just the right moisure content for installation so that cracks 
in their soundboards are very rare and always due to excessive baking 
over a long period.

I'd guess that if, as in the case of Stéphane's Ciresa board, the 
board was made to settle with crown at 42% humidity and the board is 
fitted in the same conditions, then there is very little risk of 
cracks appearing, wherever it is sent.  As to compression marks, 
that's mainly a Steinway/Grotrian speciality, and Steinway at least 
work differently from most.  At Grotrian and many other factories the 
board is attached to the inner rim before the outer rim is affixed -- 
not very practical for the restorer but very sensible, in my opinion, 
for the maker of new pianos.

JD