Re-crowning soundboards

[Delwin D Fandrich]

Kevin,

I suppose you could warp a soundboard by "steaming the top." But it would require that you
maintain that steamy environment to stay warped. Compression crowned soundboards lose
their crown because the wood fibers gradually deform under steady compression -- i.e.,
compression set -- and in so doing they lose their ability to maintain internal
compression within the soundboard panel. So, yes, you could probably induce additional
compression into the board by forcing really large amounts of moisture into the wood
fibers using steam, but you would then have to figure out some method of keeping that
abnormal amount of moisture in there. It's going to want to dissipate very rapidly. Even
if you could do this -- somehow keep that level of moisture in there -- the compression
gained would soon dissipate, again due to compression set. Especially since the rate of
compression set increases with higher levels of fiber moisture content.

Regards,

Del

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Kevin R. Aldrich wrote:

> Del,
>
> Thank you for reminding me of your articles.  I had been thinking, if you
> can flatten a warped piano lid or table top by putting it on a lawn on a
> sunny day, why not warp a soundboard by steaming the top?  The reason why
> not, as I understand it, is that a properly crowned soundboard holds the
> wood fibers in compression.  It is not sufficient to simply have an arched
> soundboard.  Anyway,  I'm not sure it would be possible to put an arch in a
> soundboard that was restrained by ribs and a piano rim.
>
> Kevin
>
> Message text written by INTERNET:pianotech@ptg.org
>
> >Kevin,
>
> This is a simple question with a complex answer. I just wrote a three-part
> article
> recently published in the Journal on the subject. Somewhere in there should
> be the
> information you're after.
>
> Del
>
> ----------------------------------
>
> Kevin R. Aldrich wrote:
>
> > Dear List:
> >
> > Is there a way to restore crown to an old soundboard by applying heat and
> > moisture in some way?  Any information would be greatly appreciated.
> >
> > Kevin Aldrich
> > Aldrich Pianos
> > Troy, NY
> <