Authentic Steinway sound board dilemma

[Frank Weston]

Delwin D Fandrich wrote:
> A finish that provides a good—even though, admittedly, not perfect—vapor
> barrier goes a long way toward reducing the extremes of internal
> compression and tension that a soundboard would otherwise be subjected
> to. If the finish is able to resist the movement of water vapor well
> enough, it will slow the wood’s absorption of moisture, often long
> enough to allow the humidity level to return to a more moderate level.
> Both modern lacquers and varnishes are able to do this. Shellac is not.

Del, I don't mean to be argumentative, but this last statement sounds
largely conjectural.  It appears to me that the rate at which
atmospheric humidity changes would have just as great an impact as the
rate at which the surface coating transfers water vapor.  I rely upon
empirical evidence when I draw my conclusions about shellac finishes on
soundboards.  I have encountered many vintage pianos with shellac
finished soundboards that were perfect.  I have in my home/shop now one
1922 Steinway M and one 1912 Knabe B that are good examples.  I have, on
the other hand seen lots of new and old pianos (shellac finished and
otherwise) with badly cracked and ridged soundboards.  Is shellac the
reason some soundboards last?  Maybe not, but there is certainly
evidence that shellac does no harm, and lasts a long time in this
particular application.  

Now I wax poetic:

Little Lac bug in the tree
How kind of you to excrete for me
A substance most wonderous of all I know
with which to coat my Steinway piano

Please stop me before I hurt someone.

Frank Weston