Authentic Steinway sound board dilemma

[Delwin D Fandrich]

Frank Weston wrote:
> 
> ... You said it yourself.  No common coating except epoxy is impervious 
> to water vapor.  And as you note, you wouldn't want to use epoxy on a
> soundboard.  Being permeable to water vapor is like being pregnant -
> there is no such thing as just a little bit.  Wood under a permeable
> coating will attain a water content in equilibrium with the surrounding
> air, no matter what the coating.


Not so! Not so! There are varying degrees of permeability in various
finish materials and it does matter. Humidity levels do not remain
constant. They fluctuate a great deal, often over a relatively short
period of time. Like on a 24 hour cycle. (Not all pianos reside in the
South where high humidity during the summer months is a way of life.) 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. 

Also, people don’t have to be using their pianos as coasters or coffee
tables to have accidents in their homes. It would be nice if the finish
were able to protect their vintage Steinways from the wear and tear of
daily life.

Otherwise, of course, you’re quite right about the wonders of shellac.

Regards,

ddf