Authentic Steinway sound board dilemma

[Delwin D Fandrich]

Danny Moore wrote:
> 
> Delwin D Fandrich wrote:
> 
> > That's the whole point. You don't want a wood finish to "breath."
> 
> Del, list, How, then, does the board continue to react to humidity?  It
> seems that some degree of moisture must be able to absorb and/or
> evaporate from the wood in order to effect the pitch swings that we find
> during the change of seasons and the subsequent change of relative
> humidity?  

Yes this does happen. But, just because something happens doesn't mean
we want it to happen. The ideal soundboard finish would be one that was
totally impervious to water vapor and was perfectly tough and would
protect the soundboard from all forms of physical and chemical damage
and yet would add no mass or stiffness to the board. It should also be
completely environmentally friendly and cost no more than $7.95 a gallon
and have a shelf life of 12 years. Since this material does not yet
exist, it seems reasonable to use the best available material that at
least approaches these goals.


> It addition, it seems that, as the wood continued to age and
> dry, we would notice premature checking and cracking of the finish as
> moisture trapped inside made its way out.  (I once polished out a car
> before all the solvents had flashed off thus trapping them beneath the
> surface - within 2 weeks, it looked like shattered glass!)

If either lacquer or varnish is applied with too thick a film, this can
happen, although not from trapped moisture. If the film thickness is
great enough, both varnish and lacquer can check and crack. I’ve known
several rebuilders that applied both finishes very heavily and then wet
sanded and rubbed out the finishes to a very beautiful satin sheen.
Looked great for a few months, then they started cracking. It’s best to
use the thinnest film practical that is still consistent with the
requirements of providing an adequate vapor barrier. We use a maximum of
three wet coats of clear gloss lacquer.


> Certainly we don't want the radical effect that we would have if the
> board was unprotected.  I had always thought that we used certain
> varnishes and lacquers because they offered the correct "control" over
> the amount of "breathing."  (NOTE:  Breathing may not be the correct
> word for this phenomenon.)

As with the soundboard itself, there is a lot of mythology that has
developed regarding the qualities of the soundboard finish. Mostly, I
think, this has been because the function of the soundboard itself has
been—still is—poorly understood. By the end of the various classes I’ve
taught on soundboard acoustics I’ve sometimes felt like the cartoon
character who, in the middle of a marital dispute, is told, “I don’t
care what you say—It’s going to take more than facts to convince me!”

We don’t want to “control” the amount of “breathing,” we want to stop
it. We just don’t know how to do that without altering the acoustic
properties of the soundboard. Yet.


> If this is not the case, why not use acrylic lacquer?  It works as
> easily as nitro, but is much more resistant to UV.  Or we could use
> polyurethane for an even tougher finish.

The only acrylic I have tested on soundboard samples was somewhat
brittle, although I’ve not looked at them for several years. I’ve used
polyurethane varnishes with some success. I don’t use them in our work
because I don’t like working with them, they are time consuming and they
don’t seem to offer any particular over the lacquer that we currently
use.

However, if anyone having more experience with them would like to add to
our storehouse of knowledge, their comments would be most welcome.


> I realize that toughness and durability are not that big an issue.  It
> seems that most people don't leave their Steinway parked on their
> driveway for extended periods, or at least when they do, they close the
> lid . . .

No, but they do park their new Model B’s in front of south facing floor
to ceiling bay windows that their architect has designed just for the
piano and then refuse to move it because this same architect said it was
OK because he put an air conditioning vent right under the piano to keep
it cool.

ddf