Sound board dilemma

[Delwin D Fandrich]

Glenn wrote:
> 
> Here's the dilemma:  If he sands the whole board down then the original
> Steinway varnish is gone forever, and soundboard is a much lighter color.
> If he leaves it alone (what he would do if it was his) he said nobody would
> notice because it is under the hinges (he will be putting some sort of
> sealant on the whole board anyway -- short name -- starts with a D).  I
> suggested perhaps sanding the whole board and then putting the same type of
> varnish that yellows the wood slightly and even more with time.  He said
> he's never done this but he would if that is what I wanted.  Whatever he
> uses will be brushed on.
> 
> Any thoughts?  Authenticity is important to me but I do want a sharp
> looking piano.  I even asked for a soundboard decal even though the
> original didn't have one.
> 
> Glenn.

Steinway, like all piano manufactures before nitrocellulose lacquer came
into common usage as a wood finish, used varnish to finish their
soundboards. Shellac was used as a sealer coat under the varnish. Both
materials darken with age. They also deteriorate with time and exposure
to ultraviolet light; they dry out, they become brittle and they develop
hairline cracks. As a result, they lose their ability to do what
finishes are intended to do: that is, protect the underlying wood from
dirt and moisture intrusion. No coating that goes over old varnish is
going to “rejuvenate” it. At least not for long.

Just like there is nothing mystical or magic about old soundboards,
there is nothing magic about old soundboard finishes. If it is no longer
doing its job, take it off and replace it. If authenticity is important,
then use shellac and varnish. All natural resin varnishes and lacquers
will darken—"yellow"—the wood somewhat. Waterborn finishes will not. If
the darker color is important, then use a dark shellac under the
varnish. If a better vapor barrier and higher resistance to ultraviolet
light and air pollutants are more important, then use lacquer.
Acoustically there will be no difference. (Don’t forget to finish the
bottom of the soundboard as well as the top. There will be less damage
from ultraviolet light, but it will still be old and dry and is no
longer able to provide the moisture barrier that it once did. Usually
dry sanding the old finish thouroughly—new varnish will not bond well to
an unsanded old varnish finish—and spraying on a wet coat of new varnish
is sufficient.)

Frankly, I'd worry less about the appearance of the finish and take
another look at—actually, another listen to—the soundboard. Looking at
the appearance of a soundboard is not a reliable method of determining
its performance capability. Soundboards that appear to be structurally
sound and still in possession of beautiful finishes can perform badly
and soundboards with cracks and compression ridges and with badly
deteriorated finishes can still perform reasonably well, though it is
unlikely.

The soundboard in this piano is now 75 years old. Since not even
Steinway has been able to repeal the laws of nature, it is impossible
for this soundboard to have anywhere close to the wave impedance that it
had when it was installed. The mass, of course, will still be the same,
but the “springiness” component of the equation will have decreased
significantly and there is no reliable method of restoring it. 

Within the past couple of years both Glen Hart and I have written
extensively about the deterioration of piano soundboards over time. None
of the principles presented in those articles have changed. All
soundboards over 30 to 40 years old are suspect. Especially those that
have been “compression crowned” as were—and still are—all Steinway
boards. 

Somebody—you, if this is your own piano.—is already putting a fair
amount of time and money into rebuilding this piano. A lot of components
are going into it that will presumably have a life span extending well
into the future. Except for the soundboard which will be marginal, at
best, on the day all the rest of the work is completed.

As may be...good luck with your piano.

ddf