System Three Varnish

[Delwin D Fandrich]

----- Original Message -----
From: "gordon stelter" <lclgcnp@yahoo.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: February 28, 2003 12:03 PM
Subject: Re: System Three Varnish


> Thanks Del,
>     You have plenty more knowledge about building
> pianos than I do, and I virtually cower in your
> virtual presence on most subjects.  However, on this
> particular point I must differ.
>     Spar varnish is, of course, called that because it
> was designed for spars on sailing vessels, which go
> through tremendous dimensional changes due to
> exposure. It has been around long before anything such
> as a "UV blocker" was ever imagined, and contains
> long-drying oils such as raw linseed or such which
> allow it to remain in a very "rubbery", semi-dried
> state for a long period of time, far beyond that
> provided by normal plasticizers. (Which really rather
> relate to aromatic hydrocarbon thinned lacquers,
> anyway, such as nitrocellulose. Aliphatic solvent
> finishes, such as traditional varnishes, generally
> have as resins substances which will not dry brittle
> for decades in and of themselves. )

OK. I bow to your far greater knowledge of chemistry and the history of
varnish. I'm not a chemist--my response came from the answer to an inquiry I
sent to one of the varnish-maker advertisers in WoodenBoat magazine some
years back when I was accumulating information about various finish
materials. I've long ago forgotten which one.

I don't recall any mention being made of the hardness of the coating
material at the time, but, how do you reconcile all this with Jim Bryant's
quote from Wilson Selby & Associates:

<<"ABOUT SPAR VARNISH........ (strictly our opinion)
Spar Varnish has been used for years to provide a super-hard, weather and
water resistant coating for exterior wood. However, this extreme hardness is
not suitable for most exterior wood surfaces on a home.">>

Notice the reference to "super-hard." Not exactly a rubber sheet. And this
tends to go along with my own experiences with modern "spar" varnish. Having
once owned a large wooden boat I got lots and lots of experience with the
stuff. Way more than I ever wanted. Sure seemed to dry hard. Could this be
one of those descriptive names or terms that has changed with the times? Or
is it now--the term--being misused by the manufacturers of the stuff?


>
>      Surely you will agreee that a rubber sheet glued
> to a soundboard would be detrimental to conventionally
> accepted notions of "good tone"?  And that UV
> resistance is hardly a factor we need concern
> ourselves with, as a soundboard put in that much
> direct sunlight would disintegrate far faster than its
> finish  would. ( And anyone who would treat a piano
> like that would probably be tone deaf, anyway! )

While I have never tried coating a soundboard with a rubber sheet, I have
directly compared a number of soundboard finishes including nitrocellulouse
lacquer, interior varnish and exterior varnish (whatever it was in reality
it was labeled "spar" varnish), "natural" varnish and "synthetic" varnish,
2-part synthetic varnish, 2-part polyurethane, uncoated and coated epoxy and
clear polyester. (We're now using a water-borne lacquer, but I've done no
direct comparisons against other finishes.)

All of these finishes were applied to soundboards in otherwise identical
pianos. (OK, they were only as identical as Baldwin could make them in the
late 1980s which may be stretching the definition of "identical" some. But
we did try to average things out by doing some six or ten of each.) In no
case were we able to attribute any tonal change to the soundboard finish
until the coating thickness became a significant percentage of the overall
thickness and/or the coating mass became a significant percentage of the
overall soundboard assembly mass. That occurred with four of five coats of
epoxy and with the polyester (I don't remember the coating thickness).

And, unfortunately, I have encountered altogether too many piano which have
had their soundboards exposed to eiter direct or indirect sunlight during
some part of the day. This being the case, and knowing how epoxy does break
down fairly rapidly when exposed to UV light, I still recommend covering any
coating epoxies applied to soundboards per my PT Journal article with
another finish material containing UV blockers.

Del