Soundboard bleaching

[Ron Nossaman]

At 02:44 PM 4/27/99 -0500, you wrote:
>Normally, after shimming a cracked soundboard we simply delight in the
>contrast of carefully fitted new spruce shims next to aged soundboard wood.
>However, we are rebuilding a 1926 Heintzman 7' grand and would like to
>achieve more uniformity in color on the shimmed board.
>
>Anyone care to share opinions, experiences, techniques and sources of
>supply re: bleaching of soundboards prior to refinishing?
>
>Best regards,
>
>Stan Kroeker



Hi Stan,
The problem I've found with matching shims to the original soundboard panel
isn't the color difference of the two pieces of wood, per se, but the
difference in light refraction from the different grain slope angles between
the panel and the shim. When you look at the installed shim from one angle
and it matches the panel, then walk around and look at it from the other
side, you will probably find that it won't match from all angles no matter
what you do. Nothing short of painting the original soundboard after the
shim is installed will produce a color match from all viewing angles. This
is also why it's so difficult (read functionally impossible) to lay up a
soundboard panel from scratch that doesn't show dramatic color differences
from plank to plank when viewed from different directions. Individual planks
will also show color changes along their lengths as the grain slope relative
to the surface changes. This is the same phenomenon that makes peacock
feathers that iridescent blue, even though they have no pigmentation. It has
very little to do with the actual color of the wood. Some woods are dark and
dense enough that this isn't a big problem, but spruce isn't homogeneous
enough to be dependably color matched this way without artificial pigmentation. 

The old fellow I worked for when I started in this business once made the
observation that a visible shim proved that the tech actually did some work.
Given the difficulty of hiding shims, I kind of like the philosophy.

 Ron