bridge materials

[Ron Nossaman]

I discovered something I thought was sort of interesting the other day.
Tuning a couple of pianos for a small dealer in the area, I was looking at
their Baldwin parts display board on the wall and pulled down the sample of
the grand bridge for a closer look. Looking at it in cross section, I
noticed that each vertical lamination had a slight horizontal (radial)
crack every five or six millimeters the full depth of the bridge. This
bridge was assembled from rotary cut maple!

Observation #1: I quit using the old 11 ply rotary cut pinblock material
years ago because I found that it wasn't trustworthy in locations subject
to wide humidity swings. I've replaced these blocks after as little as four
years in service, and haven't been a fan of thick ply rotary cut stuff in
general since. I assume that the laminations in higher density blocks like
Delignit, Falconwood, and Baldwin's own are also rotary cut, but are thin
enough to have a high enough proportion of glue to wood to be less
problematic. Corrections requested if I'm mistaken.

Observation #2: Folks, when they think of bridges at all, tend to consider
them to be pretty high-tech touchy and supercritical assemblies. While it
seems odd that a major manufacturer would use stuff like this for a bridge
that isn't even capped with a more substantial material, it also seems to
be significant that I don't recall having any more problems with wild
strings and loose bridge pins with this bridge than with most any other,
and fewer problems than some. 

Observations +: I think this is an interesting approach, and I can see some
benefits from a manufacturing standpoint. There is no re-sawing and planing
waste from making strips from larger planks, or the time wasted in doing
so. The surface finish of the laminations prior to gluing are always going
to be rough enough for good glue bonding, unlike planed resaws, which can
come out of the planer with a somewhat burnished surface as the blades
dull. Realistically, they should bend easier too in the lamination cauls.
Ought to be cheaper too.

If anyone has any information on the use, source, and anticipated long term
results of the use of this type of material, I'd sure like to hear about it.

Ron N