Wood

[Delwin D Fandrich]

----- Original Message -----
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: "Pianotech" <pianotech@ptg.org>
Sent: February 15, 2003 1:15 PM
Subject: Re: Wood


>
> > >Why does wood slowly loose its hygroscoptivity over many years ?
> >
> > Does it? Who says so, and on what evidence?
>
> I have it on dietic authority that wood looses its reactionary behavior to
> climatic and anti climatice variations in ambient atmospheric conditions.
I
> thought that was the same thing.

And this authority is? And the context is?

I'm not at all sure it does "[lose] its reactionary behavior to
climatic...variations in ambient atmospheric conditions." If you are
referring to the maxim that, compared to a fresh, new soundboard, an old
soundboard reacts less to changes atmospheric moisture content, this is due
to the amount of compression-set that has taken place in the old board,
i.e., the amount of wood cell damage that has taken place over the years.
Not the mere fact that the wood is older. In my experience old wood that has
not been (that is, has never been) held under stress and has freshly
machined faces pretty much reacts the same as recently cut, but equally dry,
wood of similar species and grain character.


>
> >
> > >And is
> > >there a way of artificially de-hygoscoping wood to begin with ?
> >
> > That's easy - yes. You just have to impregnate it clear through with a
> > catalyzed plastic or resin to make it waterproof. It will no longer be
> > wood, but moisture won't affect it any more.
>
> Ok... but .... is that a good idea or not ? I mean... vhat dost that doeth
to
> its qualities that we are interested in... or easier said... can ya still
> make a good sounding soundboard out of it ? Could you use such "wood" to
make
> a more stable keyframe ? What about such material for a bridge ?

Well, there are other ways of stabilizing wood--saturating the wood fibers
with various preservatives that also tend to displace moisture is one.
Stabilized pressure-treated lumber tends to be somewhat more stable than
untreated lumber because the chemicals involved--chromated copper arsenate
followed by a paraffin injection--tends to bind the wood fibers together and
stabilize them. Of course, exposure to even fairly low levels of chromated
copper arsenate will also kill you in time. And it resists adhesive bonding.
And most finish materials. Other than that, it's really good stuff.

As we continue to refine our epoxy-saturation soundboard coating technique
the results are promising enough that I would have to say, yes, epoxy coated
soundboards have at least some potential down the road.

Besides this, dimensional stability can easily be achieved by laminating
thin veneers together to form panels of whatever thickness is appropriate
for the task at hand. There is no technical reason why soundboards &
bridges, keybeds & keyframes, bellyrails & bellybraces, etc. cannot all be
made out of suitable laminated stock.

Del