soundboard drying speed ( Thanks Ron ! Details ???)

[gordon stelter]

Great idea. I only wonder what .000 of movement equals
"adequate" drying. And does this thing "wear out" (
lose "elasticity" after several cycles )?
     I do my drying in an aluminum, portable
outbuilding in my backyard. I also do my finishing and
ozoning there, thus displacing some very serious
health hazards. It is 10'x12', which is really not
quite big enough ( but I got a "deal" on it ).        

    Stainless steel sheets on the floor ( from the
"scratch and dent" sale at the steelyard ) keep the
plywood from transferring moisture. As the walls are
aluminum, I can get the RH from 70% to 15% in about 30
minutes, with a Sears room dehumidifier. A hose runs
from the tank to outside, so I don't have to dump it
by hand. ( Some dehumidifiers have a  fitting for
this. )  An air conditioner in one of the windows also
helps dehumidify, while keeping the temperature down
if the sun shines too much. 
     At 15% RH, the cracks open up nicely, but don't
elongate. Yes, some joints also open up a bit ( beam
to rim, about 1/32" ) but I'll get some glue in there.
As I see it, these beams already suffered "compression
set" from the excessive moisture the pianos are
subjected to, here in Georgia, so it's "not my fault".
More importantly, I believe, is that I get my shims (
made from old soundboards ) in nice and tight, in a 
shrunk-down board, so I get a little more crown when
it is re-humidified. And so cracks don't open up
later, along the shims.

     Peace,
     G

--- Ron Nossaman <rnossaman at cox.net> wrote:

> 
> > When you are preparing an old soundboard for
> repairing
> > cracks and refinishing, perhaps for coating with
> epoxy
> > to reinforce, is a slower, gentler drying speed
> better
> > for the board?  Can making a board to desorb too
> > quickly cause fiber damage or other damage?  
> 
> I don't think the rate at which the board gives up
> it's 
> moisture is a problem, but the way by which it's
> induced could 
> very well be. If you're drying it with air that's
> been dried 
> by chilling and condensing the moisture out of it,
> you won't 
> hurt it. Using heat, as most of us do, can damage
> the board. 
> Realistically, an oil filled or ceramic heater under
> the 
> blanket shrouded piano, cooking at 100°F for a day
> will likely 
> get the job done without hurting anything.
> 
>   Knowing what the MC actually is in the panel is
> another 
> problem. When is it ready? A shop made MC gage as
> shown, set 
> on top of the soundboard under the blanket, will
> give you a 
> reasonably accurate idea of the MC of the panel to
> tell you 
> when it's time to proceed.
> 
> Ron N
> 


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