[CAUT] dealing with humidity (was Re: pre-stretching new string?)

[Fred Sturm]

On Jun 11, 2007, at 4:34 PM, Dorothy Bell wrote:
> For me, in this discussion, emotions are too high, data too little  
> and gathered in non-standardized manners so therefore not  
> comparable, and applicability of the information to my work is too  
> low.

	The practical side of the discussion (which hasn't been the bulk of  
the discussion, by any means) has to do with how best to treat pianos  
so as to minimize humidity induced "change in tuning." Obviously the  
most reliable approach is to control humidity  in the building, but  
that isn't feasible financially for most, and, from what we hear,  
whole building systems can be unreliable nightmares if not kept  
after. The next approach is to use piano-installed systems, which are  
somewhat, but by no means entirely, effective. Why not? This is where  
this discussion has really focused on something we deal with every  
day. If the "why not" has to do with bridges, as Ron N says (and I am  
pretty well convinced he is right), then perhaps there are ways to  
deal with bridges as well as boards. One way is in design and  
construction, as Ron is experimenting with epoxy impregnated bridge  
caps.
	For those of us who aren't recapping many of our pianos' bridges,  
another possibility is that some degree of saturation of bridges with  
extra thin CA might work to some extent along those lines (making  
bridges less hygroscopically active). Meaning we might go beyond just  
applying a bit next to the pin where there is a false beat, and also  
beyond the capo section. Just a thought, for a line of experiment. A  
first step would be to take an old bridge (or emulation thereof,  
outside a piano) do an application to a portion, leaving another  
portion as a control, and measure expansion and contraction in  
response to humidity change. Variants might include application of CA  
with pins in; removing pins, saturating the hole, replacing pins;  
doing the same with epoxy; epoxy with heat.
	And another possibility is to try to control humidity above the  
board, probably with some variant of a string cover. As has been  
noted, the Edwards string cover, fairly thick wool, has a bit of a  
damping effect. Use of a cloth similar to that provided by Dampp- 
Chaser for undercovers (so-called "speaker cloth" with a loose weave)  
might provide enough isolation to allow for the under-board system to  
create an environment that extends above.
	Anyway, those are a couple thoughts on the practical side. Thoughts  
are cheap. Action and documented results are rare and valuable <G>.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



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