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

[Ron Nossaman]

 >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.

Hi Fred,
Actually, I'm somewhat past the experimental stage. This has 
been my choice of cap for four years or so. They are out there 
in pianos, and doing very well.


> 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. 

I've been using epoxy in original bridge caps for 30 years, 
and CA on occasion for over 10. It certainly improves tone 
quality and minimizes false beating, and does seem to narrow 
pitch swings with seasonal changes. I've done testing with 
bridge models of various types, and epoxy or CA saturation of 
at least the cap does improve dimensional stability with 
humidity shifts.

Ron N