[CAUT] treating bridges for stability

[Cramer, Mark]

I've intended to do a test much like those discussed recently, to see which product penetrated best.

Though I use both epoxy and CA for bridge treatment, some skepticism remains from the days we first discovered just exactly how far pin-block tightener DIDN'T penetrate the pinblock.

Now, with all the interest in testing this stuff, chances seem very good that I can just sit here and wait to read about someone else's results, rather than run the tests myself.  :>)

BTW, I intend to add a bit of colored dye to both the CA and epoxy, so depth would be easy to see.

In addition to testing epoxy cold and heated, I think "thinned: would also make a good test, expecially for cap penetration. Many of us have been using "this" method, thanks to Bill Spurlock's article over a decade ago.  

After some stock has been pinned and treated (i.e. a post-pinning treatment), the pins should be removed, then the stock could be ripped to bi-sect the holes, and the results should be plain as day. 

Any takers?

I'm putting a new shank-slotting jig through the paces, otherwise I could look at this in a week or so.

best regards,
Mark Cramer

PS Be encouraged; the 'process' may be a bit gritty, but we're arguing our way through some very critical technology, stuff most manufacturers are aware of but only a few are presently willing to deal with. We might very well get there first! ;>) 




 
  






-----Original Message-----
From: Fred Sturm <fssturm at unm.edu>
To: College and University Technicians <caut at ptg.org>
Date: Tue, 12 Jun 2007 13:45:19 -0600
Subject: Re: [CAUT] dealing with humidity (was Re: pre-stretching	new	string?)

Sounds like what I have done a number of times. Only in the capo  
section, though, and I've always done it to help clean up false beats  
and get better termination, so I when I did it  I was thinking more  
of "filling in the gap" than "saturating the wood," and was trying to  
keep the surface of the bridge as clean as practical. So I would want  
to change the mind set, maybe leave time for soak in and actually  
paint the surface nice and wet, then clean off excess. I'm thinking  
it would make sense to try the bottom unisons of a tenor bridge, to  
see what effect it might have. Not sure if I can fit that in this  
summer or not, at this point.
	But some experiments with discarded (but not yet thrown in the  
stove) bridges or just some maple emulating them might help in  
developing techniques. Or might show that it really isn't worth the  
bother, if the effect is negligible. How far will CA or epoxy  
penetrate? How much of a vapor barrier will the residue on the  
outside of the bridge be? Probably impossible to answer those  
questions, but at least one could find out how much a bit of bridge  
that was treated expanded and contracted compared with one that  
wasn't treated. (I do know that both epoxy and CA can "penetrate"  
enough to be forced from the bottom of one hole up into the neighbor  
hole, when I pound in a pin. More like being forced through the  
grain, but it means the material has migrated).
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



On Jun 12, 2007, at 12:48 PM, Ron Nossaman wrote:

>
>
>> Hi Ron,
>> When you say epoxy or CA saturation, what do you mean in terms of  
>> method used to saturate? Are these methods one could use on an  
>> existing bridge in a piano?
>> Regards,
>> Fred Sturm
>
> Existing bridges in pianos is what I've done this on forever  
> (though I drive pins in new bridges with epoxy too). First, I  
> always pull the old pins, drill the holes deep enough that the new  
> pin won't bottom out (and size the holes to replace #6 with #7 if  
> they'll fit), and clean up the notches and bridge top. A disposable  
> hypodermic syringe, without needle, to put a dab of epoxy in each  
> hole, and drive in the new pins to finish height. No, I don't  
> bottom them, no, there is no acoustical detriment to not bottoming  
> them that I can detect, and no, I don't file them. Then, depending  
> on how it looks, how the pins felt going in, or if I just don't  
> feel lucky, I'll brush on some epoxy around the pins and heat it in  
> with a heat gun or even a hair dryer. Dry brush mop up the  
> overflow, and a spray coat of McLube to knock the gloss off the  
> epoxy after it's cured. Done.
>
> If you're not replacing pins (*not* recommended) a top coat of  
> epoxy around the pins, heated in until it won't take more, dry  
> brush cleanup, and McLube. Or thin CA, goobered on around the pins  
> until it won't absorb more, mop up with rags, and McLube. No  
> accelerator.
>
> The McLube is strictly to cut the gloss and make the thing look  
> neater than you actually left it. It offers no lubrication benefit.
>
> This will get you the best termination with the least effort of  
> anything I've found, and does indeed seem to improve tuning stability.
>
> Ron N