[CAUT] VS Profelt

[Fred Sturm]

On Nov 7, 2008, at 7:58 AM, rwest1 at unl.edu wrote:

> I remember when methanol treatment of center pin bushings was all  
> the rage.  Methanol certainly works, but I have never been a big fan  
> of it.


	Yes, methanol has a complex history in piano technology. The more  
recent use is specific to Steinway, with the teflon impregnated felt  
bushings. If they are too tight, a very small, controlled application  
of pure methanol dissolves the teflon but leaves it in place, and the  
felt/teflon re-molds itself to the pin, resulting in a free but firm  
bushing. Too much methanol will wash the teflon out of the bushing,  
leaving a spongy mess (probably free, but not firm, wobbly).
	Earlier, methanol was the generally prescribed "wetting agent" for  
"shrinking bushings." Wetting agent means two things: it helps water  
penetrate felt by reducing the electrostatic properties of the water;  
and it dilutes the water, so that a precise proportion of water can be  
applied. "Shrinking" really means "felting" or getting the wool fibers  
to interlock themselves into a denser configuration. Why methanol? I  
think because many years ago it was fairly available at 100% (now,  
with meth labs, it is a controlled substance). Most alcohols available  
50 years ago were mixtures of one sort or other, at some dilution or  
other, and it wasn't very predictable. So if you wanted to do a 10 to  
1 alcohol to water, you needed to make sure you started with 100%  
alcohol. That way, you could try a very small dilution, see what the  
results were, and up the water content if necessary for a second or  
third application until you got the desired result. This is really a  
repetition of factory procedure in making the parts, where the wetting  
process re-packs/re-felts the felt pretty precisely, after it has been  
disturbed during the process of pulling it into the hole in the flange  
and cutting.
	Essentially the function of the methanol in this process is to  
"dilute the water" to a specific ratio, and to evaporate leaving no  
residue.
	Mix these two uses together, and "out in the field" you have  
technicians saying they heard that methanol is a good thing to use for  
center pin bushings. Which really is not very useful information, and,  
indeed, is misinformation unless you know the details. And, frankly,  
some of this "faddish" talk about the miraculous uses of VS Profelt is  
getting to have that same aura of confusion and misinformation.

Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu