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
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