Steinway hammers (long)

[Roger Jolly]

Hi Earl,
         Thanks for such an imformative post, it's greatly appreciated, I
frequently need straightening out, (smile's). It will teach me not to assume.
Kind regards Roger





At 11:41 PM 6/10/98 -0400, you wrote:
>Roger, et al:
>
>At 03:56 PM 06-06-98, the following was written:
>>Hi Newton,
>>          You are quite correct in saying that the volitiles evaporate
>>quicker with the use of acetone, however you are refering to the free
>>acetone molecules, and not the very complex polymer that you have created
>>by melting the keytop STUFF?? The attached molecules of the polymer are the
>>ones that take a long time to be given off.  Since acetone is an alcohol,
>>and is hydroscopic, the RH conditions will have a significant effect on the
>>rate of curing, hence that is why we notice such dramatic effects in this
>>region.
>
>I'm afraid I'm going to reap the reward opposite to being hygroscopic on
>this one, but here goes, as a chemist I can't resist replying:
>
>Acetone is not an alcohol.  It is a simple ketone with the formula, CH3-C=O
>| 
>                                                                            
>                                 CH3
> that is sometimes called "the universal solvent" because it both dissolves
>and dissolves in so many other chemicals.  It is not hygroscopic.  What
>really happens when another chemical dissolved in acetone is applied to
>hammerfelt is that the acetone evaporates so rapidly this evaporation lowers
>the temperature of the acetone not yet evaporated to below the dew point of
>the water in the surrounding air.  This causes airborne water molecules to
>condense on its surface.  And, acetone and water being infinitely soluble in
>one another, this water dissolves in the acetone--you might notice
>indication of this happening by observing a whitish opalescence on the
>surface of the solution.  By the time the remaining acetone evaporates (It's
>more volatile than water.) the wool may have absorbed enough water to remove
>press--release press, if you will. 
>
>>  To correct you on a minor point, laquer thinner is also an alcohol, and
>>is also hydroscopic, and there fore is effected by moisture, and is not
>>impervious, as Steinway may claim.
>
>Chemically, lacquer thinners generally tend to belong to the chemical class
>of esters, but in practice may be a complex solution of many chemicals, e.g.
>toluene, xylene, maybe even higher ketones and other chemicals.  They are
>not hygroscopic as a whole but may evaporate rapidly, which would lead to
>the same cooling effect as acetone, although they likely will not evaporate
>quite so rapidly.  Anyway, the effect is *somewhat* the same:  they pull
>moisture to the surface, and this moisture may be captured by the wool.
>Laquer solvents may cause less of a problem than acetone, however, since
>they are not water soluble.  There will be a blushing problem though, for
>instance, if a wood surface is being coated in a high humidity environment.
>
>> Ask any refinisher.
>>  My practice of always dry ironing after all voicing, helps to over come
>>some of the hydroscopic activity
>>  I think it is the climatical conditions,
>
>Yes, high humidity ambient conditions do tend to exacerbate the moisture
>gathering problem.  And something else:  wool and some other textile fibers
>show the property of hysteresis.  It's a bit hard describing this in words,
>but I'll try since its effects may be encountered by those encountering
>moisture effects on wool.  When damp wool, for instance, that is dried by
>taking the ambient relative humidity from very high to very low, and water
>in the wool is plotted vs. the lowering relative humidity this curve does
>not follow the same path as when the same wool is dried bone dry and then
>gradually brought up in water content by raising the relative humidity of
>the surrounding air. You have to overdo the drying or wetting to get back to
>where you started.
>
>In the situation we're dealing with now this phenomenon means that, when a
>hammer has attracted moisture from the air because it's been chilled below
>the dew point of the moisture in the surrounding air, and this moisture has
>been absorbed by the wool, provided the temperature and relative humidity
>remain unchanged, there will likely be much more moisture in the hammer
>after all the acetone is gone than before the "juicing."  This added water
>will not evaporate unless the air becomes much dryer or the temperature is
>raised a notable amount.  
>
>The hammer maker probably used heat in gluing/pressing the hammer.  This
>removed mosture and added a more or less durable press.  Earlier, the felt
>maker had added also added press to achieve the thickness dimensions and
>hardness the hammer maker specified at given distances from, say, the bass
end.
>
>The more the water gathered in "juicing" and the more the press in the
>hammer (Treble hammers have received much more press to achieve their higher
>density--read that "specific gravity"-- than bass hammers.) the more the
>percentage swell release that can be expected.  If one dries the hammer
>after "juicing," it may help under some conditions, especially if press is
>reapplied, but it is also possible that too much press has been lost by then
>to be replaced by simple ironing
>and the press reapplied will be too little.  Also, the rapid drying, if
>there has been much "juice" added, may well cause the "juice" to migrate
>toward the side of the hammer that is being rapidly dried making it
>harder/crustier.  At this point it must be admitted though that keytop
>material is likely to be thermoplastic and ironing can activate it to hold
>the wool down in place. 
>
>A nasty cycle can develop.  Press is lost, more "dope" is applied because
>the hammer has become too soft, more water is attracted, more press is
>released (along with the resiliency undoped wool provides), more dope is
>added...and so on.  Finally, the hammers are in effect treble keytops:
>really wool-reinforced keytop material!
>
>Sorry if I put you to sleep, folks.  That's what happens when you jostle a
>chemist/textile chemist.  Let me sleep next time.
>
>I await the steam!
>
>Regards,
>
>Earl Dunlap
>Bacon Felt Co., Inc.
>Earl S. Dunlap, Jr.
>Technical Director
>Bacon Felt Co., Inc.
>395 W. Water St.
>Taunton, Mass.
>dunlapes@iCi.net
>
>
Roger Jolly
Balwin Yamaha Piano Centres.
Saskatoon/Regina.
Canada.