Del,
Is any of the information you posted about the Baldwin block also true
about Falconwood blocks? Aren't they somewhat similar? Just curious.
Avery
>THE CONSTRUCTION & CHARACTERISTICS OF
>COMPRESSED–IMPREGNATED WOOD PRODUCTS
>
>The process used by Baldwin to make their grand piano pinblocks is a
>slightly modified version of one developed during the
>1940's to make a resin-treated compressed wood product known as "COMPREG"
>- or "COMressed, imPREGnated wood. A paper written
>for the U.S. Dept. of Agriculture by the Forest Products Laboratory in
>1951 discussed the development of this process and the
>characteristics of wood based products made in this manner. This material
>was originally developed to form the engine mounts
>(stringers) found in wood hulled mine sweepers. Being non-magnetic, it
>would not trigger the mines that were designed to
>detonate in the presence of ferrous metals. It had the advantage of being
>harder and more reliable than brass in this
>application.
>
>Compreg is a treated wood product that is made of wood and resin-forming
>chemicals (typically phenol- or
>resorcinol-formaldehyde) that act as plasticizers for the wood so that it
>can be compressed under high pressure to a specific
>gravity of 1.0 to 1.4. Several different resins were tried while the
>process was being developed, but the most successful
>was, and still is, water-soluble phenol-formaldehyde resin.
>
>In making Compreg, veneers are treated with water-soluble
>phenol-formaldehyde to a level that will result in a resin content
>of 25 to 30 percent based on the ovendry weight of the wood. The resin is
>allowed to dry without curing at temperatures
>below 30º C (approx. 175º F). The resin is cured later during the heating
>and densification (compression) process. Panels
>are made by heating and compressing the veneers to a specific gravity of
>approximately 1 to 1.4. In the original Compreg
>process, temperatures of 150º C (300º F) and pressures of 1,000 to 1,200
>lbs/in2 were used.
>
>The Baldwin process varies from this somewhat and uses both lower
>pressures and lower temperatures, hence, the density of the
>Baldwin pinblock is lower than the maximum that the process is capable of,
>but it is still quite high.
>
>The resulting material is very nearly a fiber-reinforced plastic (FRP)
>material and has some characteristics that are more
>commonly found in FRP products than it does with wood. Indeed, with the
>exception that kraft paper is used instead of maple
>veneer, the process is very similar to that used to make Formica and other
>such "plastic laminates".
>
>Compreg does have certain characteristics which would seem to make it a
>good material for piano pinblocks:
> 1) It is very stable when subjected to humidity and temperature cycles.
> 2) It resists cracking and splitting.
> 3) It has high compression strength.
>It was probably these characteristics that led Baldwin to use the material
>in the first place.
>
>Unfortunately, it has several other characteristics that, in my opinion,
>make it unsuitable for use as a piano pinblock
>material:
> 1) Springback (after compression), or resiliency, is very low.
> – A material with low springback will simply deform when compressed.
> – When the tuning pin is driven into the pinblock it compresses the wood
> and depends on the woods ability to "springback" to hold it tight and
> maintain good, consistent tuning pin torque.
> 2) Hardness is much higher than normal wood, even maple.
> 3) Impact strength ("toughness") is much higher than that of normal wood, but
> it is very susceptible to the variables of manufacture.
> – The impact strength of the pinblock material is the quality that
>prevents
> the pinblock from being damaged while the pin is being driven
>into the
> tuning pin hole.
> – The reduced impact strength, or toughness, of Compreg allows the
> pinblock to be easily damaged as the piano is being strung.
> 4) Machinability is decreased. It takes on some of the characteristics
>of metal
> and in some cases requires metal working tools for machining operations.
> 5) It is possible to burnish material to a very smooth, glossy surface.
> – This is the characteristic that leads to "jumpy" pins in Baldwin grand
> pinblocks after several years in use.
>
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>- - - - - - - - - - - - - - - - - - - - -
>
>Remember that this was originally written about 15 years ago. Since then I
>spent some time working for the company. And,
>while I did learn a bit more about the details of how this pinblock
>material was made, my opinion of the material and its
>suitability for use as a pinblock did not change very much for the
>experience. Now, if I could just get plate bushings made
>out of this stuff... Ah, well...
>
>Happy New Year one and all.
>
>Del
___________________________
Avery Todd, RPT
Moores School of Music
University of Houston
Houston, TX 77204-4893
713-743-3226
atodd@uh.edu
http://www.uh.edu/music/
This PTG archive page provided courtesy of Moy Piano Service, LLC